Thyroid Eye Disease: Diagnosis and Treatment

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ISBN: 0-8247-0771-0

This book is printed on acid-free paper. Headquarters Marcel Dekker, Inc. 270 Madison Avenue, New York, NY 10016 tel: 212-696-9000; fax: 212-685-4540 Eastern Hemisphere Distribution Marcel Dekker AG Hutgasse 4, Postfach 812, CH-4001 Basel, Switzerland tel: 41-61-260-6300; fax: 41-61-260-6333 World Wide Web http:/ /www.dekker.com The publisher offers discounts on this book when ordered in bulk quantities. For more information, write to Special Sales/Professional Marketing at the headquarters address above. Copyright  2002 by Marcel Dekker, Inc. All Rights Reserved. Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfilming, and recording, or by any information storage and retrieval system, without permission in writing from the publisher. Current printing (last digit): 10 9 8 7 6 5 4 3 2 1 PRINTED IN THE UNITED STATES OF AMERICA

Preface

Graves’ disease has been known as a clinical entity for nearly 200 years. While there is still some controversy about who should be credited with its formal medical description, it is clear that its clinical manifestations and associations were appreciated even in the dark ages. Yet, in spite of its long history and its common occurrence, until the past several decades little was known about the etiology of this disorder. During the past 10 years, more has been learned about this enigmatic disease than in the previous 165 years since Graves and von Basedow published their descriptions. It is now clear that Graves’ disease is one of many autoimmune diseases of uncertain cause. Just why the complex immune surveillance system, which is designed to protect the body from outside challenges, turns against self antigens is not firmly understood; however, a variety of theories have been put forth, including cross-reactive activation mediated by some of those same outside challenges, such as viruses. The immune process is unusual in Graves’ and other such diseases because rather than causing destruction or apoptosis of the target tissues, antibody-antigen interaction causes stimulation of target cell protein synthesis through natural surface receptors. The target antigen is now established as the TSH receptor of the thyrocyte, resulting in hyperthyroidism. Another unusual feature of Graves’ disease is its association with manifestations that seem unrelated to the target tissue. In Graves’ disease, this most notably involves the eyelid and orbital tissues and, less commonly, the pretibial dermis. It remains uncertain just which antigens present the primary target of immune response in the orbit, but to date the unique orbital fibroblast appears to be the principal candidate. As discussed in this volume, TSH receptor proteins have been found to be associated with these cells. Complicating this picture further is the presence of additional antibodies directed against other orbital tissues, implicating both extraocular muscles and their connective tissue sheaths in the process. While the exact role of these muscle antigens is not completely understood, it is well recognized that muscle involvement plays a major part in the overall orbital changes seen in this disease. Once the immune reaction spreads to involve the orbit, a variety of changes ensue that result in both cosmetic impairment and functional disability. The sequence of events is only just becoming clear, emerging from numerous immunological studies. Local iniii

iv

Preface

flammation, alterations in cellular function, proliferation of cellular byproducts, and secondary anatomical changes all seem to play a role in the process. This book is an attempt to update the current state of our knowledge of Graves’ disease. We have invited 64 scientists from 13 countries on four continents to participate in the creation of this volume. These represent many of the foremost authorities in their fields, whose research has contributed to the rapid expansion of our understanding of Graves’ disease and its eye manifestations. Because most of the new accumulating evidence involves the immunological basis of the disease and its extrathyroidal manifestations, we devote many chapters to this aspect of the story. In Parts I and II, we discuss general aspects of the thyroid gland, its anatomy, physiology, and clinical evaluation. Part III covers the immune system, the nature of autoimmune disease, self-tolerance, and the role of inflammatory molecules in the immune process. In Part IV, we discuss a variety of factors in systemic Graves’ disease, such as clinical features, environmental and genetic factors, its association with pregnancy and other immune diseases, and radiation and surgical treatments. Part V focuses on a review of Graves’ eye disease, the immunological mechanisms responsible for the eye changes, the role of the orbital fibroblast, associated muscle autoantibodies, changes in glycosaminoglycan synthesis, the risks of smoking and of radiotherapy of the thyroid gland, histological changes, clinical manifestations, and diagnostic techniques. Finally, Part VI explores a wide variety of treatment options, such as external beam irradiation, orbital decompression, repair of strabismus, correction of eyelid retraction, blepharoplasty, and some of the newer methods of cytokine modulation and soluble TSHR protein synthesis. The terminology applied to the ophthalmic component of this disease has varied considerably over time and from one geographic region to another. More than 30 different names have been used in the scientific literature, most commonly Graves’ ophthalmopathy, Graves’ orbital disease, Graves’ eye disease, thyroid eye disease, thyroid-associated ophthalmopathy, and endocrine ophthalmopathy. Among our authors, 10 different terms are employed. We initially attempted to standardize this book by utilizing a single term. However, it soon became clear that there was no definitive consensus on a preferred term, even among coherent groups such as immunologists or ophthalmologists. It also became clear that no single work could establish a standardized terminology, and despite diverse usage, most workers interested in this disease have been exposed to the literature and are comfortable with the various names that have been employed. In the end, we decided to allow each author to use the terminology with which they were most comfortable. While this volume summarizes our current state of knowledge of Graves’ disease and its eye manifestations, new research is emerging daily. This book should be viewed as an interim report only, subject to change as new evidence is presented. However, it is already clear that the next decade will present new opportunities for treatment and perhaps prevention of this disease, based on immunological modulation interventions. We are indebted to the very many researchers and clinicians who have contributed to the growing understanding of Graves’ disease and its eye manifestations. In addition, we extend our thanks to Mary E. Smith for her help in editing the manuscripts, to Rosalyn Vu for her work in editing and preparing the index, and to Gregg Gayre, M.D., for helping to develop the initial concept of the book and editing the final proofs. Jonathan J. Dutton Barrett G. Haik

Contents

Preface Contributors

iii ix

Part I Introduction 1. Introduction Barrett G. Haik and Jorge I. Calzada

1

2. The Eponymy of Exophthalmos Associated with Thyroid Disease Edward C. Halperin and Brian Quaranta

3

Part II The Thyroid Gland 3. Surgical Anatomy of the Thyroid Gland Mark K. Wax and James I. Cohen

9

4. Thyroid-Stimulating Hormone Receptor Yuji Nagayama

19

5. Laboratory Evaluation of Graves’ Disease Phillippa J. Miranda and Diana McNeill

29

Part III Autoimmunity 6. Basic Concepts of the Immune System R. Christopher Walton

41

7. Mechanisms of Immune Self-Tolerance Jacques F. A. P. Miller

51

v

vi

Contents

8.

Role of Inflammatory Mediators in Autoimmune Disease Johannes M. Van Noort

65

9.

Role of Cytokines in Autoimmune Disease Luba Lopatinskaya, Natasha Nikolaeva, and Lex Nagelkerken

79

Role of Adhesion Molecules in Autoimmune Disease Robert W. McMurray

91

10.

Part IV Graves’ Disease 11.

Overview of Graves’ Autoimmune Disease Anthony P. Weetman

97

12.

Systemic Manifestations of Graves’ Disease Warner Burch

107

13.

Genetics of Graves’ Disease Ratnasingam Nithiyananthan and Stephen C. L. Gough

113

14.

Environmental Factors in the Pathogenesis of Graves’ Disease Thomas H. Brix and Laszlo Hegedu¨s

127

15.

Graves’ Disease and Myasthenia Gravis Michael Weissel

139

16.

Pregnancy and Hyperthyroidism Corinne R. Fantz and Ann M. Gronowski

143

17.

Medical Treatment of Systemic Graves’ Disease Jeffrey I. Mechanick

155

18.

Radioactive Iodide Therapy for Graves’ Disease Leslie J. DeGroot

171

19.

Thyroidectomy for Graves’ Hyperthyroidism Jin-Woo Park and Orlo H. Clark

185

Part V Thyroid Eye Disease 20.

Overview of Thyroid Eye Disease: Immunological Mechanisms Jonathan J. Dutton

199

21.

Orbital Fibroblasts and the TSH Receptor in Graves’ Orbital Disease Armin E. Heufelder and Werner Joba

207

22.

Role of Orbital Fat in Thyroid-Associated Ophthalmopathy Terry J. Smith

215

Contents

vii

23. Eye Muscle Autoantibodies in Graves’ Orbital Disease Masayo Yamada, Audrey Wu Li, Cheng-Hsien Chang, and Jack R. Wall

223

24. Glycosaminoglycans in Graves’ Orbitopathy George J. Kahaly

235

25. The Risk of Orbital Disease Following Radioactive Iodine Treatment Leif Tallstedt

243

26. Cigarette Smoking and Thyroid Eye Disease Luigi Bartalena, Claudio Marcocci, and Aldo Pinchera

251

27. Orbital Anatomy and Graves’ Disease Jonathan J. Dutton

261

28. Histopathology of Graves’ Orbital Disease Alan D. Proia

273

29. Clinical Manifestations of Graves’ Ophthalmopathy George B. Bartley

285

30. Orbital Imaging in Thyroid Eye Disease Eli Chang, Matthew W. Wilson, and Mary E. Smith

301

31. Diagnostic Ultrasound in Graves’ Orbital Disease J. Randall Hughes

309

32. Glaucoma in Thyroid Eye Disease John S. King and Peter A. Netland

319

33. Optic Neuropathy in Thyroid Eye Disease Richard D. Drewry, Jr.

327

Part VI Management of Thyroid Eye Disease 34. Medical Management of Thyroid Eye Disease Gregg S. Gayre

335

35. External Beam Radiotherapy for Thyroid Eye Disease Carol A. Hahn and Edward C. Halperin

347

36. Orbital Decompression: An Overview Robert A. Goldberg

357

37. Fat-Only Decompression for Graves’ Orbital Disease Brian J. Willoughby and Michael Kazim

379

viii

Contents

38.

Practical Management of Strabismus and Diplopia in Thyroid Eye Disease Natalie C. Kerr

389

39.

Botulinum Toxin for Eyelid Retraction in Graves’ Disease Matthew D. Gearinger and Albert W. Biglan

405

40.

Surgical Management of Eyelid Retraction in Thyroid Eye Disease Jonathan J. Dutton

413

41.

Blepharoplasty in Graves’ Disease Stephen J. Laquis, Barrett G. Haik, and James C. Fleming

423

42.

Somatostatin in the Treatment of Thyroid Eye Disease G. E. Krassas

433

43.

Pentoxifylline in the Management of Thyroid Eye Disease Csaba Bala´zs

441

44.

Engineering a Soluble Human Thyroid-Stimulating Hormone Receptor Protein Gregorio D. Chazenbalk

Index

449

457

Contributors

Csaba Bala´zs, D.Sc. III Department of Medicine, Kene´zy Teaching Hospital, Debrecen, Hungary Luigi Bartalena, M.D. Insubria, Varese, Italy

Department of Clinical and Biological Science, University of

George B. Bartley, M.D. Department of Ophthalmology, Mayo Clinic and Mayo Medical School, Rochester, Minnesota, U.S.A. Albert W. Biglan, M.D. Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, U.S.A. Thomas H. Brix, M.D., Ph.D. tal, Odense, Denmark

Department of Endocrinology, Odense University Hospi-

Warner Burch, M.D. Department of Medicine, Duke University Medical Center, Durham, North Carolina, U.S.A. Jorge I. Calzada, M.D. Department of Ophthalmology, University of Tennessee Health Science Center, Memphis, Tennessee, U.S.A. Cheng-Hsien Chang, M.D. Nova Scotia, Canada

Department of Medicine, Dalhousie University, Halifax,

Eli Chang, M.D. Department of Ophthalmic Plastic, Orbital and Cosmetic Surgery, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, U.S.A. Gregorio D. Chazenbalk, Ph.D. Cedars-Sinai Medical Center and University of California, Los Angeles, California, U.S.A. ix

x

Contributors

Orlo H. Clark, M.D. Professor and Vice-Chairman, Department of Surgery, University of California, San Francisco and Mount Zion Medical Center, San Francisco, California, U.S.A. James I. Cohen, M.D., Ph.D. Department of Otolaryngology–Head and Neck Surgery, Oregon Health and Science University, Portland, Oregon, U.S.A. Leslie J. DeGroot, M.D. Department of Medicine, The University of Chicago/Pritzker School of Medicine, Chicago, Illinois, U.S.A. Richard D. Drewry, Jr., M.D., F.A.C.S. Department of Ophthalmology, University of Tennessee Health Science Center, Memphis, Tennessee, U.S.A. Jonathan J. Dutton, M.D., Ph.D., F.A.C.S. Atlantic Eye and Face Center, Cary, and Department of Ophthalmology, University of North Carolina, Chapel Hill, North Carolina, U.S.A. Corinne R. Fantz, Ph.D. Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, U.S.A. James C. Fleming, M.D., F.A.C.S. Department of Ophthalmology, University of Tennessee Health Science Center, and St. Jude Children’s Research Hospital, Memphis, Tennessee, U.S.A. Gregg S. Gayre, M.D. Atlantic Eye and Face Center, Cary, and Department of Ophthalmology, University of North Carolina, Chapel Hill, North Carolina, U.S.A. Matthew D. Gearinger, M.D. Rochester, New York, U.S.A.

Department of Ophthalmology, University of Rochester,

Robert A. Goldberg, M.D., F.A.C.S. Department of Ophthalmology, Jules Stein Eye Institute, UCLA School of Medicine, Los Angeles, California, U.S.A. Stephen C. L. Gough, M.D., F.R.C.P. mingham, Birmingham, England

Department of Medicine, University of Bir-

Ann M. Gronowski, Ph.D. Department of Pathology and Immunology and Department of Obstetrics and Gynecology, Washington University School of Medicine, St. Louis, Missouri, U.S.A. Carol A. Hahn, M.D. Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina, U.S.A. Barrett G. Haik, M.D., F.A.C.S. Department of Ophthalmology, University of Tennessee Health Science Center, and Division of Ophthalmology, Department of Surgery, St. Jude Children’s Research Hospital, Memphis, Tennessee, U.S.A.

Contributors

xi

Edward C. Halperin, M.D., F.A.C.R. Department of Radiation Oncology and Department of Pediatrics, Duke University Medical Center, Durham, North Carolina, U.S.A. Laszlo Hegedu¨s, M.D. Department of Endocrinology, Odense University Hospital, Odense, Denmark Armin E. Heufelder, M.D. Department of Endocrinology and Molecular Medicine, Clinical Research Center, Munich, Germany J. Randall Hughes, B.S., R.D.M.S. Department of Echography, Center for Excellence in Eye Care, Miami, Florida, U.S.A. Werner Joba, M.D. Department of Endocrinology and Molecular Medicine, Clinical Research Center, Munich, Germany George J. Kahaly, M.D., Ph.D. tal, Mainz, Germany

Department of Medicine, Gutenberg University Hospi-

Michael Kazim, M.D., F.A.C.S. Department of Ophthalmology, Columbia University College of Physicians and Surgeons, New York, New York, U.S.A. Natalie C. Kerr, M.D., F.A.C.S. Departments of Ophthalmology and Pediatrics, University of Tennessee Health Science Center, and Division of Ophthalmology, Department of Surgery, St. Jude Children’s Research Hospital, Memphis, Tennessee, U.S.A. John S. King, M.D. see, U.S.A.

University of Tennessee Health Science Center, Memphis, Tennes-

G. E. Krassas, M.D. Department of Endocrinology and Metabolism, Panagia General Hospital, Thessaloniki, Greece Stephen J. Laquis, M.D. Department of Ophthalmology, University of Tennessee Health Science Center, and Division of Ophthalmology, Department of Surgery, St. Jude Children’s Research Hospital, Memphis, Tennessee, U.S.A. Audrey Wu Li, M.D. Department of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada Luba Lopatinskaya, M.D. Division of Immunological and Infectious Diseases, TNO Prevention and Health, Leiden, The Netherlands Claudio Marcocci, M.D. Pisa, Pisa, Italy

Department of Endocrinology and Metabolism, University of

Robert W. McMurray, M.D. Division of Rheumatology/Molecular Immunology, University of Mississippi Medical Center, and Rheumatology Section, G. V. (Sonny) Montgomery VA Hospital, Jackson, Mississippi, U.S.A.

xii

Contributors

Diana McNeill, M.D., F.A.C.P. Division of Endocrinology, Metabolism, and Nutrition, Department of Medicine, Duke University Medical Center, Durham, North Carolina, U.S.A. Jeffrey I. Mechanick, M.D., F.A.C.P., F.A.C.E., F.A.C.N. Division of Endocrinology, Diabetes, and Bone Disease, Department of Medicine, Mount Sinai School of Medicine, New York, New York, U.S.A. Jacques F. A. P. Miller, M.D., Ph.D., D.Sc. Department of Immunology, The Walter and Eliza Hall Institute of Medical Research, Royal Melbourne Hospital, Victoria, Australia Phillippa J. Miranda, M.D. Division of Endocrinology, Metabolism, and Nutrition, Department of Medicine, Duke University Medical Center, Durham, North Carolina, U.S.A. Yuji Nagayama, M.D. Department of Pharmacology 1, Nagasaki University School of Medicine, Nagasaki, Japan Lex Nagelkerken, M.D. Division of Immunological and Infectious Diseases, TNO Prevention and Health, Leiden, The Netherlands Peter A. Netland, M.D., Ph.D. Department of Ophthalmology, University of Tennessee Health Science Center, Memphis, Tennessee, U.S.A. Natasha Nikolaeva, M.D. Division of Immunological and Infectious Diseases, TNO Prevention and Health, Leiden, The Netherlands Ratnasingam Nithiyananthan, M.B., Ch.B., M.R.C.P. versity of Birmingham, Birmingham, England

Department of Medicine, Uni-

Jin-Woo Park, M.D. Department of Surgery, University of California, San Francisco, and Mount Zion Medical Center, San Francisco, California, U.S.A. Aldo Pinchera, M.D. Department of Endocrinology and Metabolism, University of Pisa, Pisa, Italy Alan D. Proia, M.D., Ph.D. Department of Pathology, Duke University Medical Center, Durham, North Carolina, U.S.A. Brian Quaranta, M.D. Department of Ophthalmology, University of Tennessee Health Science Center, Memphis, Tennessee, U.S.A. Mary E. Smith, M.P.H., R.D.M.S. Department of Ophthalmology, University of Tennessee Health Science Center, Memphis, Tennessee, U.S.A. Terry J. Smith, M.D. Division of Molecular Medicine, Harbor-UCLA Medical Center, Torrance, and UCLA School of Medicine, Los Angeles, California, U.S.A.

Contributors

Leif Tallstedt, M.D., Ph.D. Sweden

xiii

St. Erik’s Eye Hospital, Karolinska Institute, Stockholm,

Johannes M. Van Noort, Ph.D. Division of Immunological and Infectious Diseases, TNO Prevention and Health, Leiden, The Netherlands Jack R. Wall, M.D., Ph.D., F.R.C.P.(C) sity, Halifax, Nova Scotia, Canada

Department of Medicine, Dalhousie Univer-

R. Christopher Walton, M.D. Department of Ophthalmology, University of Tennessee Health Science Center, Memphis, Tennessee, U.S.A. Mark K. Wax, M.D., F.A.C.S., F.R.C.S.(C) Department of Otolaryngology–Head and Neck Surgery, Oregon Health and Science University, Portland, Oregon, U.S.A. Anthony P. Weetman, M.D., D.Sc. Division of Clinical Sciences, Department of Medicine, University of Sheffield, Sheffield, England Michael Weissel, M.D. Clinic for Internal Medicine III, University of Vienna, Vienna, Austria Brian J. Willoughby, M.D. Department of Ophthalmology, Columbia University College of Physicians and Surgeons, New York, New York, U.S.A. Matthew W. Wilson, M.D., F.A.C.S. Department of Ophthalmology, University of Tennessee Health Science Center, and St. Jude Children’s Research Hospital, Memphis, Tennessee, U.S.A. Masayo Yamada, M.D. Second Department of Internal Medicine, Yamanashi University, Yamanashi, Japan

1 Introduction BARRETT G. HAIK University of Tennessee Health Science Center and St. Jude Children’s Research Hospital, Memphis, Tennessee, U.S.A. JORGE I. CALZADA University of Tennessee Health Science Center, Memphis, Tennessee, U.S.A.

The association between thyroid disease and exophthalmos has been recognized for more than three centuries. Scholars from different parts of the world attribute the first modern description of the syndrome to Caleb Parry in England, Robert James Graves in Ireland, or Karl Adolph von Basedow in Germany in the late 18th or early 19th century. Since the time of these early accounts of thyroid-associated eye disease, our understanding of this syndrome has advanced significantly. In general terms, it has been noted that patients who either have or eventually develop autoimmune thyroid disease can present with multiple ophthalmological complaints, ranging from mild corneal exposure and eyelid retraction to malignant exophthalmos with corneal perforation or compressive optic neuropathies with severe vision loss. Several studies indicate that these problems are caused by lymphocytic infiltration in the orbit, primarily in the extraocular muscle tissues, and deposition of mucopolysaccharides, glycosaminoglycans, and collagen (1). Although our understanding of the syndrome has greatly increased, a number of issues regarding nomenclature, pathophysiology, and treatment are yet to be elucidated. Fundamentally, there is still disagreement over the correct name and terminology that should be used to refer to the condition. At least three eponyms have been used to refer to autoimmune hyperthyroidism with exophthalmos, Graves’ disease being the most commonly used on the American continent. Other names that have been used include endocrine exophthalmos, exophthalmic goiter (2), thyroid eye disease (3), Graves’ ophthalmopathy, Graves’ orbitopathy (1), and thyroid ophthalmopathy (2). A consensus is yet to be reached. Controversies regarding the management of patients with Graves’ ophthalmopathy also exist. We still cannot predict which patients with any form of autoimmune thyroid 1

2

Haik and Calzada

disease will develop significant ophthalmic problems. There are, however, indications that smoking tobacco and radioactive iodine treatment for Graves’ hyperthyroidism can increase the risk of ophthalmopathy. Advances in imaging technology have greatly improved the ability of ophthalmologists to differentiate inflammatory orbital changes associated with Graves’ ophthalmopathy from orbital tumors, and have reduced the need for surgical biopsy to confirm the diagnosis. Ultrasonography, computed tomography, and magnetic resonance imaging each play a specific role in the diagnosis and monitoring of patients with ophthalmopathy, and each modality has specific strengths and limitations. Despite these advances in imaging technology, the diagnosis and management of these patients still depend primarily on a thorough clinical examination. While the therapy for the hyperthyroidism associated with Graves’ disease is fairly successful, the current treatment options for the ophthalmological manifestations have numerous shortcomings and are frustrating at times for the treating physician. The treatments are mostly supportive, addressing primarily the symptoms of the disease and not its causes. Most patients with Graves’ ophthalmopathy have external eye complaints that are self-limited and usually managed with lubrication and topical therapies. Patients who develop severe orbital inflammation, proptosis, diplopia, and compressive optic neuropathies require more aggressive therapy. Many ophthalmologists use systemic steroids, either oral or intravenous, for short-term control of the disease. Most patients show some response to the steroids, but a subset of patients either do not respond adequately or have significant side effects that warrant stopping the steroids. There are different options for treatment of these patients, but there is no definite consensus on the most appropriate. Immunosuppressive medications have also been used, some with limited success, and others, like cyclosporine, with potential benefits. Surgical orbital decompression or external beam radiation therapy may be warranted in patients with compressive optic neuropathies to prevent significant loss of vision. Another important issue in the management of these patients is the control of the sequelae after the inflammation has subsided. The management of diplopia and strabismus secondary to extraocular muscle inflammation or fibrosis can be challenging. The cosmetic effect and corneal exposure resulting from eyelid retraction are often a major concern of these patients and may require surgical correction. In the patient with complex disease, it is often recommended that orbital decompression be performed before proceeding to extraocular muscle surgery. Eyelid surgery is often deferred until both of these other procedures are done. The aim of this book is to present an updated and comprehensive appraisal of the basic and clinical aspects of Graves’-associated ophthalmopathy. We do not expect to settle all the issues that surround Graves’ disease, but this multidisciplinary review will at least be a step in that direction. REFERENCES 1. Coday M, Netland P, Dallow R. Thyroid-associated ophthalmopathy (Graves’ disease). In: Albert D, Jakobiec F, Azar D, Gragoudas E, eds. Principles and Practice of Ophthalmology. Philadelphia: WB Saunders, 2000:4742–4759. 2. Duke-Elder S, MacFaul PA. Orbital involvement in general disease. In: Duke-Elder S, ed. System of Ophthalmology, Vol. XIII. St. Louis: CV Mosby, 1974:935–968. 3. Char D. Thyroid Eye Disease, 3rd ed. Boston: Butterworth–Heinemann, 1997.

2 The Eponymy of Exophthalmos Associated with Thyroid Disease EDWARD C. HALPERIN Duke University Medical Center, Durham, North Carolina, U.S.A. BRIAN QUARANTA University of Tennessee Health Science Center, Memphis, Tennessee, U.S.A.

The association of hyperthyroidism with exophthalmos is not uniformly recognized by the eponym “Graves’ disease.” Depending upon where a physician trained and practices, exophthalmic goiter may be referred to as Parry’s disease, Graves’ disease, von Basedow’s disease (morbus Basedow), or the Merseburg triad. All of these eponyms have a sound historical basis. I.

PARRY’S DISEASE

The first description of exophthalmic goiter is probably that of Caleb Hillier Parry (1755– 1822) (Fig. 1). Sir William Osler considered that “if the name of any physician is to be associated with the disease, undoubtedly it should be that of the distinguished old Bath physician” (1). Parry was born in Gloucestershire, England, studied medicine in Edinburgh where he graduated in 1777, and practiced in fashionable Bath. He went to school with Edward Jenner, who remained a lifelong friend and dedicated his famous book on vaccination to “C. H. Parry, M.D., at Bath, My Dear Friend” (Fig. 2). Parry developed a large practice at Bath and became the most prominent physician at the resort (2,3). Parry’s account of thyroid enlargement and exophthalmos was published posthumously by his son in 1825. The first case of this coincidence which I witnessed was that of Grace B., a married woman, aged thirty-seven, in the month of August, 1786 . . . About three months after lying-in, while she was suckling her child, a lump of about the size of a walnut was perceived on the right side of her neck. This continued to enlarge till the period of my attendance when it occupied both sides of her neck, so as to have reached an enormous size, projecting forwards before 3

4

Halperin and Quaranta

Figure 1 Caleb Hillier Parry, M.D., F.R.S. (1755–1822). (From Ref. 13.)

Figure 2 Dedication page from Edward Jenner’s textbook, An Inquiry into the Causes and Effects of the Variolae Vaccinae, a Disease Discovered in Some of the Western Counties of England, Particularly Gloucestershire, and Known by the Name of the Cow-pox. London: printed for the author by Sampson Low, 1798.

Eponymy of Exophthalmos

5

the margin of the lower jaw . . . the eyes were protruded from their sockets, and the countenance exhibited an appearance of agitation and distress, especially on any muscular exertion, which I have rarely seen equalled (4).

Although the work was not published until 1825, the case described was seen in 1786, making it the first documented case history connecting exophthalmos and goiter. As is often the case, the importance of this work was not fully realized until years later. Even then, Parry’s name was for some time misspelled as “Percy” in major publications because of a clerical error (5). II. GRAVES’ DISEASE Robert James Graves was born in Dublin, Ireland, on March 28, 1796. He was the son of the Reverend Richard Graves, Regius Professor of Divinity at Trinity College, Dublin, and Dean of Ardagh (Fig. 3). His mother was Elizabeth Drought, daughter of another professor of divinity at Trinity College. One of his ancestors was Colonel William Graves, a cavalry officer who came to Ireland with Oliver Cromwell in 1650 and was given an estate in County Limerick as a reward for his military service. Young Robert Graves was tutored by an uncle of Oscar Wilde. He graduated with highest honors, receiving the Gold Medal, from Trinity College. He qualified in medicine in 1820. Graves continued his postgraduate training with 3 years of travel. He studied in

Figure 3 Robert James Graves (1796–1853). (From Ref. 13.)

6


London, Go¨ttingen, Berlin, Copenhagen, and Edinburgh. So impressive was his fluency and mastery of German that he was taken for a German spy in Austria and imprisoned for a few weeks. Graves returned to Ireland and was elected physician to the Meath Hospital in Dublin in 1821. Within 2 years, he was elected a Fellow of the Irish College of Physicians. In Dublin, he introduced the continental system of clinical teaching, which required the students to examine patients and write clinical histories rather than rely almost entirely on lectures and book knowledge. Graves also made contributions to our understanding of angioneurotic edema, intermittent pallor of the fingers and toes (a decade before Raynaud), scleroderma, the importance of timing the human pulse with a watch, pinpoint pupils in pontine hemorrhage, and abandoning the practice of bleeding and starving patients with fevers. He was quoted, “Lest when I am gone you may be at a loss for an epitaph for me, let me give you one—he fed fevers.” In 1827, he became King’s Professor of the Institute of Medicine, the first full-time Chair of Medicine in Ireland. His most important work, Clinical Lectures on the Practice of Medicine, was published in 1848. Graves described the disease with which we associate his name in the London Medical and Surgical Journal for Saturday, May 23, 1835 and in his clinical lectures at the Meath Hospital in the 1834–35 session (2,3,6,7). A lady, aged twenty, became affected with some symptoms which were supposed to be hysterical . . . the eyes assumed a singular appearance, for the eyeballs were apparently enlarged, so that when she slept or tried to shut her eyes, the lids were incapable of closing. When the eyes were open, the white sclerotic could be seen to the breadth of several lines, all around the cornea . . . a tumour, of a horseshoe shape, appeared on the front of the throat and exactly in the situation of the thyroid gland. This was at first soft but soon attained a greater hardness though still elastic (8).

Graves died of cancer of the liver on March 20, 1853, just short of his 57th birthday. Graves’ paper was slow to draw a response but figured prominently in the later publications of his colleague at the Meath Hospital, William Stokes. Graves’ name was first used in association with the disease in 1860 by the French physician Trousseau, a great admirer of Graves’ lectures (2).

III. VON BASEDOW’S DISEASE, BASEDOW’S DISEASE, OR THE MERSEBURG TRIAD Karl Adolph von Basedow (1799–1854) was born in Dessau to an aristocratic German family (Fig. 4). He studied medicine at the University of Halle. After surgical training in France, he returned to Germany in 1822 to practice in Merseburg, near Leipzig. He practiced as a surgeon and general practitioner and had a strong interest in pathology. His 1840 description of the occurrence of exophthalmic goiter and palpitations in hyperthyroidism is named, in his honor, the Merseburg triad (2,3). Madame F., brunette, well built, of a decided phlegmatic temperament . . . In the neck there appeared a strumous swelling of the thyroid gland . . . As far as the eyes were concerned, they were pushed out so far that one could see below and above the Cornea, the Albuginea, three lines wide; the eyelids were pushed wide for one another; could not be closed with every effort. The patient slept with the eyes entirely open (9,10).

Eponymy of Exophthalmos

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Figure 4 Karl A. von Basedow (1799–1854). (From Ref. 12.)

Von Basedow recognized that the exophthalmos was due to an increase in tissues behind the eye. He hypothesized that dyscrasia of the blood caused this swelling as well as the goiter (11). Von Basedow’s paper was considered to be the most comprehensive description of the disease at the time and was accompanied by a thorough review of the literature. His work went ignored for some time. In a publication in the same journal 8 years later, the German physician, Henoch, proclaimed “Nowhere do German physicians mention this striking symptom-complex.” Von Basedow’s contribution was more enthusiastically received to the west, where the French physician Charcot first suggested the name “maladie de Basedow” in 1859 (5). Unfortunately, von Basedow died 5 years before this honor could be bestowed, after contracting typhus during an autopsy.

IV.

OTHER EPONYMS

By 1908, Dock (5) had catalogued 21 different appellations, and to this day the name taught to medical students depends greatly upon the location of their school. Among the names not commonly used today is “morbido di Flajani,” a tribute to the paper published in 1802 by Giuseppe Flajani of Ascoli (12). The name was suggested in the late 1880s by several Italian physicians, claiming that Flajani was the first to publish a case of the later recognized syndrome. Many sources credit Flajani’s paper as describing

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exophthalmic goiter. However, in his careful evaluation of the paper, George Dock notes that neither of Flajani’s patients had exophthalmos. One of the two patients had goiter associated with dyspnea, palpitation, and weight loss, but Flajani attributed these to respiratory compromise caused by the tumor and by frequent bleedings. The other patient had goiter with no other symptoms described. It is concluded by Dock that “it does not seem rational to continue to refer to Flajani as a contributor to the knowledge of exophthalmic goiter” (5). In the early part of the 20th century, the disease was known to some in America as “Parsons’ disease,” as reflected by the use of that title in four American dictionaries of the time. The attribution is to James Parsons (1705–1770) who lived earlier than any of the other physicians associated with this malady. While he was the author of 31 papers, there is no evidence that any of these dealt with thyroid disease (5). V.

CONCLUSION

Parry, Graves, and von Basedow each provided elegant and dramatic descriptions of exophthalmic goiter. Other early 19th-century physicians also may be credited with descriptions. For those who feel that eponyms add to the romance and history of medicine, those associated with Parry, Graves, and von Basedow are equally appropriate. REFERENCES 1. Poster MF. Thyroid eponymy. N Engl J Med 1973; 288:422. 2. Major RH. Classic Descriptions of Disease with Biographical Sketches of the Authors. 3d ed. Springfield, IL: Charles C Thomas, 1978. 3. Sebastian A. A Dictionary of the History of Medicine. New York: Parthenon Publishing, 1999. 4. Parry CH. Collections from the Unpublished Medical Writings. Vol. II. London: Underwoods, 1825. 5. Dock G. The development of our knowledge of exophthalmic goiter. JAMA 1908; 14:1119– 1125. 6. Taylor S. Graves of Graves’ disease, 1796–1853. J R Coll Physicians London 1986; 20:298– 230. 7. Havard CWH. Medical eponyms updated: 2, Graves’ disease. Br J Clin Pract 1990; 44:409– 410. 8. Graves RJ. Newly observed affection of the thyroid gland in females. London Med Surg J 1835; 7(2):516–517. 9. von Basedow K. Exophthalmos durch hypertrophic des zellgewebes in der augenhohle. Wochens Ges Heilkd 1840; 13:197. 10. von Basedow K. Die glotzaguen. Wochens Ges Heilkd 1848; 49:770. 11. Hennemann G. Historical aspects about the development of our knowledge of morbus Basedow. J Endocrinol Invest 1991; 14:617–624. 12. Rolleston, HD. The Endocrine Organs in Health and Disease with an Historical Review. London: Oxford University Press, 1936. 13. Herrick JB. A Short History of Cardiology. Springfield, IL: Charles C Thomas, 1942.

3 Surgical Anatomy of the Thyroid Gland MARK K. WAX and JAMES I. COHEN Oregon Health and Science University, Portland, Oregon, U.S.A.

I.

INTRODUCTION

The surgical management of thyroid disease was described as early as the 1800s (1). Infection leading to sepsis and hemorrhage was frequently encountered. Perioperative mortality was common. It was not until Theodor Kocher perfected his technique of thyroidectomy that the mortality rate dropped to an acceptable level (1). Since then, refinements in medical management, anesthesia, and infection control, and an improved understanding of surgical anatomy have resulted in a rapid decrease in morbidity (2–8). The thyroid gland lies in the central compartment of the neck at its junction with the upper mediastinum. The gland is intimately related to the recurrent laryngeal nerves, parathyroid glands, trachea, and esophagus (2,5,6,8). Experience and a thorough understanding of these anatomical relationships will allow the surgeon to have an acceptably low rate of reversible or irreversible functional problems in the perioperative period (5,7). This chapter will focus on the anatomy of the thyroid gland from a surgical perspective, describing the relationships of the various structures that surround, or are near to, the thyroid gland. This will allow the reader to understand the causes of the most common complications encountered in thyroid surgery. In addition, it will describe the anatomical basis for a technique of thyroidectomy that highlights, acknowledges, and respects these relationships so that complications are avoided. II. EMBRYOLOGY A complete understanding of the embryological development of the thyroid gland is important. Important structures adjacent to, or intimately involved with, the thyroid gland estab9

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lish specific relationships as a result of their embryological development. When anatomical variants are encountered, the surgeon who has an understanding of the embryology will also understand the implications of, and ramifications for, other associated structures. The thyroid gland originates from epithelial cells in the midline of the floor of the pharyngeal anlage´ (9,10). Early on, the pharyngeal anlage´ descends in the midline and divides into two lobes. By around the seventh week, it comes to rest anterior to the trachea below the cricoid cartilage. In the normal course of development, the thyroid gland will weigh about 20 g. It appears soft and uneven in outline. A smaller bridge, the isthmus, connects the two lateral lobes. The isthmus can be palpated over the trachea, between the cricoid cartilage and the sternal notch as a rubbery transverse ridge approximately 1–11/2 cm wide. The lateral lobes are 4–5 cm in height, 1–2 cm in thickness, and 2–3 cm in anterior/posterior width. Abnormalities of thyroid descent result either from a persistence of the thyroglossal pathway (11) or from a failure to descend properly (12). Thyroglossal duct cysts are the most commonly encountered midline neck masses. Ectopic thyroid secondary to nondescent is extremely rare. When it occurs, ectopic thyroid gland can be located anywhere from the foramen cecum (the remnant of the pharyngeal analogue) to the midline of the upper trachea (9,10). Understanding both of these anatomical abnormalities is important when evaluating patients with midline neck masses to ensure that removal of a neck mass thought to be a thyroglossal duct cyst does not result in removal of the entire thyroid gland. Preservation of parathyroid gland function represents one of the major challenges in thyroid surgery. The incidence of permanent hypoparathyroidism following total thyroidectomy is 2–3% on average (5,7,8). Patients who experience permanent hypoparathyroidism have significant morbidity and require lifelong supplementation with vitamin D and calcium. An understanding of embryology is therefore of the utmost importance, as it determines the anatomical relationship between the parathyroid glands and the thyroid capsule and helps in their identification when operating on the thyroid gland (9,10). The parathyroid bodies arise as endodermal cell proliferations at the lateral tips of the third and fourth pharyngeal pouches. The third pharyngeal pouch gives rise to the third parathyroid and to the thymus. As the fetus develops, the thymus migrates inferiorly to its resting place in the upper mediastinum. Because of its relationship and attachments to the thymus, the third parathyroid descends along with the thymus. Its final resting place can be anywhere from the posterior thyroid capsule to the upper mediastinum. The fourth branchial pouches give rise to the ultimobranchial bodies. These develop into the parafollicular C cells that are eventually incorporated into the lateral lobes of the thyroid gland. The relationship between the parathyroid derived from the fourth branchial arch and the ultimobranchial body is responsible for the close association between the parathyroid and the superior pole of the thyroid gland. This developmental pathway is also responsible for the more consistent location of the superior parathyroid (Fig. 1a, 1b). The recurrent laryngeal nerves are the other major structures at risk during thyroid surgery (2). Although they do not provide any innervation to the thyroid gland itself or impact on its homeostatic function, their function is integral to the larynx. Injury to the recurrent laryngeal nerves is a major and feared complication of thyroidectomy. Temporary recurrent laryngeal nerve paralysis occurs at a rate of between 0.5 and 3.9%, while the incidence of permanent recurrent laryngeal nerve paralysis varies between 0 and 3% (3–7). An understanding of the embryology and development process of the vagus nerve allows the surgeon to be prepared for the various anatomical abnormalities that may be present.

Surgical Anatomy of the Thyroid Gland

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Figure 1 (a) This anatomical drawing depicts the location and relationship of the superior parathyroid gland to the thyroid gland. (b) Here we see the possible locations of aberrant parathyroid glands based on their embryological descent.

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The fourth and sixth branchial arch cartilages fuse to form the laryngeal cartilages (9,10). Each of these branchial arches is supplied by its own nerve. The vagus (tenth) cranial nerve supplies the fourth to sixth branchial arch. The fourth branchial arch receives its predominant supply from the superior laryngeal branch of the vagus, while the recurrent laryngeal branch supplies the sixth branchial arch. Associated with these branchial arches are six pairs of branchial arteries. The various branchial arches form and disappear at various intervals. Not all are present at the same time. The left fourth aortic arch forms part of the arch of the aorta, and the right fourth aortic arch becomes the proximal part of the right subclavian artery. The fifth pair of branchial arches is either rudimentary or never develops. The proximal part of the left sixth aortic arch persists as the proximal part of the left pulmonary artery, whereas the distal part becomes the ductus arteriosus. The proximal part of the right sixth aortic arch persists as the proximal part of the right

Figure 2 Relationship of the recurrent laryngeal nerve to the thyroid gland, parathyroid glands, and the tracheoesophageal groove. Note the insertion into the inferior constrictor with extra laryngeal branching.


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pulmonary artery, whereas the distal part degenerates. Because the recurrent laryngeal nerves hook around the sixth pair of aortic arches on their way to the developing larynx, their course becomes different on the two sides. On the right side, as the distal part of the right sixth and fifth aortic arches degenerate, the right recurrent laryngeal nerve moves superiorly to hook around the right subclavian artery. By contrast, the left recurrent laryngeal nerve cannot migrate superiorly as it is held by the ductus arteriosus, which becomes the ligamentum arteriosus after birth. Because of these differences, the anatomic relationships of the inferior thyroid artery may be variable. The recurrent laryngeal nerve enters the larynx through the inferior constrictor muscles. A variable branching pattern can be present, with most nerves bifurcating or trifurcating more than 5 mm inferior to the cricoid cartilage (2,3,5,6) (Fig. 2). Malformations of the aortic arches that result from the persistence of parts of the aortic arches that normally disappear or from the disappearance of parts that normally persist may alter the position of the recurrent laryngeal nerve (11–14). An abnormal origin of the right subclavian artery will cause the right recurrent laryngeal nerve to arise in the neck and pass directly to the larynx (13). The incidence of right nonrecurrent laryngeal nerves varies from 0.35 to 1.5% (13). When this occurs, the nerve can form a deep horizontal notch in the posterior surface of the thyroid gland and become intimately associated with the capsule of the gland. In some cases of situs inversus viscerum, the left recurrent laryngeal nerve may also arise in the neck.

III. SURGICAL ANATOMY AND TECHNIQUE A. Incision Placement Concern about the scar associated with thyroidectomy is an issue of primary importance to the patient. This concern has led to descriptions of so-called minimally invasive approaches by which thyroidectomy is performed through a very small incision or in a closed manner using laparoscopic instrumentation (16,17). In reality, a small (3–5 cm) incision, appropriately placed and repaired, results in minimal cosmetic deformity and sensory loss. It affords adequate exposure for safe performance of the operation. The sensory nerve supply to the skin of the lower neck comes from below and laterally. The lower an incision is placed, the more minimal the sensory deficit will be. We have found that a horizontal incision, centered on the midline and placed at approximately the level of the cricoid in a skin crease with the patient’s head extended, works well. After elevation of the skin flaps, the incision is retracted from side to side to afford adequate exposure. Gland size and the location of the abnormality within the thyroid gland must be considered in incision design rather than using a “one-size-fits-all” approach. Skin flaps are elevated to the level of the hyoid bone superiorly, sternal notch inferiorly, and to the anterior border of the sternocleidomastoid muscle (SCM) laterally. Elevation beyond these points does not increase exposure; the limiting factor then becomes the strap muscles. The plane of elevation is the superficial layer of the deep cervical fascia, which is best identified by ensuring that one is deep to the platysma laterally and that the anterior jugular veins are deep to the plane of elevation. Sensory innervation to the upper midline skin of the neck is through the sensory branches of the cervical plexus that run over the anterior border of the sternocleidomastoid muscle at approximately the level of the thyroid cartilage notch. Elevation beyond this at the lateral aspects of the incision does not help exposure.

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Gland Exposure

Although exposure of the thyroid gland is predominantly a “midline” exercise, certain maneuvers can facilitate this. The superficial layer of the deep cervical fascia tethers the lateral attachments of the strap muscle. This restricts the degree to which they can be retracted laterally. We therefore begin by incising the fascia along the anterior border of the SCM from the level of the thyroid notch to the sternum, avoiding the sensory branches that cross superiorly. The sternohyoid muscles are then split in the midline from the level of the hyoid to the sternum. We begin inferiorly where they are more dehiscent. They are elevated off the underlying sternothyroid muscle. The fascia at the lateral border of the sternohyoid is then divided. This circumferentially skeletonizes the muscle and allows it to be retracted laterally with the SCM muscle. The superior attachment of the sternothyroid muscle to the thyroid cartilage restricts exposure of the superior thyroid pedicle if the muscle is only retracted laterally. Because this places the external branch of the superior laryngeal nerve at risk for injury, we prefer to divide the sternohyoid muscle between clamps, completely incising its medial and lateral fascial attachments and elevating it off the thyroid capsule all the way to its insertion superior in the thyroid cartilage and inferior in the upper sternum. This facilitates superior thyroid pedicle exposure. This degree of strap muscle elevation usually results in division of the ansa cervicalis/hypoglossi nerve to these muscles as it inserts into the lateral border of the muscles. This has not been found to be a significant problem in terms of voice or swallowing and is considered to be a reasonable trade off for the exposure and safety it affords (18,19). In patients with a long thin neck or a small thyroid gland, a more limited elevation with ansa preservation may be performed (Fig. 3). The descent of the thyroid gland and its “fusion” to the laryngotracheal complex as it develops means that the gland is tethered superiorly, medially, and posteriorly by fascial attachments. Systematic and appropriate sequential division of these attachments affords the best exposure and delivery of the gland without its surrounding structures such as the parathyroids and recurrent laryngeal nerves. There are three possible fascial planes of dissection when working around the thyroid. The middle layer of the deep cervical fascia, which surrounds the entire thyroid and laryngotracheal complex, represents the first and most lateral plane. While the easiest to work in, it should be avoided, as it will result in the inclusion of the superior and often the inferior parathyroid glands. The recurrent laryngeal nerve and inferior thyroid artery run in this fascia and may be damaged. Another plane, the most medial, is within the thyroid capsule itself. It is also best avoided because it represents a more difficult and vascular plane. The preferred plane of dissection is between these two. This plane is on the thyroid capsule itself but leaves the parathyroids and recurrent nerves behind. It is entered by dividing the superior and inferior venous pedicles of the thyroid at the gland capsule and connecting the openings that this creates. When working in this plane, small venous pedicles must be divided. Generally the inferior thyroid artery and its branches, the parathyroids, and the recurrent laryngeal nerves are easily identified and left undisturbed (20). C.

Superior Pedicle Exposure

After sternothyroid muscle elevation, the larynx is retracted medially and the plane between it and the medial aspect of the superior pole of the thyroid is opened. Working


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Figure 3 This anatomical drawing depicts the relationship of the thyroid, parathyroid, and recurrent laryngeal nerve to the major vascular structures that run nearby.

from superior to inferior the fascia between the thyroid and larynx is divided and the external branch of the superior laryngeal nerve is visualized where it crosses from lateral to medial to innervate the cricothyroid muscle. The relationship of this nerve to the superior thyroid pedicle is variable and its identification is necessary prior to division of the pedicle. This is accomplished just inferior to it where it crosses (21–23). After superior pedicle division, the lateral fascial attachments of the thyroid lobe and (if present) the middle thyroid vein are divided immediately adjacent to the capsule. D. Inferior Pedicle Division Beginning medially just below the isthmus, the fascia that attaches the thyroid to the trachea is divided. The window thus created in the fascial attachment of the thyroid to the laryngotracheal complex is then expanded laterally, dividing the venous pedicles right on the thyroid capsule itself. The inferior parathyroid gland often sits immediately deep to these veins and derives its venous blood supply from them. These same veins often drain into the upper thymus, reflecting the embryological connection of these two structures (20). If the veins are divided too low and away from the thyroid capsule, the inferior parathyroid gland can be inadvertently removed with the thyroid. Once the inferior aspect of the thyroid lobe is freed up, this plane of dissection is connected to the one created by division of the superior pedicle and middle thyroid vein, and the thyroid lobe is rolled forward to expose its posterior capsule.

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Posterior Capsule Dissection

With the gland rolled forward, the dissection proceeds in a vertical plane on the capsule, dividing the many small veins that are carried with its fascial attachments. The superior parathyroid gland is often seen on the capsule carried forward by its venous attachments to the posterior capsule and reflecting the embryological association between the two structures. Careful division of these veins is important but often will result in temporary venous congestion of the gland and temporary dysfunction (20). If identification of the other parathyroid glands has been difficult and their function is in question, preservation of superior gland function is best assured by incising into the capsule anterior to the venous attachment of the parathyroid gland and leaving a small amount of thyroid gland posterior to it in place. This constitutes the anatomical and physiological basis for so-called neartotal thyroidectomy, which is designed to preserve parathyroid rather than thyroid gland. Because most parathyroid glands do not derive the majority of their blood supply from the thyroid capsule, total thyroidectomy is possible without parathyroid compromise. F. Recurrent Laryngeal Identification As one proceeds posteriorly along the capsule, the issue of recurrent laryngeal nerve identification becomes important. The recurrent laryngeal nerve has a variable relationship to the distal branches of the inferior thyroid artery, which enter the posterior capsule at this point and therefore begin to appear in the field of dissection (24,25). These branches can carry the nerve forward along with the posterior capsule where it can be injured if it is not identified. Therefore, at the point where these arterial branches are first encountered the nerve must be found. There are two methods of nerve identification. One is to find the nerve lower in the tracheoesophageal groove and trace it antegrade up to its entry into the larynx. The other is to find the nerve at the point of entry into the larynx and trace it retrograde to the degree necessary to prevent injury. The latter technique is preferred for the following reasons. With the former technique, the nerve position is more variable, both in terms of the normal anatomical differences between the right and left side (see discussion of embryology above), as well as in the degree to which the nerve is distorted by forward rotation of the thyroid during the dissection. The small distal branches of the inferior thyroid artery, which supply the parathyroids, may also be disrupted by necessary dissection of the nerve. Finally, if the nerve branches divide early and the more anterior branch is not appreciated, the latter may be injured. By contrast, with retrograde identification and dissection, the position of the nerve at its point of entry into the larynx is less subject to variation and therefore identification can be more precise. The inferior cornu of the thyroid cartilage serves as an easily palpable landmark for this point of entry. The nerve enters the larynx through the lateral cricothyroid membrane just anterior to this point and varies very little in position because its point of entry tethers it. Retrograde dissection of only 1 cm of the nerve is necessary to protect it from injury at its most vulnerable point. Anterior branches are also more easily seen and protected by this approach. G.

Division of the Suspensory Ligament/Removal of the Isthmus

With the nerve identified, all that remains to release the thyroid lobe from its last fascial attachments to the laryngotracheal complex is division of the suspensory ligament of the thyroid. This tethers it to the lateral cricoid lamina and trachea. The attachment of this


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thick fibrous band always lies anterior to the nerve (26,27). However, small distal branches of the inferior thyroid artery often run deep to the nerve and can cause troublesome bleeding or nerve injury if cautery is attempted. In addition, in large goiters the suspensory ligament can on occasion be infiltrated by thyroid tissue that extends deep to the nerve, making total thyroidectomy without nerve injury difficult. With sectioning of the ligament just anterior to the nerve, the thyroid lobe will roll forward and release itself from the trachea. The recurrent laryngeal nerve will fall back as the trachea rotates back into its normal position. Superior parathyroid, if not already identified, can be found superior and lateral to the point of nerve entry into the larynx. If total thyroidectomy is planned, the above procedure is repeated on the contralateral side. The isthmus and its superior fascial attachments now suspend the gland. These reflect its embryological descent and any residual thyroglossal duct tract. This tract is followed from inferior to superior up to the hyoid bone where it is amputated. Complete dissection of this tract from inferior to superior will ensure removal of any residual thyroid tissue in a pyramidal lobe or thyroglossal duct tract.

IV.

CONCLUSION

Familiarity with the embryology and anatomy of the thyroid gland allows for its safe removal and avoidance of complications, regardless of the disease process or anatomical variations that are encountered.

REFERENCES 1. Halsted WS. The operative story of goiter: the author’s operation. Johns Hopkins Hosp Rep 1920; 19:71–257. 2. Steinberg JL, Khane GJ, Fernandes CMC, Nel JP. Anatomy of the recurrent laryngeal nerve: a redescription. J Laryngol Otol 1986; 100:919–927. 3. Martensson H, Terins J. Recurrent laryngeal nerve palsy in thyroid gland surgery related to operations and nerves at risk. Arch Surg 1985; 120:475–477. 4. Riddell V. Thyroidectomy: prevention of bilateral recurrent nerve palsy. Results of identification of the nerve over 23 consecutive years (1946–69) with description of an additional safety measure. Br J Surg 1970; 57:1–11. 5. Karlan MS, Catz B, Dunkelman D, Uyeda RY, Gleischman S. A safe technique for thyroidectomy with complete nerve dissection and parathyroid preservation. Head Neck Surg 1984; 6: 1014–1019. 6. Premachandra DJ, Radcliffe GJ, Stearns MP. Intraoperative identification of the recurrent laryngeal nerve and demonstration of its function. Laryngoscope 1990; 100:94–96. 7. Lore´ JM, Banyas JB, Niemiec ER. Complications of total thyroidectomy. Arch Otolaryngol Head Neck Surg 1987; 113:1238. 8. Schwartz AE, Friedman EW. Preservation of the parathyroid glands in total thyroidectomy. Surg Gynecol Obstet 1987; 165:327–332. 9. Moore KL. The Developing Human: Clinically Oriented Anatomy. 4th ed. Philadelphia: WB Saunders, 1988. 10. Gray SW, Skandalakis JE. Embryology for Surgeons. Philadelphia: WB Saunders, 1972. 11. Haddad A, Frenkiel S, Costom B, Shapiro R, Tewfik T. Management of the undescended thyroid. J Otolaryngol 1986; 15:373–376. 12. Ellis PDM, Van Nostrand AWP. The applied anatomy of thyroglossal tract remnants. Laryngoscope 1977;87:765–770.

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13. Mra Z, Wax MK. Nonrecurrent laryngeal nerves: anatomic considerations during thyroid and parathyroid surgery. Am J Otolaryngol 1999; 20:91–95. 14. Sanders G, Uyeda RY, Karlan MS. Nonrecurrent inferior laryngeal nerves and their association with a recurrent branch. Am J Surg 1983; 146:501–503. 15. Henry JF, Audiffret J, Denizot A, Plan M. The nonrecurrent inferior laryngeal nerve: review of 33 cases, including two on the left side. Surgery 1988; 104:977–984. 16. Bellantone R, Lombardi CP, Raffaelli M, Rubino F, Boscherini M, Perilli W. Minimally invasive, totally gasless video-assisted thyroid lobectomy. Am J Surg 1999; 177:342–343. 17. Miccoli P, Berti P, Bendinelli C, Conte M, Fasolini F, Martino E. Minimally invasive videoassisted surgery of the thyroid: a preliminary report. Langenbecks Arch Surg 2000; 385:261– 264. 18. Jaffe V, Young AE. Strap muscles in thyroid surgery: to cut or not to cut? Ann R Coll Surg Engl 1993; 75(2):118. 19. Hong KH, Kim YK. Phonatory characteristics of patients undergoing thyroidectomy without laryngeal nerve injury. Otolaryngol Head Neck Surg 1997; 117:399–404. 20. Gray SW, Skandalakis JE, Akin JT Jr. Embryological considerations of thyroid surgery: developmental anatomy of the thyroid, parathyroids, and the recurrent laryngeal nerve. Am Surgeon 1976; 42(9):621–628. 21. Cernea CR, Ferraz AR, Nishio S, Dutra A Jr, Hojaij FC, dos Santos LR. Surgical anatomy of the external branch of the superior laryngeal nerve. Head Neck 1992; 14:380–383. 22. Teitelbaum BJ, Wenig BL. Superior laryngeal nerve injury from thyroid surgery. Head Neck 1995; 17:36–40. 23. Sun SQ, Chang RW. The superior laryngeal nerve loop and its surgical implications. Surg Radiol Anat 1991; 13:175–180. 24. Moreau S, Goullet de Rugy M, Babin E, Salame E, Delmas P, Valdazo A. The recurrent laryngeal nerve: related vascular anatomy. Laryngoscope 1998; 108:1351–1353. 25. Sato I, Shimada K. Arborization of the inferior laryngeal nerve and internal nerve on the posterior surface of the larynx. Clin Anat 1995; 8:379–387. 26. Sasou S, Nakamura S, Kurihara H. Suspensory ligament of Berry: its relationship to recurrent laryngeal nerve and anatomic examination of 24 autopsies. Head Neck 1998; 20:695–698. 27. Leow CK, Webb AJ. The lateral thyroid ligament of Berry. Int Surg 1998; 83:75–78.

4 Thyroid-Stimulating Hormone Receptor YUJI NAGAYAMA Nagasaki University School of Medicine, Nagasaki, Japan

Thyroid stimulating hormone (TSH; thyrotropin) is the primary factor for regulating both differentiated function and growth of thyroid follicular epithelial cells (1). The action of TSH is initiated by its binding to TSH receptor (TSHR) on the basolateral site of the thyroid cell plasma membrane, which transduces signals through Gs-cAMP and, to a lesser extent, Gq-phospholipase C cascades. In pathological terms, TSHR involves thyroid autoimmunity and oncogenesis. Thus, TSHR, as well as thyroid peroxidase (TPO) and thyroglobulin (TG), is a target autoantigen in human autoimmune thyroid diseases such as Graves’ disease and Hashimoto’s thyroiditis. Autoantibodies against TSHR stimulate thyroid cells (stimulatory-type autoantibody) or block TSH action (blocking-type autoantibody) (2). Ectopic expression of TSHR may be involved in extrathyroidal manifestations of Graves’ disease such as ophthalmopathy and pretibial myxedema (3). Furthermore, gain- and loss-of-function mutations of the receptor have been found in hyperfunctioning adenoma/congenital nonautoimmune hyperthyroidism and congenital hypothyroidism, respectively (4,5). The presence of TSHR was first demonstrated in 1966 and its cDNA was cloned in late 1989/early 1990 (1,6).

I.

PRIMARY STRUCTURE OF TSHR

The full length of human (h) TSHR cDNA is approximately 4 kilobases (kb) in length and has a single open reading frame of 2292 base pairs, which encodes a protein of 743 amino acids (aa) (excluding a 21 aa signal peptide) with a calculated molecular mass of

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Figure 1 Schematic representation of TSHR. Holoreceptor (left) and two-subunit receptor (right) are shown.

84.5 kilodalton (kDa). It was anticipated before molecular cloning that TSHR would be structurally closely related to other glycoprotein hormone receptors (lutropin receptor [LHR] and follitropin receptor [FSHR]) and would belong to the G-protein-coupled receptor (GPCR) superfamily. The homology search indeed revealed that TSHR together with LHR and FSHR constitute a subgroup in the GPCR superfamily. Thus, the amino (N)terminal half of TSHR (397 aa, 45.2 kDa) corresponds to the large extracellular domain (ectodomain), a unique feature of the glycoprotein hormone receptor subfamily. The carboxyl (C)-terminal half (346 aa) is made up of transmembrane/cytoplasmic regions, including seven transmembrane segments, three extra- and intracellular loops, and a cytoplasmic tail, which is a characteristic of the GPCR superfamily (Fig. 1). The predicted aa sequence of TSHR shares very high homology among different species (85–90%). TSHR ectodomain is 35–45% homologous to those of LHR and FSHR and the transmembrane/cytoplasmic regions share 70–75% homology with other members of the GPCR superfamily. The middle region of TSHR ectodomain (aa 58–277) comprises nine leucine-rich repeats (LRRs) with a consensus sequence of x(Leu)xx(Thr)xx (Leu)(Thr)x(Leu)(Pro)xx(Ala)(Phe)xx(Leu)xx(Leu)xxx(Leu) (where x is any aa) and is

Thyroid-Stimulating Hormone Receptor

21

relatively homologous (⬃50%) to LHR and FSHR. LRRs are reported to play a significant role in protein–protein interaction, presumably for TSH binding in case of TSHR (see below). The N- and C-terminal extreme ends of the ectodomain are less conserved and contain two unique insertions (aa 38–45 and 317–366) compared to other glycoprotein hormone receptors. There are 13 cysteines in the extracellular region of TSHR (11 in the ectodomain and two in the extracellular loops); cysteines are clustered in N- and C-terminal extreme ends of the receptor ectodomain. There are also six potential Asn-linked glycosylation sites ([Asn]x[Ser/Thr], where x is any aa except Pro). II. TSHR STRUCTURE AND FUNCTION A. Protein Expression The expression of functional, conformationally intact full-length TSHR is so far limited to eukaryotic mammalian cells, including Chinese hamster ovary (CHO) cells, COS cells, 293HEK cells, SP2/0 myeloma cells, and others (7). Prokaryotic bacterial cells, eukaryotic insect cells, and in vitro transcription/translation are not adequate for this purpose, presumably because of lack of disulfide formation, glycosylation, and/or correct protein folding in these systems. The truncated form of the entire ectodomain of recombinant TSHR anchored to cell membrane through either a hydrophobic transmembrane segment, the CD8 transmembrane region, or a glycosylphosphatidylinositol tag, is reported to be expressed as a functional membrane protein (7). Furthermore, the recombinant truncated TSHR ectodomain, similar to TSHR A subunit (see below) rather than the whole ectodomain, can be produced as a soluble, secreted protein, which is highly potent in neutralizing TSHR autoantibodies, although it is unable to bind TSH (7). These recombinant proteins may be valuable for future analysis of TSHR structure and function. B.

Post-Translational Modifications

Like many other membranous and secreted proteins, TSHR protein undergoes a series of post-translational processing events in the endoplasmic reticulum (ER) and the Golgi apparatus, many of which are crucial for cell surface expression of functional TSHR. These modifications include disulfide-bonding, protein-folding, glycosylation, palmitoylation, proteolytic cleavage, and others. 1. Disulfide Bonding and Protein Folding Thirteen cysteines in the extracellular region of the receptor likely form six disulfide bonds with one orphan cysteine. Two cysteines in the extracellular loops (aa 494 and 569) likely bond with each other. There are three clusters of cysteines in the ectodomain; aa 24, 29, 31, and 41 at the N-terminus of the ectodomain; aa 283, 284, and 301 at the end of A subunit (see below); and aa 390, 398, and 408 at the N-terminus of B subunit. Mutagenesis studies demonstrate that 9 of 13 (aa 41, 283, 284, 301, 390, 398, 408, 494, and 569) reduce or abolish TSH binding (7). Although at present it is unclear which cysteines pair with each other to form disulfide bonds, there must be some disulfide bonding between A and B subunits, presumably between the second and third clusters (7). No doubt that these disulfide bonds significantly contribute to the very complex nature of TSHR ectodomain structure.

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In the deduced three-dimensional structural model of TSHR ectodomain–TSH complex estimated from crystallization and x-ray diffraction analysis of ribonuclease inhibitor, another LRR-containing protein, the LRRs of TSHR appear nonglobular and horseshoeshaped, and its concave surface likely interacts with TSH. Binding area appears more extensive than standard protein–protein interaction (8) (Fig. 1). 2. Asn-Linked Glycosylation TSHR is a glycoprotein with Asn-linked carbohydrates. TSHR holoreceptor can be detected as a ⬃100 and 120 kDa doublet in CHO cells in Western blotting and immunoprecipitation studies. The ⬃100 kDa protein is a precursor with high-mannose-type carbohydrates located in the ER and does not bind TSH. The ⬃120 kDa protein is a mature receptor with complex-type carbohydrates, expressed on the cell surface and is capable of binding to TSH (7,9). TSHR A subunit, which is mainly produced on the cell surface (see below), also has complex-type carbohydrates; ⬃40% of its molecular mass is carbohydrates. These findings are in agreement with the general concept for the processing of glycosylation, that is a dolichol pyrophosphate precursor is first attached to Asn residue of the consensus sequence for Asn-linked glycosylation site in the ER. This is processed to high-mannose-type carbohydrates in the ER and then to a complex type in the Golgi to give rise to structurally and functionally mature glycoprotein (10). A recent study with CHO-Lec cells shows that the addition of Asn-linked carbohydrates to TSHR in the ER is indispensable for completion of protein folding. Processing of high-mannose-type carbohydrates to a complex type plays a role in intracellular trafficking and cell surface expression of the receptor. Of interest, TSHR with high-mannosetype carbohydrates whose folding is accomplished in the ER is able to bind to TSH, but needs to be processed in the Golgi to be expressed on the cell surface (11), suggesting that complex-type carbohydrates are not necessary for TSH binding. Furthermore, the carbohydrates on TSHR may not be part of the TSH binding site and may not be necessary to maintain the correct folding once TSHR folds correctly, because deglycosylation of native TSHR is reported not to alter the receptor function (12). Of six potential Asn-linked glycosylation sites, two sites (aa 77 and 113) were originally reported to be critical for cell surface expression of the functional TSHR. However, a recent study clearly demonstrates that any single glycosylation site has no effect on receptor function and expression (13). The data indicate that at least four glycosylation sites are necessary for cell surface expression of the functional receptor. Indeed all six potential Asn-linked glycosylation sites appear to be actually glycosylated. 3. Palmitoylation As for many members of the G protein-coupled receptor superfamily, TSHR has a cysteine residue in the membrane proximal region of the C-terminal cytoplasmic tail (Cys at aa 699). Palmitic acid is shown to be covalently attached to this by thioesterification, presumably forming the fourth cytoplasmic loop (Fig. 1). The palmitoylation on this residue plays a role in controlling the rate of intracellular trafficking and cell surface expression of TSHR (14). 4. Subunit Formation by Intramolecular Cleavage Even before molecular cloning, TSHR had been demonstrated to undergo intramolecular cleavage into two subunits: TSH-binding “A subunit” and membrane-spanning “B subunit” (2). This was confirmed by eukaryotic cells expressing recombinant TSHR (6,7).


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Two types of mechanisms for cleavage are proposed. The first model proposed by de Bernard et al. (15) is that the primary cleavage site is near aa 300–320, and several additional cleavage (or degradation) sites occur at the N-terminus of the B subunit up to aa ⬃370. The second is from Rapoport and his associates (7), whose original thesis involved two cleavage sites (upstream site 1 is between aa 305 and 316; downstream site 2 is around aa 370), resulting in the release of a small peptide called “C peptide.” However, their recent study (16) indicates that the cleavage at upstream site 1 appears to be followed by rapid disintegration of the C-peptide region that stops downstream site 2. Degradation of the N-terminus of the B subunit then reaccelerates to the vicinity of the plasma membrane. Continued degradation would lead to A subunit shedding (see below). In either case, 50 aa insertion can be removed from the subunit structure. The cleavage does not involve a specific amino acid motif and appears to be influenced by tertiary structure near the cleavage sites (for example, 50 aa insertion for upstream site 1) (17). The enzyme involved in and functional significance of the cleavage remains to be determined. There is evidence to suggest that TSHR on the cell surface sheds A subunit into the circulation (7), following cleavage and reduction by protein disulfide isomerase (15), or disintegration of N-terminus of B subunit (16). The in vivo pathophysiological significance of TSHR ectodomain shedding is at present unclear, although A subunit is reportedly detectable in human sera (7). C.

Ligand Binding Sites

The binding sites for TSH and autoantibodies have been extensively studied with mutagenesis with homologous and nonhomologous substitutions and synthetic peptides. Unfortunately, many data are unconvincing and there still exist substantial amounts of controversy. For example, 200–300 aa have so far been reported to be ligand binding sites (7). Relatively reliable data include the following two findings. First, the binding sites for TSH and autoantibodies are situated in the ectodomain of the receptor and span the entire ectodomain; that is, the sites are very conformational and consist of discontinuous aa sequences (6). These data are consistent with the hypothetical TSH–TSHR complex model mentioned above, although the contribution of the extracellular loops cannot be completely excluded. The second is that the binding sites for TSH and autoantibodies appear to overlap with, but may not be identical to, each other. Thus, stimulating and blocking autoantibody binding seems to involve the N- and C-termini of the TSHR ectodomain, respectively (6,7). The middle region of the ectodomain, particularly aa 201–211 and 222–230, participates in TSH binding (6–8). III. STRUCTURE AND EXPRESSION OF TSHR GENE The human TSHR gene is located on chromosome 14q31 and consists of 10 exons spanning over 60 kb. Exons 1–9 encode the ectodomain and exon 10 encodes the transmembrane/cytoplasmic regions. LRRs 1–7 correspond to exons 2–8, and LRRs 8 and 9 to exon 9. Therefore, it is suggested that exon 10 encodes the prototype GPCR to which nine exons were evolutionarily added to shape the very complex form of TSHR ectodomain. TSHR mRNAs in human thyroid tissue include major transcripts of 4.6 and 3.9 kb in length and minor ones of 1.8 and 1.2 kb (1). The former is likely the full-length receptor, whereas the latter is identified by molecular cloning as a truncated protein (6). The extrathyroidal expression of TSHR is of interest because of its possible involve-

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ment in the pathogenesis of extrathyroidal manifestations of autoimmune thyroid disease such as Graves’ ophthalmopathy and pretibial myxedema. Detection of TSHR transcripts or protein by Northern blot or immunohistochemical methods, not by reverse transcriptionpolymerase chain reaction (RT-PCR), which may represent illegitimate transcription, has so far been reported in fibroblasts/adipose tissues of not only retro-orbital origin but also abdominal and mammary origin, thymus, and cardiac muscle (3,7).

IV.

AUTOIMMUNITY

A.

Autoantibodies

TSHR autoantibodies have been categorized into two types: one is the stimulatory type (thyroid-stimulating immunoglobulin [TSI] or antibody [TSAb]), which binds to and stimulates TSHR; and the other is the blocking type, which inhibits TSH binding and/or TSHmediated cAMP synthesis. To detect these autoantibodies, two types of assays have been developed; one is a bioassay for TSI, and the other is a competition of antibodies for radiolabeled TSH binding to TSHR (TSH-binding-inhibiting immunoglobulin [TBII] or antibody [TBIAb]). The TSI bioassay detects stimulating-type antibody, whereas the TBII assay cannot differentiate between stimulating and blocking antibodies. However, because of its simplicity, the TBII assay is now being used as a method for TSHR antibody measurement in most clinical laboratories. For the TSI assay, although human, porcine, or rat thyroid cells have been long utilized, molecular cloning of hTSHR cDNA made it possible to use eukaryotic mammalian cells stably expressing recombinant hTSHR, whose sensitivity is equivalent or superior to thyroid cells (18). Furthermore, a new chemiluminescent TSI assay has been developed in which cAMP response to TSH and TSI stimulation can be detected by measuring light output in a luminometer in a CHO cell line stably transfected with both TSHR cDNA and cAMP-responsive firefly luciferase gene. This new method can eliminate cAMP measurement by radioimmunoassay (RIA), but awaits further studies to confirm its clinical value. For the TBII assay, a crude detergent extract of porcine thyroid membrane and highly potent, affinity-purified TSH has long been available as a commercial kit (2). TBII assays using recombinant hTSHR protein have also recently been reported (19,20), one of which is now commercially available (19). Their specificity and sensitivity are reportedly superior to the conventional assay. In both cases, use of hTSHR is an advantage, although the results obtained with hTSHR are generally closely correlated with those with other species of the receptor, and the poor correlation between TSI and TBII in Graves’ disease is still observed in assays with hTSHR (18). New assays by which TSHR autoantibodies can be detected by direct binding to TSHR have also been reported with TSHR fused to firefly luciferase (21), TSHR fused to the biotin carboxyl carrier subunit of E. coli (22), purified full-length TSHR (23), and purified truncated TSHR (24). These assays can detect many types of antibodies including TSI, TBII, and “neutral” antibody that show neither stimulatory nor inhibitory activities. A relatively close correlation between the direct binding assay and TBII is reported (22– 24). Some chimeric TSH/LHRs are reported to be useful to predict patients’ response to antithyroid drug treatment (25).


B.

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Animal Models

Unlike TG and TPO, the traditional immunological approach, that is, immunization of the animal with soluble TSHR ectodomain in adjuvant, has not worked well to induce TSHR-mediated thyroid autoimmunity. Furthermore, transfer of Graves’ pathology into mice with severe combined immunodeficiency proved inefficient (26). Recently, however, successful induction of experimental hyperthyroidism has been reported by several laboratories (26). First, immunization of fibroblasts stably expressing TSHR and class II antigen induced TSI, hyperthyroidism, and diffuse goiter in a fraction of the immunized mice (27). However, the hyperplastic glands lack lymphocyte infiltration, which is a characteristic of autoimmune thyroid disease. Of interest, Th2 (pertussis toxin) and Th1 complete Freund adjuvant (CFA) adjuvants increased the incidence of hyperthyroidism up to ⬃50% and delayed the disease onset, respectively (28). Second, DNA immunization of outbred mice (29), not inbred mice, proved valuable for inducing TSHR antibodies in almost all the immunized mice and hyperthyroidism and goiter with lymphocyte infiltration in a fraction of the immunized mice. The infiltrates are CD4⫹ T lymphocytes and B cells, which are characteristic of Th2 humoral immune response. Furthermore, extraocular lesions such as edema, fibrosis, and cellular infiltrate, with resemblance to Graves’ ophthalmopathy, were also seen in the extraocular muscles. Of interest, similar eye signs are observed in inbred mice immunized by passive transfer of T cells from the mice that received DNA vaccination (30). More recently, generation of hyperthyroidism at the higher incidence in a mouse strain by immunization with a syngeneic B lymphoma cell line stably expressing TSHR has been reported (31). A difference in the incidence may be due to higher expression of costimulatory molecules on B cells than fibroblasts, which is crucial for T-cell stimulation.

V. NATURALLY OCCURRING MUTATIONS It is logical to assume that gain-of-function mutations in any step of the Gs-cAMP cascade can be oncogenic in tissues in which cAMP is a growth factor. This was first verified in growth hormone–secreting pituitary adenomas, followed by other functional endocrine tumors including hyperfunctional thyroid adenomas. The similar constitutively activating mutations were later found in nonautoimmune congenital hyperthyroidism, toxic multinodular goiters, and some thyroid carcinomas (4,5). All the mutations except aa 281 are localized in the transmembrane/cytoplasmic regions, particularly in the third cytoplasmic loop and the sixth transmembrane segment. TSHR is known to display significant constitutive activity even in the absence of agonist. Identification of a constitutively activating mutation in the receptor ectodomain (aa 281) may suggest that the unliganded ectodomain of wt-TSHR appears to constrain the receptor activity. There appears to be a geographical difference in the incidence of toxic adenomas and multinodular goiters. It is also a reasonable assumption that loss-of-function mutations in any step of the Gs-cAMP cascade can result in hypothyroidism associated with TSH unresponsiveness. Thus, congenital hypothyroidism associated with resistance to TSH was found in homozygotes or compound heterozygotes (different mutations in each allele) with loss-of-function mutations of TSHR (4,5). The mutations can be seen in any region of the receptor. A unique TSHR mutation (K183R) is also identified in a familial gestational hyperthyroidism, which is reported to be more sensitive to human choriogonadotropin than the wt-receptor (32).

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The TSHR mutation data base is now available on the World Wide Web at http:// www.uni-leipzig.de/⬃innere/TSH/frame_en.htm.

REFERENCES 1. Vassart G, Dumont JE. The thyrotropin receptor and the regulation of thyrocyte function and growth. Endocr Rev 1992; 13:596–611. 2. Rees Smith B, McLachlan SM, Furmaniak J. Autoantibodies to the thyrotropin receptor. Endocr Rev 1988; 9:106–121. 3. Rapoport B, Alsabeh R, Aftergood D, McLachlan SM. Elephantiasic pretibial myxedema: insight into and a hypothesis regarding the pathogenesis of the extrathyroidal manifestations of Graves’ disease. Thyroid 2000; 10:685–692. 4. Van Sande J, Parma J, Tonacchera M, Swillens S, Dumont J, Vassart G. Somatic and germline mutations of the TSH receptor gene in thyroid diseases. J Clin Endocrinol Metab 1995; 80: 2577–2585. 5. Russo D, Arturi F, Chiefari E, Filetti S. Molecular insights into TSH receptor abnormality and thyroid disease. J Endocrinol Invest 1997; 20:36–47. 6. Nagayama Y, Rapoport B. The thyrotropin receptor 25 years after its discovery: new insight after its molecular cloning. Mol Endocrinol 1992; 6:145–156. 7. Rapoport B, Chazenbalk GD, Jaume JC, McLachlan SM. The thyrotropin (TSH) receptor: interaction with TSH and autoantibodies. Endocrinol Rev 1998; 19:673–716. 8. Kajava AV, Vassart G, Wodak SJ. Modeling of the three-dimensional structure of proteins with the typical leucine-rich repeats. Structure 1995; 3:867–877. 9. Oda Y, Sanders J, Roberts S, Maruyama M, Kiddie A, Furmaniak J, Smith B. Analysis of carbohydrate residues on recombinant human thyrotropin receptor. J Clin Endocrinol Metab 1999; 84:2119–2125. 10. Kornfeld R, Kornfeld S. Assembly of asparagine-linked oligosaccharides. Annu Rev Biochem 1985; 54:631–664. 11. Nagayama Y, Namba H, Yokoyama N, Yamashita S, Niwa M. Role of asparagine-linked oligosaccharides in protein folding, membrane targeting, and thyrotropin and autoantibody binding of human thyrotropin receptor. J Biol Chem 1998; 273:33423–33428. 12. Atger M, Misrahi M, Young J, Jolivet A, Orgiazzi J, Schaison G, Milgrom E. Autoantibodies interacting with purified native thyrotropin receptor. Eur J Biochem 1999; 265:1022–1031. 13. Nagayama Y, Nishihara E, Namba H, Yamashita S, Niwa M. Identification of the sites of asparagine-linked glycosylation on the human thyrotropin receptor and studies on their role in the receptor function and expression. J Pharmacol Exp Ther 2000; 295:404–409. 14. Tanaka K, Nagayama Y, Nishihara E, Namba H, Yamashita S, Niwa M. Palmitoylation of the human thyrotropin receptor. Slower intracellular trafficking of the palmitoylation-defective mutant. Endocrinology 1998; 139:803–806. 15. de Bernard S, Misrahi M, Huet JC, Beau I, Desroches A, Loosfelt H, Pichon C, Pernollet JC, Milgrom E. Sequential cleavage and excision of a segment of the thyrotropin receptor ectodomain. J Biol Chem 1999; 274:101–107. 16. Tanaka K, Chazenbalk GD, McLachlan SM, Rapoport B. Subunit structure of thyrotropin receptors expressed on the cell surface. J Biol Chem 1999; 274:33979–33984. 17. Tanaka K, Chazenbalk GD, McLachlan SM, Rapoport B. Thyrotropin receptor cleavage at site 1 does not involve a specific amino acid motif but instead depends on the presence of the unique, 50 amino acid insertion. J Biol Chem 1998; 273:1959–1963. 18. Gupta MK. Thyrotropin-receptor antibodies in thyroid diseases: advances in detection techniques and clinical applications. Clin Chim Acta 2000; 293:1–29. 19. Costagliola S, Morgenthaler NG, Hoermann R, Badenhoop K, Struck J, Freitag D, Poertl S, Weglohner W, Hollidt JM, Quadbeck B, Dumont JE, Schumm-Draeger PM, Bergmann A,


20.

21.

22.

23.

24. 25.

26. 27.

28.

29.

30. 31. 32.

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Mann K, Vassart G, Usadel KH. Second generation assay for thyrotropin receptor antibodies has superior diagnostic sensitivity for Graves’ disease. J Clin Endocrinol Metab 1999; 84:90– 97. Kakinuma A, Chazenbalk GD, Jaume JC, Rapoport B, McLachlan SM. The human thyrotropin (TSH) receptor in a TSH binding inhibition assay for TSH receptor autoantibodies. J Clin Endocrinol Metab 1997; 82:2129–2134. Minich WB, Loos U. Detection of functionally different types of pathological autoantibodies against thyrotropin receptor in Graves’ patients sera by luminescent immunoprecipitation analysis. Exp Clin Endocrinol Diabetes 2000; 108:110–119. Minich WB, Weymayer JD, Loos U. Immunoprecipitation analysis of pathological autoantibodies in Graves’ patients’ sera using biotinated human thyrotropin receptor labeled with 125Ineutravidiny. Exp Clin Endocrinol Diabetes 1999; 107:555–560. Sanders J, Oda Y, Roberts S, Kiddie A, Richards T, Bolton J, Mcgrath V, Walters S, Jaskolski D, Furmaniak J, Smith B. The interaction of TSH receptor autoantibodies with 125Ilabelled TSH receptor. J Clin Endocrinol Metab 1999; 84:3797–3802. Chazenbalk GD, Pichurin P, McLachlan SM, Rapoport B. A direct binding assay for thyrotropin receptor autoantibodies. Thyroid 1999; 9:1057–1061. Kim WB, Cho BY, Park HY, Lee HK, Kohn LD, Tahara K, Koh CS. Epitopes for thyroidstimulating antibodies in Graves’ sera: a possible link of heterogeneity to differences in response to antithyroid drug treatment. J Clin Endocrinol Metab 1996; 81:1758–1767. Ludgate M. Animal models of Graves’ disease. Eur J Endocrinol 2000; 142:1–8. Shimojo N, Kohno Y, Yamaguchi K, Kikuoka S, Hoshioka A, Niimi H, Hirai A, Tamura Y, Saito Y, Kohn LD, Tahara K. Induction of Graves-like disease in mice by immunization with fibroblasts transfected with the thyrotropin receptor and a class II molecule. Proc Natl Acad Sci USA 1996; 93:11074–11079. Kita M, Ahmad L, Marians RC, Vlase H, Unger P, Graves PN, Davies TF. Regulation and transfer of a murine model of thyrotropin receptor antibody mediated Graves’ disease. Endocrinology 1999; 140:1392–1398. Costagliola S, Many MC, Dehef JF, Pohlenz J, Refetoff S, Vassart G. Genetic immunization of outbred mice with thyrotropin receptor cDNA provides a model of Graves’ disease. J Clin Invest 2000; 105:803–811. Many MC, Costagliola S, Detrait M, Denef JF, Vassart G, Ludgate M. Development of an animal model of autoimmune thyroid eye disease. J Immunol 1999; 162:4966–4974. Kaithamana S, Fan J, Osuga Y, Liang SG, Prabhakar BS. Induction of experimental autoimmune Graves’ disease in BALB/c mice. J Immunol 1999; 163:5157–5164. Rodien P, Bremont C, Raffin Sanson ML, Parma J, Van Sande J, Costagliola S, Luton J-P, Vassart G, Duprez L. Familial gestational hyperthyroidism caused by a mutant thyrotropin receptor hypersensitive to human chorionic gonadotropin. N Engl J Med 1998; 339:1823– 1826.

5 Laboratory Evaluation of Graves’ Disease PHILLIPPA J. MIRANDA and DIANA McNEILL Duke University Medical Center, Durham, North Carolina, U.S.A.

I.

INTRODUCTION

Graves’ disease is a form of hyperthyroidism that occurs when circulating antibodies that mimic thyroid-stimulating hormone (TSH) stimulate the thyroid gland, causing a hyperthyroid state. In 1956, Adams and Purves reported on a patient with Graves’ disease whose blood contained a factor that caused stimulation of animal thyroid (1). This factor’s effect was much longer than TSH and was called long-acting thyroid stimulator (LATS). Kriss subsequently demonstrated in 1964 that this compound had the structure of an IgG immunoglobulin and could be neutralized by thyroid tissue (2). These findings gave rise to the concept that a circulating antibody mimicked TSH and caused Graves’ disease. This antibody is directed against the TSH receptor on the thyroid follicular cell and can now be measured. The antibody is referred to as thyroid-stimulating immunoglobulin (TSI) or TSH receptor antibody (TRAb). Although the demonstration of an antibody as the causative agent in Graves’ disease was important in our understanding of thyroid disease, the laboratory evaluation of Graves’ disease does not rely on this test. The laboratory evaluation of Graves’ disease should answer three questions instead: 1. Is the patient biochemically hyperthyroid? 2. What is the uptake of iodine by the thyroid gland? 3. Are stimulating thyroid antibodies present? The laboratory tests used to answer these questions are summarized in Table 1.

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Table 1 Overview of Thyroid Function Tests Biochemically hyperthyroid? In vitro tests TSH Free T4 Total T4 T3 resin uptake Free thyroxine index Free T3 Total T3

Uptake of iodine?

Antibodies present?

In vivo tests Radioactive iodine uptake

Serological tests TSI

TBII

TRAb

II. IS THE PATIENT BIOCHEMICALLY HYPERTHYROID? The first step in the laboratory evaluation of Graves’ disease is to determine if the patient is hyperthyroid by using basic laboratory tests. A TSH level and a free thyroxine level (free T4) or equivalent (free thyroxine index, FTI) must be obtained. A suppressed TSH level is consistent with the diagnosis of hyperthyroidism, in the presence of normal pituitary function. If the TSH is suppressed but the T4 is normal, a tri-iodothyronine (T3) level should be obtained to evaluate for T3 toxicosis, which is more common in early Graves’ disease or recurrence of hyperthyroidism. Initial evaluation should start with a TSH measurement and proceed to a free T4 and free T3 if the TSH value is abnormal (3). A.

TSH

A low or suppressed TSH value is seen in Graves’ disease and other causes of hyperthyroidism. Measurements of TSH have improved greatly since Odell first measured TSH in 1965 (4). TSH was initially measured using a radioimmunoassay (RIA) technique, which used a single antibody and competitive binding. Although this method was adequate for measuring high levels of TSH seen in hypothyroidism, the lower limit of detection was 1.0 mU/L, making the determination of hyperthyroidism impossible. This type of TSH assay, referred to as a first-generation TSH assay, was capable only of differentiating hypothyroid from euthyroid patients, but was not useful in differentiating euthyroid from hyperthyroid patients. In the mid-1980s, second-generation TSH assays were developed using an immunometric assay (IMA) technique, with either a monoclonal or polyclonal antibody (5,6). In this method, two anti-TSH antibodies are used to create a sandwich configuration, thus improving the sensitivity of the assay (Fig. 1). One antibody is attached to a solid-phase substrate, such as a test tube, plastic beads, or ferromagnetic particles. The second antibody is labeled with a radioisotope, enzyme, fluorescent marker, or chemiluminescent molecule. Since two sites on the TSH molecule must be recognized, the sensitivity is greatly improved. Immunometric assays are noncompetitive, with the label being directly proportional to the TSH concentration. The increased sensitivity and specificity of this method allow measurement of TSH down to 0.1 mU/L. These TSH assays are capable of differentiating euthyroid from hyperthyroid patients and are termed “sensitive TSH” assays (7– 12). These assays are known by a variety of other names, depending on the label found on the second antibody (Table 2).

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31

Figure 1 Second-generation, so-called sensitive TSH assay, using two antibodies: one antibody attached to solid substrate and one antibody with a label attached. The TSH molecule is sandwiched between the two antibodies.

Finally, in 1990, a third-generation immunochemiluminometric assay (ICMA) was reported with improved analytical and functional sensitivity and a lower limit of detection of ⬍0.01 mU/L (13). This type of assay can differentiate mild TSH suppression due to nonthyroidal illness (⬎0.01 mU/L) from profound TSH suppression (⬍0.01 mU/L) due to hyperthyroidism and is termed ultrasensitive TSH assay. A variety of third-generation TSH assays are now commercially available (14). Other third-generation TSH assay techniques include two-site chemiluminescent immunoassays and time-resolved immunofluorometric assays (TR-IFMA) (15,16). In summary, the lower limits of detection are 1.0 mU/L for first-generation TSH assays, 0.1 mU/L for second-generation TSH assays, and 0.01 mU/L for third-generation TSH assays (Table 3). In hyperthyroidism due to Graves’ disease, the TSH is usually less than 0.1 mU/L. Despite these significant improvements in TSH measurements, there are several situations in which TSH does not reflect the patient’s thyroid status. Hospitalized patients frequently have abnormal TSH levels without thyroid disease, because of nonthyroidal illness or use of medications (Table 4) (17–21). TSH is also unreliable with recent changes in thyroid medications before the patient reaches steady state, which can take 6– 8 weeks. A subnormal TSH level can also be seen in the first trimester of pregnancy and in patients with acute psychiatric illness (22). Finally, the unusual situations of central hypothyroidism, TSH-secreting pituitary tumors, and central resistance to thyroid hormone result in TSH levels that do not correspond to the clinical status of the patient.

Table 2

Second-Generation TSH Assays

Assay name

Label type on second antibody

Immunoradiometric Immunofluorometric Immunoenzymometric

Radioactive Fluorophor Enzyme

Immunochemiluminometric

Chemiluminescent

Example 125

I Rhodamine Peroxidase Alkaline phosphatase Luminol Dioxetanes Acrydinium esters

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Table 3 TSH Assays Generation of TSH assay First Second Third

B.

Technique Radioimmunoassay Immunometric assay Immunochemiluminometric assay

Lower limits of normal

Sensitivity

1.0 mU/L 0.1 mU/L 0.01 mU/L

⫹ ⫹⫹ ⫹⫹⫹

Thyroid Hormone Measurements

In addition to TSH, measurements of the thyroid hormones T4 and T3 should be obtained. These hormones are found circulating in the bound and unbound states. Thyroid hormones are bound to serum proteins, including albumin, prealbumin, and thyroid-binding globulin (TBG). The total thyroid hormone levels include both the bound and unbound (free) fractions. Both free and total thyroid hormone levels will be elevated in patients with Graves’ disease and other causes of hyperthyroidism. C.

Free Thyroxine

Free T4 is the portion of thyroxine not bound to serum proteins and reflects tissue hormone levels and the patient’s metabolic status. By measuring free T4 directly, the variations in protein serum and thyroxine-binding globulin levels do not affect the measured hormone level. In order for measurements of free T4 to be valid, the equilibrium between free and bound hormone must be preserved (23). Free T4 can be measured by four methods: direct immunoassays (DIA), “indirect” tracer equilibrium dialysis, “direct” equilibrium dialysis with sensitive radioimmunoassay of dialysate, or ultrafiltration. Direct equilibrium dialysis, available in larger clinical laboratories, is considered to be the reference method for measuring free hormone levels, while ultrafiltration of undiluted sera is a research method (24–26). Direct immunoassays are employed when free T4 is measured in most clinical laboratories, due to ease and cost considerations, despite potential bias due to binding of labeled tracer to the patient’s serum proteins (10,23,25,27). DIA can be “one-step” (analogue) or “two-step” (back titration), and over 20 kits are commercially available (28–30). In the one-step method, labeled Table 4 Drugs That Affect TSH Drugs that increase TSH Lithium Iodine and iodine-containing compounds Dopamine antagonists Cimetidine Spironolactone Amphetamine Clomiphene

Drugs that decrease TSH Thyroxine and triiodothyronine Dopamine and dopaminergic agents Bromocriptine Apomorphine Alpha-noradrenergic blockers Serotonin antagonists Glucocorticoids Somatostatin Opiates Clofibrate


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tracer (hormone or hormone analogue) and solid-phase antibody are added to the patient’s serum at the same time. The patient’s free hormone and labeled tracer compete for sites on the solid phase antibody. In the two-step method, solid-phase antibody is added to the patient’s serum first. Then the patient’s serum is removed and labeled tracer is added, which binds to the remaining solid-phase antibody sites. Since the patient’s serum and labeled tracer do not mix directly, binding of tracer to serum proteins cannot occur. With both methods, the amount of labeled tracer bound to the solid-phase antibody indirectly indicates the free hormone level. Although there is conflict in the literature, two-step DIA methods seem to be more accurate and reliable (29,31). Although equilibrium dialysis and ultrafiltration are generally considered to be more accurate methods than DIA, Liewendahl et al. showed good correlation between free T4 measured by equilibrium dialysis and by DIA (32). In the setting of critical nonthyroidal illness, free T4 is often low when measured by two-step DIA. Equilibrium dialysis with undiluted serum or ultrafiltration may be better able to differentiate euthyroid from hypothyroidism in critically ill patients (33). In patients with familial dysalbuminemic hyperthyroxinemia, antithyroxine antibodies, or triiodothyronine antibodies, interference with free T4 assays can occur and give falsely high results (34). D. Total Thyroxine In 1965, measurement of total thyroxine (TT4) by thin-layer chromatography was reported by West (35). Although free (unbound) T4 is now the preferred test for assessing thyroid hormone production, measurements of TT4 are still frequently performed. Total T4 includes free thyroxine and thyroxine bound to proteins, including albumin, prealbumin, and TBG. The standard method for measuring TT4 is radioimmunoassay (36). Total T4 is usually increased in hyperthyroidism, including hyperthyroidism due to Graves’ disease. Other causes of elevated TT4 include increased TBG, increased binding of thyroxine to albumin or prealbumin, medications, pregnancy with hyperemesis gravidarum, endogenous antibodies to T4, peripheral resistance to thyroid hormone, and familial dysalbuminemic hyperthyroxinemia (37–39). Nonthyroidal illness can cause elevation or suppression of TT4. Although TT4 does not always reflect the metabolic status of the patient, TT4 in conjunction with the triiodothyronine resin uptake (T3RU) can be used to calculate the free thyroxine index (FTI), which does correlate with metabolic status. E.

Triiodothyronine Resin Uptake

The T3RU is an indirect measurement of the thyroid-binding globulin (Fig. 2). In this test, radiolabeled T3 is added to the patient’s serum, which contains T3, T4, and binding proteins. The radiolabeled T3, patient’s T3, and patient’s T4 bind to the binding proteins found in the patient’s serum. A portion of the radiolabeled T3 is not bound to the patient’s binding proteins. The unbound radiolabeled T3 is absorbed onto an ion exchange resin. The amount of radiolabeled T3 bound to the ion exchange resin (T3 resin uptake) can be measured. This value indirectly measures the amount of serum-binding proteins in the patient’s serum. When TBG is low, T3RU increases; when TBG is high, T3RU decreases. F. Free Thyroxine Index When a direct measurement of free T4 is not available, the TT4 and T3RU can be used to calculate an estimate of the free T4, which is called free thyroxine index (FTI). The

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Figure 2 T3 resin uptake test. (1) Patient’s serum with T4 bound to TBG. Labeled T3 is added. (2) Labeled T3 fills empty TBG. (3) Ion exchange resin is added. (4) Free labeled T3 binds to ion exchange resin. (5) Amount of labeled T3 bound to ion exchange resin is measured. If TBG levels are low, T3RU is high. If TBG levels are high, T3RU is low.

FTI reflects the free thyroxine level because the T3RU accounts for the changes in proteins to which T4 binds while circulating in the body. The FTI is obtained by multiplying the TT4 and T3RU. FTI ⫽ TT4 ⫻ (T3RU measured)/(T3RU normal) When extremes of TBG exist or nonthyroidal illness occurs, the FTI may not accurately reflect the actual free T4 (37). G.

Free Triiodothyronine

Free triiodothyronine (free T3) is the unbound portion of T3. Free T3 is usually measured when there is evidence of thyrotoxicosis (low TSH) with a normal thyroxine level. Measuring the free T3 directly is preferred, since the variations in protein binding and TBG levels do not affect the free hormone level. The reference method for measuring free T3 is equilibrium dialysis; however, two-step radioimmunoassays, labeled analog competitive immunoassays, labeled antibody immunoassays, and time-resolved fluoroimmunoassays are also available (16,29,30,40,41). As with free T4 assays, the measurement of free T3 by a two-step DIA has been shown to correlate well with results from equilibrium dialysis (40). Although a variety of thyroid hormone changes can be seen with nonthyroidal illness, a low free T3 due to decreased peripheral conversion of T4 to T3 is the most common (33,42).


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H. Total Triiodothyronine TT3, like TT4, is measured by radioimmunoassay. TT3 is a combination of free T3 and T3 bound to serum proteins. T3 binds to serum proteins such as TBG with less affinity than T4. The amount of metabolically active T3 is affected by binding to serum proteins and peripheral conversion of T4 to T3. Total or free T3 can be used to assess for T3 toxicosis in patients with undetectable TSH and normal T4. III. WHAT IS THE UPTAKE OF IODINE BY THE THYROID GLAND? Radioactive iodine scanning and uptake measurements are very helpful in differentiating Graves’ disease from other causes of hyperthyroidism. In a survey of members of the American Thyroid Association in 1990, 92.3% of respondents would obtain a radioiodine uptake as part of the initial evaluation of Graves’ disease (43). In this test, the patient swallows a capsule containing radioactive iodine, usually 3–5 µCi 131I or 123I, and the uptake of the radioactive iodine by the thyroid gland is measured at 24 h, using nuclear medicine imaging techniques. Measurements of radioiodine uptake can also be made at 3–6 h with comparable results (44). Iodine is the preferred isotope because it is both transported and organified by the thyroid follicular cell. 131I is effective whether the thyroid is in the chest or neck; however, technetium pertechnetate (99 mTc) and 123I are more effective when the thyroid is in the neck (45). The normal range of iodine uptake is 10– 30% and is inversely proportional to dietary iodine intake. A low-iodine diet may increase radioiodine uptake by the thyroid (46). Low uptake of radioactive iodine by the gland indicates thyroiditis or excessive thyroid hormone ingestion as the cause of hyperthyroidism. High uptake is caused by Graves’ disease, resulting in diffuse uptake; single toxic or hyperfunctioning nodule, with focal uptake; and toxic multinodular goiter, with diffuse or multiple focal areas of increased uptake. In addition to providing information about the cause of hyperthyroidism, the amount of uptake of iodine by the thyroid gland determines the dose of radioiodine needed for radioactive iodine (RAI) ablation therapy. IV.

ARE STIMULATING THYROID ANTIBODIES PRESENT?

Although the presence of antibodies may help to confirm the diagnosis of Graves’ disease, a measurement of thyroid-stimulating antibodies is not required in order to make the diagnosis of Graves’ disease. The nomenclature of thyroid-stimulating antibodies is confusing. The terms thyroid-stimulating immunoglobulin or antibody (TSI, TSAb); TSH-bindinginhibiting immunoglobulin or antibody (TBII, TBIA); and thyroid receptor antibody or TSH receptor antibody (TSHRAb) all refer to the same molecule, but measured with different techniques (47). The American Thyroid Association (ATA) recommends the use of the term TSH receptor autoantibody (TRAb), followed by a description of the assay used (48). TSI is present in 85% of patients with Graves’ disease; by measuring both TSI and TBII, 98% of patients with Graves’ disease will be detected. TSI is present in 92% of patients with hyperthyroid Graves’ disease, while TBII is present in 92% of patients with hyperthyroid Graves’ disease. By measuring both TSI and TBII, 99% of patients with hyperthyroid Graves’ disease will be detected (49). Other thyroid antibodies include antithyroid peroxidase antibody (TPOAb), also called antimicrosomal antibody (AMA), and antithyroglobulin antibody (TgAb). TPOAb

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is useful in the diagnosis of Hashimoto’s thyroiditis, postpartum thyroiditis, and polyglandular autoimmune disease. TgAb interferes with measurement of thyroglobulin, which is used as a tumor marker in patients with thyroid cancer. These antibodies are not useful in the evaluation of Graves’ disease (50). There are several methods for measuring TRAb, although no standardization exists (50). Current antibody assays do not use intact animals, but instead use thyroid cell membranes or thyroid slices to measure antibody activity. The TBII assay measures inhibition of binding of labeled TSH to its receptor by the antireceptor antibody. The TSI assay demonstrates an increase in thyroid function after attachment of the antibody to the TSH receptor and is dependent on generation of cAMP. Both of these tests are measuring the same antibody, TRAb, via different techniques (51). Some experts advocate the measurement of both TSI and TBII activity for accurate clinical correlation (52). A variety of new techniques have been developed to measure TRAb. A secondgeneration assay for TRAb, using a murine monoclonal antibody in conjunction with radioactive and nonradioactive coated tube technology, demonstrates inhibition of TSH binding to its receptor by sera of patients with Graves’ disease, with specificity of 99.6% and sensitivity of 98.8% (53). Several techniques use a CHO cell line with a luciferase reporter plasmid to demonstrate TSH receptor stimulation, caused by sera of Graves’ disease patients (49,54–56). Measurement of thyroid antibodies is not always necessary to make or confirm the diagnosis of Graves’ disease in routine cases. A positive result of TRAb testing does not prove that the patient is hyperthyroid or has Graves’ disease. TRAb usually continues to increase for several months after 131I therapy for Graves’ disease. TRAb usually declines with antithyroid drug therapy. A meta-analysis of 18 studies demonstrated that the absence of TRAb is protective against relapse of Graves’ disease after antithyroid drug therapy (57–59). There are several situations in which TRAb measurements are indicated. In a patient with ophthalmopathy who is clinically and biochemically euthyroid, high levels of TRAb favor a diagnosis of euthyroid Graves’ disease over orbital tumor (60). Kazuo et al. compared TBII and TSI in 62 patients with thyroid-associated ophthalmopathy and showed that TSI is a better marker for euthyroid ophthalmopathy than TBII (60). In patients with known Graves’ thyroid disease who are euthyroid, the titers of TSI and TBII correlate with the severity, but not the duration, of the eye disease (61). In a pregnant patient, high TRAb levels measured during weeks 28–30 predict fetal or neonatal Graves’ disease, regardless of the mother’s thyroid status (47,62). The presence of TRAb in a baby may confirm the diagnosis of transient neonatal hyperthyroidism due to transplacental passage of blocking TRAb (62). When RAI uptake cannot be performed, such as during pregnancy or recent iodine exposure, positive results of TRAb testing favor the diagnosis of Graves’ disease over other causes of hyperthyroidism.

REFERENCES 1. Adams DD, Purves HD. Abnormal responses in the assay of thyrotropin. Proc Univ Otago Med Sch 1956; 34:11–12. 2. Kriss JP, Pleshakov V, Chien JR. Isolation and identification of the long-acting thyroid stimulator and its relation to hyperthyroidism and circumscribed pretibial myxedema. J Clin Endocrinol Metab 1964; 24:1005–1028.


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3. Nordyke RA, Reppun TS, Madanay LD, Woods JC, Goldstein AP, Miyamoto LA. Alternative sequences of thyrotropin and free thyroxine assays for routine thyroid function testing: quality and cost. Arch Intern Med 1998; 158:266–272. 4. Odell WD, Wilber JF, Paul WE. Radioimmunoassay of thyrotropin in human serum. J Clin Endocrinol Metab 1965; 25:1179–1188. 5. Seth J, Kellett HA, Caldwell G, Sweeting VM, Beckett GJ, Gow SM, Toft AD. A sensitive immunoradiometric assay for serum thyroid stimulating hormone: a replacement for the thyrotropin releasing hormone test? Br Med J 1984; 289:1334–1336. 6. Caldwell G, Gow SM, Sweeting VM, Kellett HA, Beckett GJ, Seth J, Toft AD. A new strategy for thyroid function testing. Lancet 1985; 1117–1119. 7. Klee GG, Hay ID. Sensitive thyrotropin assays: analytic and clinical performance criteria. Mayo Clin Proc 1988; 63:1123–1132. 8. Hershman JM, Pekary AE, Smith VP, Hershman JD. Evaluation of five high-sensitivity American thyrotropin assays. Mayo Clin Proc 1988; 63:1133–1139. 9. Nicoloff JT, Spencer CA. Clinical review 12: the use and misuse of the sensitive thyrotropin assays. J Clin Endocrinol Metab 1990; 71:553–558. 10. Hay ID, Bayer MF, Kaplan MM, Klee GG, Larsen PR, Spencer CA. American Thyroid Association assessment of current free thyroid hormone and thyrotropin measurement and guidelines for future clinical assays. Clin Chem 1991; 37:2002–2008. 11. Spencer CA, Takeuchi M, Kazarosyan M. Current status and performance goals for serum thyrotropin (TSH) assays. Clin Chem 1996; 42:140–145. 12. Watts NB. Use of a sensitive thyrotropin assay for monitoring treatment with levothyroxine. Arch Intern Med 1989; 149:309–312. 13. Spencer CA, LoPresti JS, Patel A, Guttler RB, Eigen A, Shen D, Gray D, and Nicoloff JT. Applications of a new chemiluminometric thyrotropin assay to subnormal measurement. J Clin Endocrinol Metab 1990; 70:453–460. 14. Wilkinson E, Rae PWH, Thomson KJT, Toft AD, Spencer CA, Beckett GJ. Chemiluminescent third-generation assay (Amerlite TSH-30) of thyroid-stimulating hormone in serum or plasma assessed. Clin Chem 1993; 39:2167–2173. 15. Chen CK, Tsai KS. Clinical application of chemiluminescent immunoassay for thyroid stimulating hormone, free T4 and intact-parathyroid hormone. J Formos Med Assoc 1996; 95:197– 202. 16. Taimela E, Aalto M, Koskinen P, Irajala K. Clinical and laboratory studies of time-resolved fluorescence immunoassays of thyrotropin and free triiodothyronine. Clin Chem 1993; 39: 679–682. 17. Kaptein EM, Spencer CA, Kamiel MB, Nicoloff JT. Prolonged dopamine administration and thyroid hormone economy in normal and critically ill subjects. J Clin Endocrinol Metab 1980; 51:387–393. 18. Van den Berghe G, de Zegher F, Lauwers P. Dopamine and the sick euthyroid syndrome in critical illness. Clin Endocrinol 1994; 41:731–737. 19. Spencer CA, Eigen A, Shen D, Duda M, Qualis S, Weiss S, Nicoloff JT. Specificity of sensitive assays of thyrotropin (TSH) used to screen for thyroid disease in hospitalized patients. Clin Chem 1987; 33:1391–1396. 20. Re RN, Kourides IA, Ridgway EC, Weintraub BD, Maloof F. The effect of glucocorticoid administration on human pituitary secretion of thyrotropin and prolactin. J Clin Endocrinol Metab 1976; 43:338–346. 21. Vogel R. Rational use of thyroid function tests. Crit Rev Clin Lab Sci 1997; 34:405– 438. 22. Toft AD. Use of sensitive immunoradiometric assay for thyrotropin in clinical practice. Mayo Clin Proc 1988; 63:1035–1042. 23. Nelson JC, Tomei RT. Direct determination of free thyroxine in undiluted serum by equilibrium dialysis. Clin Chem 1988; 34:1737–1744.

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24. Nelson JC, Wilcox RB. Analytical performance of free and total thyroxine assays. Clin Chem 1996; 42:146–154. 25. Kaptein EM. Clinical application of free thyroxine determinations. Clin Lab Med 1993; 13: 653–672. 26. Wilkins TA, Midgley JEM, Barron N. Comprehensive study of a thyroxin-analog-based assay for free thyroxin. Clin Chem 1985; 31:1644–1653. 27. Wilkins TA. Free thyroxin assays; analogue methods. Lancet 1985; 2:884. 28. Deam D, Goodwin M, Ratnaike S. Comparison of four methods for free thyroxin. Clin Chem 1991; 37(4):569–572. 29. Bayer MF. Effective laboratory evaluation of thyroid status. Med Clin North Am 1991; 75: 1–26. 30. Zucchelli GC, Pilo A, Chiesa MR, Masini S. Systematic differences between commercial immunoassays for free thyroxine and free triiodothyronine in an external quality assessment program. Clin Chem 1994; 40:1956–1961. 31. Ekins R. Analytic measurements of free thyroxine. Clin Lab Med 1993; 13:599–630. 32. Liewendahl K, Mahonen H, Tikanoja S, Helenius T, Turula M, Valimaki M. Good correlation between free thyroid hormone concentrations as measured by equilibrium dialysis and analog radioimmunoassays. Clin Chem 1986; 32:2209–2210. 33. Surks MI, Hupart KH, Pan C, Shapiro LE. Normal free thyroxine in critical nonthyroidal illnesses measured by ultrafiltration of undiluted serum and equilibrium dialysis. J Clin Endocrinol Metab 1988; 67:1031–1039. 34. Sapin R, Gasser F, Schlienger JL. Familial dysalbuminemic hyperthyroxinemia and thyroid hormone autoantibodies: interference in current free thyroid hormone assays. Hormone Res 1996; 45:139–141. 35. West CD, Chavre VJ, Wolfe M. A serum thyroxine method: application in thyroid disease and iodine-treated patients. J Clin Endocrinol Metab 1965; 25:1189–1195. 36. Chopra IJ. A radioimmunoassay for measurement of thyroxine in unextracted serum. J Clin Endocrinol Metab 1972; 34:938–947. 37. Borst GC, Eil C, Burman KD. Euthyroid hyperthyroxinemia. Ann Intern Med 1983; 98:366– 378. 38. Tareen AK, Baseer A, Jaffry HF, Shafiq M. Thyroid hormone in hyperemesis gravidarum. J Obstet Gynaecol 1995; 21:497–501. 39. Magner JA, Petrick P, Menezes-Ferreira MM, Stelling M, Weintraub BD. Familial generalized resistance to thyroid hormones: report of three kindreds and correlation of patterns of affected tissues with the binding of [125I] triiodothyronine to fibroblast nuclei. J Endocrinol Invest 1986; 9:459–470. 40. Rajan MGR, Samuel AM. A two-step radioimmunoassay for free triiodothyronine in serum. Clin Chem 1987; 33:372–376. 41. Klee GG. Clinical usage recommendations and analytic performance goals for total and free triiodothyronine measurements. Clin Chem 1996; 42:155–159. 42. Chopra IJ, Hershman JM, Pardridge WM, Nicoloff JT. Thyroid function in nonthyroidal illnesses. Ann Intern Med 1983; 98:946–957. 43. Solomon B, Glinoer D, Lagasse R, Wartofsky L. Current trends in the management of Graves’ disease. J Clin Endocrinol Metab 1990; 70:1518–1524. 44. Hayes AA, Akre CM, Gorman CA. Iodine-131 treatment of Graves’ disease using modified early iodine-131 uptake measurements in therapy dose calculations. J Nucl Med 1990; 31: 519–522. 45. Reading CC, Gorman CA. Thyroid imaging techniques. Clin Lab Med 1993; 13:711–724. 46. Lakshmanan M, Schaffer A, Robbins J, Reynolds J, Norton J. A simplified low iodine diet in I-131 scanning and therapy of thyroid cancer. Clin Nucl Med 1988; 13:866–868. 47. McKenzie JM, Zakarija M. Clinical review 3. The clinical use of thyrotropin receptor antibody measurements. J Clin Endocrinol Metab 1989; 69:1093–1096.


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48. Demers LM, Spencer CA. Laboratory medicine practice guidelines: laboratory support for the diagnosis and monitoring of thyroid disease. American Thyroid Association Guidelines Committee, 2000. 49. Morgenthaler NG, Pampel I, Aust G, Seissler J, Scherbaum WA. Application of a bioassay with CHO cells for the routine detection of stimulating and blocking autoantibodies to the TSH-receptor. Horm Metab Res 1998; 30:162–168. 50. Feldt-Rasmussen U. Analytical and clinical performance goals for testing autoantibodies to thyroperoxidase, thyroglobulin, and thyrotropin receptor. Clin Chem 1996; 42:160–163. 51. Loeffler M, Zakarija M, McKenzie JM. Comparisons of different assays for the thyroid-stimulating antibody of Graves’ disease. J Clin Endocrinol Metab 1983; 57:603–608. 52. Gupta MK. Thyrotropin receptor antibodies: advances and importance of detection techniques in thyroid diseases. Clin Biochem 1992; 25:193–199. 53. Costagliola S, Morgenthaler NG, Hoermann R, Badenhoop K, et al. Second generation assay for thyrotropin receptor antibodies has superior diagnostic sensitivity for Graves’ disease. J Clin Endocrinol Metab 1999; 84(1):90–97. 54. Watson PF, Ajjan RA, Phipps J, Metcalfe R, Weetman AP. A new chemiluminescent assay for the rapid detection of thyroid stimulating antibodies in Graves’ disease. Clin Endocrinol 1998; 49:577–581. 55. Evans C, Morgenthaler NG, Lee S, Llewellyn DH, Clifton-Bligh R, John R, Lazarus JH, Chatterjee VK, Ludgate M. Development of a luminescent bioassay for thyroid stimulating antibodies. J Clin Endocrinol Metab 1999; 84:374–377. 56. Wallaschofski H, Paschke R. Detection of thyroid stimulating (TSAB)- and thyrotropin stimulation blocking (TSBAB) antibodies with CHO cell lines expressing different TSH receptor numbers. Clin Endocrinol 1999; 50:365–372. 57. Feldt-Rasmussen U, Schleusener H, Carayon P. Meta-analysis evaluation of the impact of thyrotropin receptor antibodies on long term remission after medical therapy of Graves’ disease. J Clin Endocrinol Metab 1994; 78:98–102. 58. Cho BY, Shong MH, Yi KH, Lee HK, Koh CS, Min HK. Evaluation of serum basal thyrotropin levels and thyrotropin receptor antibody activities as prognostic markers for discontinuation of antithyroid drug treatment in patients with Graves’ disease. Clin Endocrinol 1992; 36:585– 590. 59. Bliddal H, Kirkegaard C, Sierbaek-Nielsen K, Friis T. Prognostic value of thyrotropin binding inhibiting immunoglobulins (TBII) in long-term antithyroid treatment, 131I therapy given in combination with carbimazole and in euthyroid ophthalmopathy. Acta Endocrinol 1981; 98: 364–369. 60. Kazuo K, Fujikado T, Ohmi G, Hosohata, J, Tano Y. Value of thyroid stimulating antibody in the diagnosis of thyroid associated ophthalmopathy of euthyroid patients. Br J Ophthalmol 1997; 81(12):1080–1083. 61. Gerding MN, van der Meer JWC, Broenink M, Bakker O, Wiersinga WM, Prummel MF. Association of thyrotropin receptor antibodies with the clinical features of Graves’ ophthalmopathy. Clin Endocrinol 2000; 52:267–271. 62. Zakarija M, McKenzie JM. Pregnancy-associated changes in the thyroid stimulating antibody of Graves’ disease and the relationship to neonatal hyperthyroidism. J Clin Endocrinol Metab 1983; 57:1036–1040.

6 Basic Concepts of the Immune System R. CHRISTOPHER WALTON University of Tennessee Health Science Center, Memphis, Tennessee, U.S.A.

The immune system is a complex organization of tissues, cells, and molecules located throughout the body that function to protect the host from foreign antigens. To accomplish its tasks, the immune system is organized into a network consisting of centralized cellular production with peripheral immune surveillance. Immune responses occur in a number of sites including the spleen, local lymph nodes, mucosa-associated lymphoid tissues, palatine tonsils, adenoids, and Peyer’s patches, depending upon the location of the antigen. For micro-organisms located in tissues, the immune response is initiated in local lymph nodes. The spleen is the site for immune responses against bloodborne antigens. This dynamic system can produce a diverse number of cells and molecules that can specifically recognize and eliminate a seemingly infinite number of foreign antigens. Along with this tremendous diversity, the immune system has evolved a number of regulatory mechanisms to limit the activation and effector functions of the immune response. This serves to limit the magnitude of immune responses to various pathogens, thereby avoiding potentially harmful effects. These mechanisms are also critical for the development of tolerance or unresponsiveness to self antigens. Failure of these mechanisms can result in autoimmune reactions and the development of autoimmune diseases. This chapter will introduce the basic concepts of the immune system. The discussion will focus on topics important to the understanding of the immunopathogenesis of thyroid eye disease. I.

OVERVIEW OF THE IMMUNE SYSTEM

The immune system responds to foreign antigens by utilizing two interdependent mechanisms: innate and acquired (adaptive) immunity. Innate immunity provides the initial host 41

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defense against infectious agents. It is a rapid, nonspecific response and consists of a variety of cellular components including nonspecific phagocytes such as neutrophils and macrophages, granulocytes that release chemical mediators, and natural killer cells. The innate response also includes the acute phase proteins, complement, and numerous cytokines (1). However, the innate response lacks immunological memory and therefore does not change in response to repeated encounters with an antigen. The acquired immune response, on the other hand, is capable of recognizing and eliminating specific foreign antigens. Acquired immunity has several features that differentiate it from innate immunity. First is the ability to discriminate differences among a large number of antigens. It also allows for the generation of extensive diversity within its recognition molecules. Acquired immunity also has the ability to differentiate self from nonself antigens. Finally, the acquired immune response has the ability to develop immunological memory whereby the response improves with repeated exposure to an antigen. Several phases characterize the acquired immune response. The afferent phase involves the recognition of the antigen by an antigen-presenting cell (APC), transport to the peripheral lymph node, and presentation to lymphocytes within the lymph node. During the next phase, lymphocytes are activated within the lymphoid tissues. Finally, during the effector phase, lymphocytes help other inflammatory cells including macrophages and B cells to eliminate the antigen.

II. COMPONENTS OF THE IMMUNE SYSTEM The immune system consists of a variety of cells and soluble mediators. Cells of the innate response include neutrophils, macrophages, monocytes, basophils, eosinophils, mast cells, and natural killer cells. Neutrophils are nonspecific phagocytes that function to remove most extracellular antigens as well as the body’s own dying or dead cells (2). Basophils, eosinophils, and mast cells participate in the innate response by releasing the contents of cytoplasmic granules as well as secreting inflammatory mediators including prostaglandins, leukotrienes, histamine, and cytokines. Natural killer cells, or large granular lymphocytes, destroy virus-infected cells as well as tumor cells (3). Macrophages and dendritic cells participate in both innate and acquired immune responses. As participants in the innate response, both cell types phagocytose or endocytose foreign antigens. Macrophages also secrete inflammatory cytokines that are responsible for the recruitment of other inflammatory cells to sites of inflammation. Macrophages and dendritic cells also have important roles in the acquired immune response where they serve as APCs. The acquired immune response utilizes two major groups of cells: the mononuclear phagocytes and lymphocytes. The mononuclear phagocytes consist of monocytes, macrophages, and dendritic cells. All of these cells originate from a common stem cell precursor in the bone marrow. Monocytes circulate in the peripheral blood and mature into macrophages after arriving in various tissues. In the acquired immune response, macrophages serve as antigen-presenting cells by displaying foreign antigen on their cell surface. These antigens can then be recognized by antigen-specific T lymphocytes. The macrophages also function as one of the primary effector cells of the acquired immune response. During the effector phase of the acquired immune response, macrophages become activated, thereby allowing more efficient destruction of phagocytosed pathogens. Macrophages also participate in humoral immunity by binding and phagocytosing antigens that have been coated with antibody with greater affinity than uncoated antigens.

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Dendritic cells are important in the initiation of most immune responses. There are two types of dendritic cells: the interdigitating dendritic cells (usually called ‘‘dendritic cells’’) and follicular dendritic cells (4). Dendritic cells are located in the skin and most organs as well as the T-cell regions of the lymph nodes and spleen. They have several functions including the endocytosis of extracellular antigens and, if activated, serve as APCs (5,6). Activated dendritic cells serve as APCs by migrating to regional lymph nodes where they present antigen to T cells. In contrast, follicular dendritic cells are not related to the interdigitating dendritic cells and are located within the germinal centers of lymph nodes and the spleen as well as mucosal-associated lymphoid tissues. The function of these cells is to present antigen to B cells. The other major group of cells that participate in the acquired immune response are the lymphocytes. These are unique in that they are the only cells that have the ability to recognize and discriminate between the different antigens they encounter. Three major groups of lymphocytes exist: T lymphocytes, B lymphocytes, and natural killer cells. Similarly to the mononuclear phagocytes, these cells arise from a common stem cell precursor in the bone marrow. B lymphocytes mature in the bone marrow and T lymphocytes mature in the thymus. Both B and T lymphocytes participate in clonally specific immune responses while natural killer cells are responsible for the recognition and killing of abnormal cells (e.g., virus-infected cells and tumor cells). Both B cells and T cells are activated by the binding of antigen to specific cell surface receptors. The secreted products and membrane receptors of B cells are immunoglobulin (antibody) molecules. The B-cell receptor consists of a cell-surface immunoglobulin that binds antigen to initiate clonal expansion and differentiation of B cells into antibody-producing plasma cells. Immunoglobulins are glycoproteins containing two identical heavy chains and two identical light chains (Fig. 1). The two heavy chains are attached to each other by disulfide bonds and one light chain is attached to each heavy chain (7,8). The amino terminal domains of each chain form the antigen-binding variable region of the immunoglobulin while the carboxy terminal domains form the constant region of the immunoglobulin. The constant region specifies the class (IgA, IgD, IgE, IgG, and IgM) and subclass of each immunoglobulin. Mature B lymphocytes leave the bone marrow and enter the peripheral circulation and lymphoid tissues. Activation of these mature cells can then occur by two different mechanisms. Direct activation occurs when certain antigens are recognized by the B-cell receptor. These antigens are typically polysaccharides or other antigens with repeating epitopes such as the capsular polysaccharides of certain bacteria. The other mechanism involves T lymphocyte–dependent antigens that have been processed by the B cell and expressed on the cell membrane complexed with class II major histocompatibility complex (MHC) molecules. T helper cells recognize the antigen–MHC class II molecule complex and bind to the B cell, resulting in activation. Activation of mature B lymphocytes promotes terminal differentiation of the cell into an antibody-secreting plasma cell or a memory cell. Memory cells produce antibody as part of the secondary response that occurs with repeated exposure to an antigen. Following antigenic stimulation, B cells also undergo two processes: immunoglobulin class switching and affinity maturation. In class switching, mature B cells are stimulated by T helper cells and cytokines to produce different classes of antibodies. This heavy chain class switching occurs as a result of several DNA recombination events and allows a B cell that produces one immunoglobulin to differentiate into a cell that can produce a different immunoglobulin (9). As a result, the immunoglobulin retains its antigen specific-

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Figure 1 Schematic diagram of a membrane-bound IgG molecule. Each molecule consists of two heavy and two light chains connected by interchain disulfide bonds (S–S). Each heavy chain has four domains: three constant (CH ) and one variable (VH ). The light chains contain one constant (CL ) and one variable (VL ) domain. The antigenbinding site is located at the amino (NH2) terminal region and formed by the variable domains of both the heavy and light chains.

ity while the effector mechanisms of the molecule vary depending upon the specific class of antibody produced. The second process of affinity maturation occurs as a result of somatic hypermutation. Within the germinal centers of secondary lymphoid tissues, B cells undergo this somatic hypermutation in which a large number of somatic mutations occur, especially within the variable region genes of the heavy and light chains (10). These mutations will generate increased antibody diversity and determine the strength of antibody binding (affinity). As the concentration of an antigen decreases, those B cells with a higher affinity for the antigen will have a greater chance for survival than those with low affinity (11). The surviving clones of B cells will produce higher-affinity antibodies with re-exposure to the antigen. This affinity maturation occurs only in antibody responses to T-helper-cell-dependent antigens (12). The T-cell receptor (TCR) is a transmembrane heterodimer that functions to recognize antigen presented in association with an MHC molecule. The domain structure of the TCR is similar to that of the immunoglobulins and B-cell receptor (Fig. 2). Most T-


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Figure 2 Diagram of a T-cell receptor. The T-cell receptor is a cell-membrane-bound heterodimer. Each polypeptide chain is linked by disulfide bonds and contains a constant (C) and variable (V) domain similar to those of the B-cell receptor. cell receptors are composed of an α and β chain (αβ TCR), although some T cells express the γδ TCR (13). Each polypeptide chain contains one constant and one variable domain that are each structurally homologous, respectively, to the constant and variable domains of the B-cell receptor and immunoglobulins. However, the TCR differs from the B-cell receptor in two ways. First, the TCR is produced only as a membrane-bound molecule and does not have a circulating form similar to the immunoglobulins. Second, the TCR is not specific for antigen alone but instead recognizes the specific antigen only if it is associated with an MHC molecule. There are two major types of T lymphocytes: CD4⫹ T cells (T helper) and CD8⫹ T cells (T suppressor). The CD4 and CD8 cell-surface molecules help T cells to recognize specific MHC molecules and serve as coreceptors for the TCR. T helper cells recognize antigen combined with MHC class II molecules and function primarily by secreting cytokines, thereby helping other cells mediating the immune response. T suppressor cells recognize antigen combined with an MHC class I molecule and function as cytotoxic killer cells and eliminate virally infected cells (11). T helper cells can be further classified into two subsets of cells: type 1 and type 2 (Th1 and Th2) helper T cells (14). Th1 helper T cells secrete interleukin-2 and interferon-γ and promote cell-mediated immunity, including the activation of macrophages and T cell-mediated cytotoxicity. Th2 helper T cells secrete interleukin-4, -5, -6, and -10 and function to help B cells produce antibodies, stimulate mast cell development, and activate eosinophils. Th2 cells also may act as regulators of immune responses by antagonizing the effects of Th1 cells. III. MAJOR HISTOCOMPATIBILITY COMPLEX The major histocompatibility complex is a region of highly polymorphic genes located along a region of chromosome 6 in humans. The products of the MHC play a central role

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in both cell-mediated and humoral immune responses. Most T cells recognize antigen only when it is complexed with an MHC molecule. Therefore, the specific haplotype of MHC molecules expressed by an individual determines the range of antigens to which the T cells are able to respond (15). Both class I and II MHC molecules are membranebound glycoproteins that function by binding peptides of foreign antigens and forming complexes that are recognized by T cells. Class I MHC molecules consist of two polypeptide chains: a large α chain and a β2-microglobulin molecule (Fig. 3). The α chain is a transmembrane glycoprotein containing three external domains that are noncovalently associated with β2-microglobulin. The α1 and α2 domains interact to form the peptide-binding cleft on the top of the class I molecule. This peptide-binding cleft is able to bind peptides from 8 to 10 amino acids in length. These peptides have been processed within the cytoplasm and are derived from endogenous antigens such as normal cellular proteins, viral proteins, or tumor proteins. The class I MHC molecule–peptide complex is transported to the cell membrane and recognized by specific CD8⫹ T cells that function to kill any cell that they recognize. Class II MHC molecules also contain two polypeptide chains: an α and β chain. Both chains are transmembrane glycoproteins that form a noncovalent complex (Fig. 4). The α1 and β1 domains form the peptide-binding cleft on the top of the class II molecule. The MHC class II binding cleft is open at both ends and allows binding of much larger peptides than those bound by class I MHC molecules. Peptides that bind to class II molecules have been processed within intracellular vesicles and are at least 13 amino acids in length. These peptides are from antigens that have been internalized by phagocytosis or endocytosis. The class II MHC molecule–peptide complexes move to the plasma membrane where they are recognized by CD4⫹ T cells that activate B cells to form antibody or activate macrophages to destroy the pathogen.

Figure 3 Structure of the class I MHC molecule. Each molecule consists of a large α chain noncovalently associated with a β2-microglobulin molecule. The α chain contains three domains: α1, α2 , α3 . The peptide binding cleft is formed by the interaction of the α1 and α2 domains.


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Figure 4 Schematic diagram of the class II MHC molecule. Class II molecules are membrane-bound glycoproteins containing two polypeptide chains that are noncovalently linked. Each chain contains an α and β domain. The interaction of the α1 and β1 domains forms the peptide-binding cleft of the class II molecule.

IV.

ACQUIRED IMMUNE RESPONSES

All immune responses can be classified into three basic phases: recognition, activation, and the effector phase. The acquired immune response occurs as a result of proliferation of antigen-specific T and B cells and typically begins with the uptake of antigen at the site of inflammation. At these sites, antigen-presenting cells phagocytose antigen and then migrate to the regional lymph nodes or spleen. Extracellular antigens enter APCs by phagocytosis or endocytosis, are processed by lysosomes or endosomes, and the resulting peptides are loaded into class II MHC molecules. The peptide–class II MHC complex is expressed at the cell surface where it can be recognized by CD4⫹ T cells. Intracellular antigens produced by virally infected cells and other intracellular microbes are processed within the cytoplasm. These peptide fragments are loaded into class I MHC molecules and transported to the cell surface for presentation to CD8⫹ T cells. The recognition phase occurs within specific regions of the lymph nodes and spleen where APCs present antigen to both T and B cells. The B-cell receptor recognizes native (unprocessed) antigens while the αβ TCR recognizes processed antigens complexed with MHC molecules. Activation of both B and T lymphocytes requires binding of the appropriate receptor as well as additional signals from a variety of costimulatory molecules on APCs and soluble mediators including interleukin-6, interleukin-1, and tumor necrosis factor α (11,16–18). Activation of T lymphocytes results in clonal proliferation and differentiation into effector and memory cells. B lymphocyte activation occurs in the germinal centers of lymphoid tissues resulting in affinity maturation, class switching, and differentiation into antibody-producing plasma cells and memory cells.

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During the effector phase, activated lymphocytes perform functions that ultimately result in the elimination of specific antigens. This phase includes a variety of effector responses such as antibody binding to antigens, antibody activation of the complement cascade, antibody-enhanced phagocytosis, and antibody-dependent cellular cytotoxicity. Type 1 T helper cells produce cytokines that activate macrophages and T-cell-dependent cytotoxicity while type 2 T helper cells stimulate B cells to produce antibodies (11). The CD8⫹ T cells destroy virally infected cells and produce cytokines that protect adjacent cells from infection (19). Therefore, the effector phase is characterized by an interaction of both innate and acquired immune responses to eliminate foreign antigens.

V.

AUTOIMMUNITY

The immune system does not normally recognize and respond to self antigens, thereby preventing harmful reactions against an individual’s own antigens. A critical property of the immune system is this ability to differentiate self from nonself antigens, also known as self-tolerance. Self-tolerance is a process involving several active mechanisms that prevents the maturation or activation of self-reacting lymphocytes. The two principal mechanisms involved in tolerance are clonal deletion, in which antigen-specific clones are deleted by apoptosis; and clonal anergy or induction of unresponsiveness against selfreactive cells within the thymus and peripheral tissues (20). Autoimmunity occurs when there is a failure in the normal mechanism of self-tolerance, resulting in an immune reaction against self antigens. Several factors may contribute to the development of autoimmunity including genetic susceptibility, gender, immunological abnormalities affecting antigen-presenting cells or lymphocytes, microbial infections, and environmental factors. Autoimmune disease occurs when an immune response is directed against self antigens, resulting in chronic tissue damage. Graves’ disease is an autoimmune disorder of the thyroid gland that is caused by thyroid-stimulating antibodies (21). The thyroid cells are both the source and target of these autoantibodies. The disease appears to occur in genetically susceptible individuals, although environmental and endogenous factors may contribute to the development of the disease (22). Patients with Graves’ disease exhibit a variety of immunological abnormalities that are highly suggestive of autoimmunity, including diffuse lymphocytic infiltration of the thyroid gland and sensitization to several thyroid antigens as well as the thyrotropin receptor (20,23). One of the important autoantigens in this disorder is the thyrotropin receptor. Autoantibodies to this receptor probably stimulate the production of excessive amounts of glycosaminoglycans in a variety of cells of the orbit (20,21,24). As a result, the orbital fatty tissues expand and the extraocular muscles enlarge, leading to the familiar clinical signs of Graves’ ophthalmopathy. The TSH receptor is thought to be the major autoantigen in patients with Graves’ disease, although it remains unclear if it contributes to the pathogenesis of Graves’ ophthalmopathy (23,25). However, several studies have shown that TSH receptors are expressed by fibroblasts and other orbital tissues from patients with Graves’ ophthalmopathy (21,26,27). Recently, an animal model has been developed that has features similar to Graves’ ophthalmopathy (28). This model utilizes the transfer of TSH receptor-primed T cells to naı¨ve mice to induce thyroiditis and orbital pathology. The orbital changes include orbital infiltration by lymphocytes, edema, TSH receptor immunoreactivity, and periodic acid–Schiff-positive material between muscle fibers. Although these findings are similar


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to those in patients with Graves’ disease, it remains unclear if this model reflects the true pathogenesis of Graves’ ophthalmopathy. REFERENCES 1. Fearon DT, Locksley RM. The instructive role of innate immunity in the acquired immune response. Science 1996; 272:50–53. 2. Delves PJ, Roitt M. The immune system. First of two parts. N Engl J Med 2000; 343:37–49. 3. Biron CA, Nguyen KB, Pien GC, Cousens LP, Salazar-Mather TP. Natural killer cells in antiviral defense: function and regulation by innate cytokines. Annu Rev Immunol 1997; 17: 189–220. 4. Abbas AK, Lichtman AH, Pober JS. Cellular and Molecular Immunology. 3rd ed. Philadelphia: WB Saunders, 1997: Chap. 2. 5. Bell D, Yond JW, Banchereau J. Dendritic cells. Adv Immunol 1999; 72:255–324. 6. Medzhitov R, Janeway CA Jr. Innate immunity: impact on the adaptive immune response. Curr Opin Immunol 1997; 9:4–9. 7. Silverton EW, Navia MA, Davies DR. Three-dimensional structure of an intact human immunoglobulin. Proc Natl Acad Sci USA 1977; 74:5140–5144. 8. Alzari PM, Lascombe M, Poljak RJ. Three-dimensional structure of antibodies. Annu Rev Immunol 1988; 6:555–580. 9. Stavnezer J. Antibody class switching. Adv Immunol 1996; 61:79–146. 10. Wagner SD, Neuberger MS. Somatic hypermutation of immunoglobulin genes. Annu Rev Immunol 1996; 14:441–457. 11. Delves PJ, Roitt IM. The immune system. Second of two parts. N Engl J Med 2000; 343: 108–117. 12. Abbas AK, Lichtman AH, Pober JS. Cellular and Molecular Immunology. 3rd ed. Philadelphia: WB Saunders, 1997: Chap. 4. 13. Goldsby RA, Kindt TJ, Osborne BA. Kuby Immunology. 4th ed. New York: WH Freeman, 2000: Chap. 9. 14. Mosmann TR, Sad S. The expanding universe of T-cell subsets: Th1, Th2 and more. Immunol Today 1996; 17:138–146. 15. Goldsby RA, Kindt TJ, Osborne BA. Kuby Immunology. 4th ed. New York: WH Freeman, 2000: Chap. 7. 16. Lenschow DJ, Walunas TL, Bluestone JA. CD28/B7 system of T cell costimulation. Annu Rev Immunol 1996; 14:233–258. 17. Justement LB. The role of CD45 in signal transduction. Adv Immunol 1997; 66:1–65. 18. Joseph SB, Miner KT, Croft M. Augmentation of naive Th1 and Th2 effector CD4 responses by IL-6, IL-1, and TNF. Eur J Immunol 1998; 28:277–289. 19. Mosmann TR, Li L, Sad S. Functions of CD8 T-cell subsets secreting different cytokine patterns. Semin Immunol 1997; 9:87–92. 20. McIver B, Morris JC. The pathogenesis of Graves’ disease. Endocrinol Metab Clin North Am 1998; 27:73–89. 21. Weetman AP. Graves’ disease. N Engl J Med. 2000; 343:1236–1248. 22. Brix TH, Kyvik KO, Hegedus L. What is the evidence of genetic factors in the etiology of Graves’ disease? A brief review. Thyroid 1998; 8:627–634. 23. Bahn RS. Understanding the immunology of Graves’ ophthalmopathy. Is it an autoimmune disease? Endocrinol Metab Clin North Am 2000; 29:287–296. 24. Heufelder AE, Spitzweg C. Immunology of Graves’ ophthalmopathy. Dev Ophthalmol 1999; 30:24–38. 25. Graves PN, Davies TF. New insights into the thyroid-stimulating hormone receptor. The major antigen of Graves’ disease. Endocrinol Metab Clin North Am 2000; 29:267–286.

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26. Heufelder AE, Dutton CM, Sarkar G, Donovan KA, Bahn RS. Detection of TSH receptor RNA in cultured fibroblasts from patients with Graves’ ophthalmopathy and dermopathy. Thyroid 1993; 3:297–300. 27. Mengistu M, Lukes YG, Nagy EV, Burch HB, Carr FE, Lahiri S, Burman KD. TSH receptor expression in retroocular fibroblasts. J Endocrinol Invest 1994; 17:437–441. 28. Many M-C, Costagliola S, Detrait M, Denef J-F, Vassart G. Ludgate M. Development of an animal model of autoimmune thyroid eye disease. J Immunol 1999; 162:4966–4974.

7 Mechanisms of Immune Self-Tolerance JACQUES F. A. P. MILLER Royal Melbourne Hospital, Victoria, Australia

The immune system has provided us with a powerful weapon against infection, eliminating micro-organisms and killing infected cells. Part of this task is performed by lymphocytes that have randomly generated a great diversity of antigen-specific receptors. But there is a problem created by diversity, and that is the need to delete lymphocytes not just responsive to self, but, more importantly, aggressive toward self. What, then, is self? Higher organisms possess an innate ability to differentiate species self from the infectious nonself of micro-organisms, by means of various pattern recognition molecules, such as complement, collectins, and lipopolysaccharide-binding proteins (1). The nonadaptive immune response has indeed evolved specifically to recognize molecular structures that are unique to bacteria and not found in cells of higher organisms (e.g., in mammalian cells). This provides an elementary but very powerful discrimination between self and nonself. But are there any self characteristics, at the molecular level, that might differentiate one individual of a species like ours from any other individual of the same species? Perhaps we might suggest the following. For the immune system, self includes all antigenic determinants (epitopes) encoded in the individual’s own DNA, all other epitopes being considered as nonself. How then does the immune system differentiate self from nonself? No mechanism can possibly exist to allow the system to scrutinize the entire germline DNA, its translation products, and those that are subsequently modified. Could some unique structural properties perhaps be attributed to self epitopes? In their book, The Production of Antibodies, Burnet and Fenner (2) stated ‘‘Body cells carry ‘self marker’ components which allow recognition of their ‘self ’ character. Antigens in general are substances of the same chemical nature as the marker components but of different molecular configuration.’’ There is, however, no evidence that primary or secondary structure alone 51

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is what determines the ability of the immune system to differentiate self from nonself epitopes. Attributes other than the structural characteristics of an epitope must also be sensed. Among these, the following have been suggested to play an important role: 1. 2. 3. 4. 5. 6. I.

Stage of development of the individual Stage of development of the lymphocyte Site of encounter (primary lymphoid organs [thymus or bone marrow], secondary lymphoid tissues, parenchymal tissues) Nature of cells presenting epitopes (antigen-presenting cells [APCs], parenchymal tissue cells) Production of nonepitope chemical products (costimulatory molecules, cytokines) ‘‘Danger’’

STAGE OF DEVELOPMENT OF THE INDIVIDUAL OR OF THE LYMPHOCYTE

The first of the above attributes, suggested by Burnet and Fenner (2), seemed logical, since the immune system is usually confronted with most self components before birth and only later with nonself antigens. The classic experiments of Billingham and colleagues, performed in 1953 (3), thoroughly vindicated this hypothesis. Whereas injection of allogeneic cells in the adult produced an accelerated response to a subsequent skin graft from the same donor, injecting these cells at birth or in fetal life induced specific tolerance to the skin allografts (Fig. 1). This phenomenon of tolerance could easily be interpreted in

Figure 1 Bone marrow cells from strain B mice are injected intravenously into less than 1-day-old newborn mice of strain A. When these mice are subsequently grafted in adult life with skin from strains B and C, they can reject strain C skin, but not strain B skin and hence are specifically tolerant to tissue antigens of strain B. (From Ref. 3.)

Mechanisms of Immune Self-Tolerance

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terms of Burnet’s clonal selection theory (4). Antigen encountered before birth would delete the clones which Burnet termed ‘‘forbidden clones,’’ whereas antigen encountered after birth would activate specific clones to proliferate and respond. Implicit in this theory is the requirement for prenatal generation of the entire immune repertoire. This is, of course, not the case since lymphocyte differentiation continues in postnatal life and probably throughout most of life, and somatic mutation generates new B-cell specificities after antigenic stimulation. Thus, the key factor in determining responsiveness, whether tolerance or immunity, cannot be the development stage of the individual but the state of maturity of the lymphocyte at the time it encounters antigen. This was pointed out by Lederberg in 1959 (5) in his modification of Burnet’s clonal selection theory. Immature lymphocytes encountering antigen would be deleted, whereas mature lymphocytes would be activated to respond. Although strong evidence has been obtained to support this idea, this simple and elegant scheme cannot accommodate many experimental situations, as will be seen below. In Burnet’s laboratory, Nossal (6) failed to induce tolerance in mice even after injection of influenza virus in utero, a failure presumably due to rapid antigen clearance. By contrast, tolerance to the immunogenic form of a protein could be induced by preinoculation of the protein in deaggregated form in adult mice (7), which of course possess many mature lymphocytes. Likewise, tolerance to synthetic polypeptides could easily be achieved in the adult (8). Hence, contact of mature lymphocytes with antigen does not always lead to an immune response. Although lymphocytes in neonatal mice were thought to be immature, because of the ease with which tolerance to allografts could be induced at that age, it is clear that neonatal mouse T cells are perfectly able to mount an immune response to antigen, as was shown more than 20 years ago when the T cells of 1-day-old mice reacted strongly to foreign antigens (9). II. INTRATHYMIC TOLERANCE What about immature T cells in the thymus? Are they always deleted when they encounter antigen? The first hint that the thymus may be involved in tolerance induction came from experiments in which neonatally thymectomized mice were grafted with syngeneic or allogeneic thymus tissue. Whereas nongrafted mice were severely immunodeficient (10), those given syngeneic thymus grafts were perfectly immunocompetent, while those receiving allogeneic grafts were also competent except insofar as they were specifically tolerant to tissues from the donor of the thymus graft (11) (Fig. 2). It was suggested that the tolerance caused by injecting allogeneic cells at birth induced a so-called immunological thymectomy, that is, it deleted those host thymus lymphocytes specifically reactive to the antigens on the donor cells (11). It is now well established that immature T cells in the thymus can either be deleted or selected for survival by the same self antigen (peptide) (12–14). Developing T cells are positively selected for survival only if they can express an antigen-specific receptor (T-cell receptor [TCR]) that enables them to bind with a certain degree of strength (avidity) to molecules encoded by the major histocompatibility complex (MHC) and encountered on thymic cortical epithelial cells (Fig. 3). It is probable that such binding protects the cells from programmed cell death. Positive selection thus ensures that the mature T cell will recognize antigenic epitopes (peptides) accommodated in the binding cleft of self

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Figure 2 Restoring immune function to immunodeficient neonatally thymectomized mice was achieved by grafting thymus tissue. If the tissue was derived from syngeneic mice, the grafted mice were perfectly immunocompetent. If derived from allogeneic mice, the recipients were competent except that they were specifically tolerant of tissues from the strain of mice providing the foreign thymus graft. (From Ref. 11.)

MHC molecules, and hence will be self-MHC restricted. This selection will not, however, prevent the differentiation of T cells with high-avidity TCR for self peptides and MHC molecules. Some form of negative selection must therefore operate to prevent the autoimmune potential of such self-reactive cells. This generally occurs by the physical deletion of those clones of T cells that have high-avidity TCR directed to self-antigens present within the thymus, on thymus dendritic cells, and also on some thymic medullary epithelial cells (14). Thus, the avidity of the TCR for the target self peptide and self MHC molecule dictates whether the selection will be positive or negative.

III. EXTRATHYMIC TOLERANCE Self antigens expressed only outside the thymus may not provoke an immune response if they are sequestered in privileged sites away from the circulating routes of naı¨ve T cells, or exposed on certain cell types that do not express MHC molecules and hence cannot present peptides derived from those antigens to T cells. It may also be the case if the autoantigens are present in amounts too low to be detected by T cells, or if the avidity of the combined TCR and accessory molecules is not high enough for T cells to establish effective contact with the autoantigen-presenting cells. Under these conditions, the naı¨ve T cells ignore the existence of the autoantigens (15) but the resulting lack of T cell activation is not equivalent to tolerance induction since presentation of the autoantigen by professional APCs would immunize. Fail-safe mechanisms inducing postthymic tolerance must, however, exist since molecules may be released from dying cells and hence processed and presented by professional APCs, such as macrophages or dendritic cells. Because


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Figure 3 Development pathways of thymocytes expressing the αβ TCR and the CD4

(4⫹) and CD8 (8⫹) coreceptors showing the stages at which positive and negative selection operate (see text). Here, avidity is towards self peptide accommodated in the cleft of self MHC molecules.

these APCs have costimulatory function, they are well equipped to activate T cells (see below). If contact does occur between postthymic mature T cells and antigens, the result may not always be a productive immune response. Thus, under conditions of antigen persistence, T-cell apoptosis results and operational tolerance may follow. For example, high doses of a particular strain of the lymphocytic choriomeningitis virus caused the differentiation of presumably all virus-specific CD8⫹ T cells to cytolytic lymphocytes, which reached maximum levels at 6 days and then declined to undetectable levels at 15 days as a result of apoptosis. The virus was not cleared and persisted (16). Figure 4 shows three pathways in which antigen may be presented to T cells. When parenchymal tissue self antigens are cross-presented above a certain critical level in the draining lymph nodes, apoptosis of any self-reactive CD8⫹ T cells present there at the time will occur (17). This was demonstrated in work using mice transgenic for a TCR directed to the major peptide of the ovalbumin (OVA) molecule. When these transgenic T cells (OT-I cells) were confronted in the periphery of other transgenic mice expressing the target antigen as a self antigen in the β cells of the islets of the pancreas, the following events were observed (17):

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Figure 4 Pathways of antigen presentation to extrathymic, mature CD4⫹ and CD8⫹ T lymphocytes. CD4⫹ T cells generally recognize antigenic determinants in association with MHC class II molecules on the surface of APCs that have taken up the antigen exogenously and processed it intracellularly. CD8⫹ T cells recognize antigen synthesized within the APC and presented in association with MHC class I molecules (endogenous pathway). They can also recognize antigen taken up by the APC exogenously, processed intracellularly by an as yet undetermined pathway, and presented with MHC class I molecules (cross presentation pathway).

1.

2.

3. 4. 5. 6.

The transgenic self antigen migrated from the islets to the draining lymph nodes where it was recognized by OT-I cells on the surface of APCs. It is presumed that this must be occurring spontaneously and continuously, and in the absence of any inflammatory response or harmful influence. The APCs were derived from bone marrow, had a short life span, and antigen cross-presented by these cells was not only sufficient but also essential for OT-I cell activation. Following activation, the OT-I cells proliferated. After some proliferation, activated OT-I cells disappeared within 4–5 weeks, presumably as a result of activation-induced cell death. Only when 1 million or more OT-I cells were given did diabetes occur. Such a high number of cells of a particular clone is, of course, not physiological. Only relatively high doses of self-antigen were cross-presented; low doses were not unless autoantigen-expressing cells had been damaged.

The situation just described could well mimic the following scenario. Self-reactive T cells that have escaped thymus censorship for one reason or another find their way to the lymph nodes draining a healthy tissue that releases the target self antigen at a certain rate. If this rate is below some threshold level, the naı¨ve T cells (which do not normally circulate into nonlymphoid tissues) (18) will not be activated and hence will ignore their target. If the rate is above that level, the T cells will be activated as soon as they enter the nodes and will eventually succumb to activation-induced cell death. Autoimmune damage will thus not take place under these conditions.


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In fact the failure to induce apoptotic T-cell death is an important factor that accounts for the loss of self tolerance and the development of autoimmunity in animals and patients with a mutation in the genes coding for death receptors (19). In human patients with autoimmune lymphoproliferative syndrome (ALPS), Fas mutations, often found in the Fas death domain, cause defective Fas-mediated lymphocyte apoptosis. A similar syndrome, ALPS II, is also characterized by defective Fas-mediated lymphocyte apoptosis, although these patients do not have Fas or Fas ligand mutations, but rather a mutation in caspase 10, which is a death protease that must be activated for apoptosis to take place. It is of great interest that some patients with caspase 10 mutations had a marked accumulation of dendritic cells, which, in a normal immune response, would be rapidly eliminated (20,21). The failure to eliminate T cells and dendritic cells in ALPS patients must therefore contribute to the autoimmune phenomena.

IV.

COSTIMULATORY ACTIVITIES

In the early 1970s, Bretscher and Cohn (22) claimed that lymphocytes would require two signals in order to respond. Signal 1 alone would switch the cells off and induce tolerance, whereas signals 1 and 2 would lead to an immune response. Lafferty and co-workers (23) extended this idea arguing that the first signal was antigen-specific and the second was a costimulator signal delivered by an APC, such as a dendritic cell. The subsequent discovery of costimulator molecules on APCs and of the powerful immunogenic properties of dendritic cells have added weight to this hypothesis (Fig. 5). But does signal 1 alone, under physiological conditions and in vivo, lead to tolerance or anergy? Apart from the neonatal period, it is well established that naive T cells do not enter nonlymphoid tissues

Figure 5 T cells can be activated by antigen, in association with MHC molecules, if the antigen is presented on the surface of APCs that have costimulator molecules such as B7, as shown on the right. The CD8 coreceptor on the T cells engages the B7 molecule and this effectively costimulates the T cell.

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(18), that is, the very tissues whose cells do not possess costimulatory activity. How, then, could naive T cells be anergized in vivo, since they enter such tissues only after being activated in the draining lymph nodes?

V.

THE DANGER CONCEPT

Matzinger (24) has argued that the immune system, rather than discriminating between self and nonself, does so between harmless and dangerous entities. Of the several examples that are difficult to explain in accordance with the danger hypothesis, two will be singled out for special mention. When one immunizes mice with mouse cytochrome c, one gets no response, but a comparable immunization with pigeon cytochrome c does give a response (25). In both cases, adjuvant containing dangerous and highly immunostimulatory mycobacteria was used. A similar situation is seen in allograft rejection. Allografts do not normally occur in nature and so the immune response could not have evolved to regard these as dangerous. Yet they trigger powerful immune responses (26). The danger from the trauma of surgically implanting the graft cannot account for the rejection, since syngeneic grafts do not provoke a response and are accepted. Yet the inflammation following the surgical procedures would be expected to stimulate the many dendritic cells expressing costimulatory molecules and MHC molecules carrying peptides. Clearly, in both these cases the clonally individuated T cells with high affinity receptors for self MHC and self peptides have been deleted in the thymus (14). Hence at least in the thymus, there is discrimination between self and nonself epitopes rather than between harmless and harmful entities. Yet since, in these examples, there are no self-reactive T cells in the periphery, does the danger concept apply only to situations where there are specific T cells circulating? In the classic experiments of Billingham and colleagues, longstanding (up to 144 days) allografts in healthy immunologically tolerant mice were destroyed following an injection of purified naive lymphocytes from normal unsensitized donors of the same strain as the tolerant host (27). It would be stretching credulity to argue that an intravenous injection mimics a danger signal, particularly as an injection of lymph node cells immune to the tolerated graft, but foreign to the host, did not lead to skin graft rejection. Further doubts concerning the validity of the danger hypothesis have been admirably expressed in a recent article (28). Danger is not excluded as playing any role whatsoever in immune responses. It certainly does in the response to pathogens, which, as mentioned before, possess molecular structures recognized by invariant pattern recognition receptors of the innate defense mechanisms (1).

VI.

T-CELL-DEPENDENT SUPPRESSION

Evidence has steadily been mounting for the tolerogenic importance of some type of Tcell-dependent suppression of potentially autoaggressive T cells (29). The idea of suppressor T cells was first suggested in 1974 by Gershon (30), but the failure to isolate a distinct subset of suppressor T cells has led many to question their existence (31). Nevertheless, one way in which T cells can suppress immune response is by the inhibitory effects of cytokines. The release of TGF-β by T cells after some forms of antigen stimulation is one example (32). Furthermore, the evidence obtained by Mosmann and Coffman (33) for two types of helper T cells, Th1 and Th2 with distinct antagonistic lymphokine profiles


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Figure 6 Two subsets of Th cells, with distinct patterns of cytokine production, have been identified: Th1 and Th2. Through their production of IL4 and IL10, the Th2 cells may interfere with the helper function of Th1 cells. Other cytokines, such as γ -interferon (IFN-γ) (e.g., synthesized by CD8 T cells) can enhance (⫹) or diminish (⫺) the activities of Th1 and Th2 cells, respectively. (Fig. 6), strongly suggests that T-cell-dependent immunoregulation of immune responses is a reality that needs further exploration at both cellular and molecular levels. VII.

TOLERANCE IN B CELLS

There are many ways in which T-cell tolerance or lack of T-cell responses to self antigens can be achieved. What happens in the case of self-reactive B cells that may be circulating? The production of high-affinity antibodies of the IgG class is known to be T-cell dependent (34). Such antibodies are usually responsible for tissue damage associated with autoimmune disease. For this reason, and since the threshold of tolerance for T cells is lower than for B cells (35), the lack of self-reactivity in the B-cell repertoire is most likely to result simply from the absence of T-cell help (36,37), the self-reactive helper T cells having been subjected to tolerance induction by one of the mechanisms discussed above (Fig. 7). Nevertheless circumstances do exist in which B cells may become self-reactive. For example, exposure to antigens derived from micro-organisms, expressing both foreign Tcell epitopes and B-cell epitopes cross-reacting with self antigens, will result in a vigorous antibody response (38) (Fig. 8). Furthermore, in contrast to the TCR, the Ig receptor on mature, antigenically stimulated B cells has been shown to undergo hypermutation (39), which could lead to antiself reactivity. Mechanisms inducing tolerance in B cells must thus operate both during their development and following antigenic stimulation in secondary lymphoid tissues (40).

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Figure 7 Self-reactive B cells may in many cases simply fail to react because of the absence of T-cell help, the self-reactive Th cells having been deleted intrathymically. Experiments in transgenic models indicated that, with the caveat concerning the tolerance threshold (35), tolerance mechanisms operating in the B-cell lineage are similar to those for T cells. Thus, encounter of B cells with multivalent cell-membrane-associated self antigens, able to crosslink the Ig receptors on these cells, led to their deletion from secondary lymphoid tissues. This type of tolerance occurred with self antigens, irrespective of whether they were expressed on cells located within the bone marrow or elsewhere. On the other hand, self-reactive B cells exposed to oligovalent, soluble antigen, giving a receptor occupancy of 25%–30%, were not deleted immediately from secondary lymphoid tissues and became anergic. The anergic state was associated with persistent downregulation of the membrane IgM receptor, a failure to upregulate the B7 complex, and death of the B cells within 3–4 days in the T-cell zone, where they had migrated in search of Tcell help. Thus anergic B cells did not persist for significant periods of time after antigenic stimulation (41). However, they could be rescued if given a strong T-cell-help stimulus within 24 h of antigen, once again pointing to the decision between activation and tolerance in B cells being largely T-cell dependent. No evidence for the presence of suppressor T cells or of anti-idiotypic B cells was found in these transgenic models.


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Figure 8 Self-reactive B cells may be able to respond to self-antigenic determinants if the antigens bear foreign T-cell epitopes and self B-cell epitopes. Mechanisms must therefore exist to induce B-cell tolerance as discussed in the text.

ACKNOWLEDGMENTS I am grateful to Professor A. Basten and to Dr. M. Lenardo for useful suggestions and comments.

REFERENCES 1. Medzhitov R, Janeway C. Innate immune recognition: mechanisms and pathways. Immunol Rev 2000; 173:89–97. 2. Burnet FM, Fenner F. The Production of Antibodies. London: MacMillan, 1948. 3. Billingham RE, Brent L, Medawar PB. Actively acquired tolerance of foreign cells. Nature 1953; 172:603–606. 4. Burnet FM. The Clonal Selection Theory of Acquired Immunity. Cambridge, UK: Cambridge University Press, 1959. 5. Lederberg J. Genes and antibodies. Science 1959; 129:1649–1653. 6. Nossal GJV. The immunological response of foetal mice to influenza virus. Austr J Exp Biol Med Sci 1957; 35:549–557.

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7. Dresser DW, Mitchison NA. The mechanism of immunological paralysis. Adv Immunol 1968; 8:129–181. 8. Roelants GE, Goodman JW. Tolerance induction by an apparently non-immunogenic molecule. Nature 1970; 227:175–176. 9. Sprent J, Miller JFAP. Interaction of thymus lymphocytes with histoincompatible cells. I. Quantitation of the proliferative response of thymus cells. Cell Immunol 1972; 3:361–384. 10. Miller JFAP. Immunological function of the thymus. Lancet 1961; 2:748–749. 11. Miller JFAP. Effect of neonatal thymectomy on the immunological responsiveness of the mouse. Proc R Soc London 1962; 156B:410–428. 12. Jameson SC, Hogquist KA, Bevan MJ. Positive selection of thymocytes. Annu Rev Immunol 1995; 13:93–126. 13. Sprent J, Webb SR. Intrathymic and extrathymic deletion of T cells. Curr Opin Immunol 1995; 7:196–205. 14. Goldrath AW, Bevan MJ. Selecting and maintaining a diverse T-cell repertoire. Nature 1999; 402:255–262. 15. Miller JFAP, Heath WR. Self-ignorance in the peripheral T cell pool. Immunol Rev 1993; 133:131–150. 16. Moskophidis D, Lechner F, Pircher H, Zinkernagel RM. Virus persistence in acutely infected immunocompetent mice by exhaustion of antiviral cytotoxic effector T cells. Nature 1993; 362:758–761. 17. Miller JFAP, Kurts C, Allison J, Kosaka H, Carbone FR, Heath WR. CD8 T cell activation by cross-presentation of self antigens. Immunol Rev 1998; 165:267–277. 18. Mackay CR, Marston WL, Dudler L. Naive and memory T cells show distinct pathways of lymphocyte recirculation. J Exp Med 1990; 171:801–817. 19. Lenardo M, Chan KM, Hornung F, McFarland H, Siegel R, Wang J, Zheng L. Mature T lymphocyte apoptosis—immune regulation in a dynamic and unpredictable antigenic environment. Annu Rev Immunol 1999; 17:221–253. 20. Wang J, Zheng L, Lobito A, Chan KM, Dale J, Sneller M, Yao X, Puck JM, Straus SE, Lenardo MJ. Inherited human caspase 10 mutations underlie defective lymphocyte and dendritic cell apoptosis in autoimmune lymphoproliferative syndrome type II. Cell 1999; 98:47–58. 21. Ingulli E, Mondino A, Khoruts A, Jenkins MK. In vivo detection of dendritic cell antigen presentation to CD4⫹ T cells. J Exp Med 1997; 185:2133–2141. 22. Bretscher PA, Cohn M. A theory of self–nonself discrimination respectively. Science 1970; 169:1042–1049. 23. Lafferty KJ, Prowse SJ, Simeonovic CJ, Warren HS. Immunobiology of tissue transplantation: a return to the passenger leukocyte concept. Annu Rev Immunol 1983; 1:143–173. 24. Matzinger P. Tolerance, danger and the extended family. Annu Rev Immunol 1994; 12:991– 1045. 25. Solinger AM, Ultee ME, Margoliash E, Schwartz RH. T-lymphocyte response to cytochrome c. I. Demonstration of a T-cell heteroclitic proliferative response and identification of a topographic antigenic determinant on pigeon cytochrome c whose immune recognition requires two complementing major histocompatibility complex-linked immune response genes. J Exp Med 1979; 150:830–848. 26. Brent L, Medawar PB, Sparrow EM. Quantitative studies on tissue transplantation immunity. I. The survival times of skin homografts exchanged between members of different inbred strains of mice. Proc R Soc London 1954; 143B:43–58. 27. Billingham RE, Brent L, Medawar PB. Quantitative studies on tissue transplantation immunity. III. Actively acquired tolerance. Phil Trans R Soc London 1956; 239B:357–412. 28. Vance RE. Cutting edge commentary: A Copernican revolution? Doubts about the danger theory. J Immunol 2000; 165:1725–1728. 29. Saoudi A, Seddon B, Heath V, Fowell D, Mason D. The physiological role of regulatory T


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cells in the prevention of autoimmunity: the function of the thymus in the generation of the regulatory T cell subset. Immunol Rev 1996; 149:195–216. Gershon, RK. T-cell control of antibody production. Contemp Topics Immunobiol 1974; 3: 1–40. Moller G. Do suppressor T cells exist? Scand J Immunol 1988; 27:247–250. Kehrl JH, Wakefield LM, Roberts AB, Jakowlew S, Alvarez-Mon M, Derynck R, Sporn MB, Fauci AS. Production of transforming growth factor β by human T lymphocytes and its potential role in the regulation of T cell growth. J Exp Med 1986; 163:1037–1050. Mosmann TR, Coffman RL. Heterogeneity of cytokine secretion patterns and functions of helper T cells. Adv Immunol 1989; 46:111–147. Miller JFAP. Lymphocyte interactions in antibody responses. Int Rev Cytol 1972; 33:77–130. Rajewsky K. The carrier effect and cellular cooperation in the induction of antibodies. Proc R Soc London 1971; 176B:385–392. Miller JFAP. The First Burnet Lecture: the thymus in immunity. Rec Austral Acad Sci 1971; 2:82–98. Harris DE, Cairns L, Rosen FS, Borel Y. A natural model of immunologic tolerance. Tolerance to murine C5 is mediated by T cells and antigen is required to maintain unresponsiveness. J Exp Med 1982; 156:567–584. Goodnow CC, Adelstein S, Basten A. The need for central and peripheral tolerance in the B cell repertoire. Science 1990; 145:1373–1379. Berek C, Milstein C. The dynamic nature of the antibody repertoire. Immunol Rev 1988; 105: 5–26. Goodnow CC, Cyster JG, Hatley SB, Bell SE, Cooke MP, Healy JI, Akkaraju S, Rathmell JC, Pogue SL, Shokat KP. Self-tolerance checkpoints in B lymphocyte development. Adv Immunol 1995; 59:279–368. Fulcher DA, Lyons AB, Korn SL, Cook MC, Koleda C, Parish C, Fazekas de St Groth B, Basten A. The fate of self-reactive B-cells depends primarily on the degree of antigen receptor engagement and availability of T-cell help. J Exp Med 1996; 183:2313–2328.

8 Role of Inflammatory Mediators in Autoimmune Disease JOHANNES M. VAN NOORT TNO Prevention and Health, Leiden, The Netherlands

I.

INTRODUCTION

In the development of T-cell-mediated autoimmune disease, inflammatory mediators are essential and they play roles that are essentially the same as in all other immune-mediated processes. Apart from providing signals that trigger innate (and usually local) antimicrobial responses, they are also crucial to set the scene for autoreactive T lymphocytes to become activated. To appreciate this latter aspect, it is important to understand how inflammatory mediators influence the activation of T cells in general. The activation of T cells requires clustering of a wide range of highly specialized molecules on the surface as well as on the inside of a T cell to form a supramolecular complex for productive interaction with antigen-presenting cells (APC) (1,2). Short molecules form the center of this supramolecular complex, and include the T-cell receptor (TCR)–CD3 complex and, for example, protein kinase C. Longer molecules such as integrins and CD45 are positioned on the outer rim of the complex. At the same time, surface rafts are formed that functionally link molecules of the TCR complex with intracellular signaling molecules, allowing interactions at the surface of the T cell to be translated into intracellular activation signals that regulate gene expression. On the surface of the APC, complementary ligands must be present to interact with the several different components of the supramolecular surface complex on T cells, not just with the TCR alone. A functional synapse depends crucially on multiple interactions between different pairs of ligands. Only then can antigen trigger a specific response by T cells. The main ligand molecule on the surface of APC is the major histocompatibility complex (MHC) molecule, which presents the antigen. Additional ligands include socalled costimulatory molecules such as CD40, CD80, and CD86, and several adhesion 65

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molecules including intercellular adhesion molecule-1 and vascular cell adhesion molecule-1. Soluble mediators such as interleukin (IL)-12 that can be produced by APC also play a major role in multimolecular interactions between APC and T cells (3). Together, the nature of all signals and their duration will be integrated by T cells and translated into a comprehensive response (4,5). Of crucial importance is the fact that APC do not express the costimulatory sets of ligands required by T cells in a constitutive manner. Almost all costimulatory molecules are inducible and produced only by the APC when it first receives specific signals to do so (6,7). These signals are given by proinflammatory mediators. Essentially, these mediators provide a signal to APC that homeostasis is disrupted, infection or stress occurs, and that a specific immune response may be in order. As a consequence, APC set the scene for T cells to probe the site. MHC molecules are upregulated, phagocytic activity of APC is stimulated to sample the antigenic microenvironment, surface ligands appear for engagement of supramolecular TCR complexes, and soluble mediators and chemotactic gradients are formed to recruit T cells actively and prepare them for activation. These elements together not only control whether or not T cells can become activated at all but they also play important roles in determining the quality of the ensuing specific immune response. By secreting IL-12, for example, APC can polarize specific immune responses into predominantly proinflammatory type-1 responses. Very complex interactions determine whether or not an APC will direct T cells into type 1, type 2, or downregulatory responses (3). Apart from activating APC, as sentinels that translate changes in their microenvironment into molecular signals for T cells, inflammatory mediators can also directly interact with T cells and influence their function. Thus, inflammatory mediators control autoimmune responses at various levels and via interactions with different cell types. The molecular mechanisms involved are highly complex and are only beginning to be unraveled. Inflammatory mediators include mediators such as cytokines, chemokines, lipids, hormones, and low-molecular-weight (toxic) chemicals; physicochemical parameters including temperature, osmolarity, radiation, and pH; and a whole range of microbial products. These mediators or conditions activate intracellular signaling pathways that integrate the inflammatory signals and regulate gene transcription, enzyme cascades, and structural reorganizations within cells. The wide range of inflammatory mediators precludes their comprehensive discussion in a single chapter. In this chapter, I have limited myself to discussing three elements in the story of how inflammatory mediators affect (auto)immune responses. First, the recently discovered toll-like receptors will be discussed. These receptors form part of an ancient defense system against microbial pathogens and specifically recognize microbial molecules alien to the mammalian body. Thus, the discovery of toll-like receptors essentially redefines a wide range of microbial molecules as bona fide inflammatory mediators. Understanding the role of these receptors, and the consequence of their engagement, sheds new light on mechanisms via which microbial pathogens can influence the development of (auto)immune responses. Toll-like receptors represent a completely new level of immune responsiveness to pathogens, in addition to the well-known level of specific immune responses mediated by T and B cells. Next, the p38 mitogen-activated protein kinase (MAPK) pathway is reviewed, which is one of the major intracellular regulatory pathways activated by inflammatory mediators, including those that act via the above-mentioned toll-like receptors. This review is primarily intended to highlight the complexity of intracellular mechanisms that translate the signals given by inflammatory

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mediators into changes in gene expression. To some extent, members of the p38 MAPK pathway may be regarded as inflammatory mediators themselves, and they have recently attracted much attention as novel targets for selective anti-inflammatory drugs. Finally, the role of stress proteins (or heat-shock proteins) in autoimmune disease will be discussed. Stress proteins have been under investigation for a long time as potential antigenic triggers for autoimmune disease. Yet novel data reveal that stress proteins can also act as inflammatory mediators, independent from any specific T- or B-cell response. They can, for example, engage toll-like receptors and directly activate inflammatory responses. Again, however, the level of differentiation in such mechanisms is high and no uniform rules apply. II. TOLL-LIKE RECEPTORS Over the past 3 years, remarkable progress has been made in our understanding of how microbial pathogens can influence (auto)immune responses. Previously, attempts to understand the well-recognized impact of viruses or bacteria on autoimmune disease were primarily focused on specific immune reactivity. Structural similarities between pathogens and self proteins, for example, have been exhaustively examined for their potential to induce cross-reactive responses and, thus, to influence autoimmune disease. It has now become clear, however, that pathogens can also influence autoimmune reactions at a completely different level. This level includes activation of specific sets of receptors designed to detect the presence of microbial structures. In insects such as Drosophila, no specific immune system exists but innate responses allow the production of antimicrobial peptides. In 1996, it was found that certain Drosophila receptors important for embryonic development also control the production of such antimicrobial peptides and that these receptors were activated by microbial structures, or by the products of proteolytic pathways activated by pathogens (8,9). The first receptor of this kind to be identified was termed ‘‘toll,’’ German slang for ‘‘great’’ or ‘‘far out.’’ Key to the ability of the toll receptor to control antimicrobial responses in Drosophila is its intracellular domain, which is strikingly homologous to the intracellular portion of the mammalian IL-1 receptor (IL-1R). Thus, the question arose whether perhaps specific receptors for microbial products also exist in mammals. Indeed, the first human toll-like receptor was discovered in 1997 (10). Several toll-like receptors (TLRs) have since been identified and found to be essential components of the innate immune response in vertebrates (11–13). For example, both in mice and humans, TLRs participate as key receptors in the response against bacterial endotoxins (14). It has now become clear that TLRs represent a family of homologous proteins characterized by an extracellular leucine-rich repeat domain and a cytoplasmic domain responsible for intracellular signaling. This intracellular IL-1R-like domain binds to the protein myeloid differentiation factor-88 (MyD-88) that links TLRs to downstream signaling pathways similar to those involved in IL-1 signaling, involving the IL-1R-associated kinase (IRAK) (15,16). Downstream, IRAK activation by TLRs primarily triggers activation of NF-κB, which induces expression of molecules such as interferons α and β, IL-1, IL-6, IL-8, and also CD80, an essential costimulatory molecule for the onset of specific T-cell responses (17). Since MyD-88 can also link TLRs to the Fas-associated death domain (FADD) and caspase-8 activation pathways, TLR signaling can also lead to the induction of apoptosis (18). Although NF-κB activation appears to be a major consequence of TLR signaling, activation of other signaling pathways may also occur, for example, of the p38

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MAPK pathway (17), which is discussed in more detail below. Overall, the highly conserved IL-1R signaling route employed by toll-like receptors in both insects and mammals probably reflects the ancient evolutionary roots of this signaling pathway in the response to microbial pathogens (19). Ligand recognition by the presently known TLRs is the subject of continuing research. In a general sense, it has been proposed that the extracellular domain of TLRs recognize so-called pathogen-associated molecular patterns (PAMPs). These PAMPs include a wide variety of structures typical for microbial pathogens and absent from mammalian cells. These include bacterial cell-wall components such as lipopolysaccharides (LPSs), peptidoglycans and teichoic acids, N-formylated peptides that do not exist in

Figure 1 The role of toll-like receptors in innate immune responses. Human cells express a variety of toll-like receptors (TLR) with differential affinities for typically bacterial and viral structures as well as for self-stress proteins. The structures recognized by TLRs are commonly referred to as pathogen-associated molecular patterns. The intracellular signaling domain of TLRs is very similar to that of the IL-1-receptor and consequently triggers similar intracellular signaling cascades. Dependent on the cell type involved and the status of that cell, TLR signaling can lead to a wide variety of proinflammatory signals, and even to apoptosis. Thus, TLRs serve as sensors for the presence of unusual structures in the body, and their engagement often provokes immune surveillance. The dominant IL-1-like signaling route is indicated here but, depending on the cell type involved, significant links exist between TLRs and other intracellular signaling pathways.


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mammals, DNA sequences typical of bacterial (CpG-DNA), and microbial carbohydrates. As such, TLRs function as sensors for the presence of potentially pathogenic microbial structures. In addition to microbial structures, TLRs can also recognize self-structures that are abnormally modified or expressed as the consequence of stress, damage, or disease. Recognition of the body’s own stress proteins, for example, reflects this function of TLRs. By triggering innate immune responses, TLRs induce immediate antimicrobial responses and, in a more general sense, prepare the site for local activation of specific immune responses by T cells. This seems to be an appropriate response when microbial infection occurs or when the tissue is stressed, damaged, or diseased by some other cause. Although TLRs generally appear to perform their sensor function on the surface of cells, they may also probe structures within phagosomes of macrophages and monocytes in which extracellular molecules, including microbial structures, are taken up. For TLR-2, this specific way of operating has recently been described (20). Figure 1, shows a schematic overview of TLR function in innate immune responses. It is not unreasonable to expect that in the near future more TLRs will be identified, polymorphisms will emerge, and much more will become clear of the specific ligand recognition patterns of these TLRs. III. p38 MITOGEN-ACTIVATED PROTEIN KINASE The human genome encodes more than a thousand protein kinases. These enzymes phosphorylate a wide range of targets, making up as much as 30% of all cellular proteins in eukaryotic cells. Many inflammatory mediators including cytokines and growth factors, bacterial products, and physicochemical stress activate intracellular MAPK cascades. These cascades consist of tiered signaling molecules, each phosphorylating and thereby activating another downstream mediator. They culminate in the activation of transcription factors that regulate gene expression by direct binding to specific DNA sequences (21– 23). MAPK family members are characterized by a protein loop that contains two sites for phosphorylation in a common threonine-x-tyrosine motif. Dual-specificity MAPK kinases (MKKs) are responsible for their phosphorylation at both sites and these MKKs are in turn activated by other upstream kinases in the cascade, termed MKK kinases (MKKKs). At the same time, sets of specific phosphatases are active in rapidly and selectively removing phosphate groups from activated kinases, thus regulating their activity. This strategy allows the cell to respond rapidly to signals, often within minutes, without having to synthesize or degrade entire protein molecules. Although MAPK signaling cascades are still not fully mapped, three major and one minor pathway have been defined to date. The major ones are referred to as the epidermal growth factor-regulated kinase (ERK) pathway, the c-Jun N-terminal kinase (JNK) pathway, and the p38 MAPK pathway. Their activation affects the function of several transcriptional factors notably activator protein-1 (AP-1), the nuclear factor of activated T cells (NFAT), and members of the signal transducer and activator of transcription (STAT) family, which are intimately involved in cytokine regulation. Activation of MAPK pathways has been repeatedly documented in conditions of inflammation (22). For example, the activation of p38 MAPK, a pathway typical for higher eukaryotes, has been documented to lead to production of proinflammatory cytokines such as IL1-β and tumor necrosis factor alpha (TNF-α); chemokines such as monocyte chemotactic protein-1; enzymes involved in inflammation and remodeling such as inducible nitric oxide synthase, cyclo-

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oxygenases, and collagenases; and adhesion molecules including vascular cell adhesion molecule-1. Like other MAPK pathways, the p38 MAPK pathway is activated by a variety of triggers including stress, UV light, osmotic shock, engagement of toll-like receptors, and certain proinflammatory cytokines such as IL-1β and TNF-α (24,25). As a typical stress-activated kinase, p38 MAPK is known to be involved in a wide range of cellular functions including growth, development and differentiation, apoptosis and migration, but a large part of p38 MAPK functions certainly also has an impact on inflammatory processes, cytokine production, and leukocyte recruitment and migration. In order to understand p38 MAPK functions, it is important to realize that there are, in fact, several different isoforms of p38. The four known p38 MAPK isoforms, α, β2, γ, and δ, are structurally similar, but not identical (26,27). Each of these isoforms is expressed at different levels in different types of cells, they respond to different triggers, and they are sensitive to different inhibitors (28). The major p38α isoform, for example, is highly expressed in leukocytes and endothelial cells; the γ isoform is only found at high levels in skeletal muscle (26,29); and the δ isoform is primarily found in lung, kidney, testis, pancreas, and small intestine (28). The ability of upstream MKKs to activate p38 MAPKs is different for each of the isoforms. For example, p38 MAPKα can be phosphorylated by MKK-3, -4, and -6, but p38 β2 is preferentially phosphorylated by MEK-6 and cannot be activated by MKK-3 (30,31). A range of different phosphatases exist for the selective inactivation of p38 MAPK (32,33). Every different type of cell may have its own p38 MAPK and phosphatase profile and therefore respond in its own individual way to defined stimuli (22). In neutrophils, for example, TNF-α activates p38 MAPKα and δ, whereas LPS leads to the selective activation of p38δ (34). Phorbol esters instead lead to the preferential phosphorylation of ERK1/2 and not p38 MAPKs (21). In other cells, this situation may very well be different again. Also in vivo, defined forms of stress trigger markedly different p38 activation profiles in the different cell types present in one organ (35). A variety of signals converge in the p38 MAPK pathway, and a variety of possible activation cascades diverge again downstream of p38 (36). The predominant flow of activation via selective phosphorylation is determined in part by levels of regulatory ‘‘chemostats’’ inside cells, which are members of other signaling cascades that modulate the MAPK cascade. Ceramide is a well-known example of a substance that has a substantial impact on the activation flow in MAPK-signaling cascades (37). Ceramide can promote MAPK-regulated growth and differentiation in some cells, while it stimulates MAPKinduced apoptosis in others. ‘‘Chemostats’’ such as ceramide determine to a large part the exact way that specific signals flow through signaling cascades and, thus, the exact way in which individual signals are translated into changes in gene expression. This complexity renders it very difficult to compile a generally applicable list of potential triggers for each of the MAPK family members. Each time, not only the trigger but also the responding type of cell (and even its developmental stage) must be defined. Table 1 shows some of the triggers that have been described for activation of p38 MAPKs in different cell types. (The examples are derived from a more complete summary given in Ref. 22.) The notion that specific kinases control inflammatory signals has inspired a search for specific inhibitors for members of the MAPK cascades. Such inhibitors could potentially be useful as anti-inflammatory agents and in autoimmune diseases. A series of pyridinyl imidazole compounds has been identified that are very specific and effective inhibitors of p38 MAPK. Both in vitro and in vivo such inhibitors reduce cytokine production and have been found effective in reducing the severity of experimental autoimmune disease in animal models (38). Side effects such as hepatotoxicity, however, have so far precluded applica-


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Table 1 Examples of Inflammatory Mediators That Trigger p38 MAPK Activation Type of stimulus Pathogen-associated structures S. aureus Lipopeptides Mycoplasma proteins Echovirus-1 Clostridium toxin Cytokines TNF-α IL-1 IL-2 IL-7 IL-17 IL-18 Growth factors TGF-β GM-CSF IGF Physicochemical stress Heat shock Stretch UV light Arsenite Other mediators CD40 cross-linking Norepinephrine Carbachol Okadaic acid Collagen

Recipient cell type

Cellular response

Leukocytes Macrophages Leukocytes Cell lines Cell lines

H2O2 production IL-1, TNF-α production IL-8 production junB expression c-Jun expression

Neutrophils, chondrocytes Cell lines Cell lines Cell lines Chondrocytes Cell lines

Apoptosis Not determined Proliferation Proliferation iNOS, COX-2 production IL-8 production

Neutrophils Mast cells Cell lines

Actin reorganization Developmental regulation Antiapoptosis response

HeLa cells Myocytes Cell lines Cell lines

Unknown Hypertrophy Unknown ERK activation

B-cell line PC12 cell line Muscle cell Fibroblasts Dermal fibroblasts

ICAM expression Differentiation hsp phosphorylation MMP-1 expression MMP-13 expression

tion of MAPK inhibitors in humans. The development of MAPK inhibitors as novel antiinflammatory agents, however, will no doubt continue.

IV.

STRESS PROTEINS

Stress proteins (or heat shock proteins [HSP]) are a remarkable group of proteins whose expression can be rapidly modulated under the influence of a variety of triggers. Stress proteins are generally grouped into families of similar molecular mass. The families of 60 kDa (HSP60), 70 kDa (HSP70), and 90 kDa (HSP90) stress proteins are the best studied (39,40). Much less is known about the smaller stress proteins with molecular masses between 20 and 27 kDa (HSP27) (41). Most stress proteins share the property of being upregulated in many types of cells in response to elevated temperatures (hence the term ‘‘heat shock proteins’’). Although this may perhaps suggest a common regulatory pathway for stress proteins, they are in fact regulated by highly differentiated signaling cascades that are usually different from one cell type to another. Most stress proteins perform housekeeping functions under normal conditions and are expressed in a constitutive man-

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ner in almost all cells. HSP60 and HSP70, for example, play important roles in normal protein biosynthesis and intracellular protein trafficking. Small stress proteins appear to have important functions in maintaining the integrity and motility of cytoskeletal elements, which may explain why several small stress proteins are not present in prokaryotes. For some time, stress proteins have been implicated in the development of autoimmune disease (40,42). The remarkable immunogenicity of some stress proteins, combined with the fact that they readily accumulate in diseased tissues, fueled interest in stress proteins as potential autoimmune targets in human diseases such as rheumatoid arthritis, diabetes, and multiple sclerosis. This idea was originally supported by the observation that adjuvant-induced arthritis in rats was primarily mediated by responses against the mycobacterial HSP60 included in the adjuvant. It was believed that cross-reactivity between the mycobacterial HSP60 in the adjuvant and the rat’s own HSP60 was the major factor that led to the precipitation of autoimmune disease (39). Subsequent studies, however, have revealed that the relationship between anti-HSP60 responses and autoimmunity are not that simple. Contrary to the original expectations, evidence has accumulated that anti-HSP60 T-cell responses are more likely involved in the downregulation of specific autoimmune responses than in stimulating them. HSP60 immunization protects animals from the subsequent development of experimentally induced autoimmune disease in several different models (43,44) T cells from both mice and autoimmune patients also appear to respond to self-HSP60, primarily by producing downregulatory cytokines such as IL-4 and IL-10, rather than by secreting proinflammatory cytokines such as interferon-γ (45,46). A downregulatory response by T cells to HSP60 certainly makes sense in the light of the fact that it is a true self-antigen that is constitutively expressed in lymphoid organs. Such a condition usually tolerizes the immune system by leading to deletion from the immune repertoire of strongly reactive T cells and selecting for regulatory qualities in mildly reactive ones. The regulatory quality of the T-cell response to HSP60 therefore meets this expectation but innate responses to HSP60 do not. Several reports have documented that an encounter with HSP60 (or HSP70) protein triggers several different types of cells to mount an innate response involving the production of proinflammatory factors. Mouse or human macrophages, as well as endothelial or smooth muscle cells, respond to HSP60 by upregulating the expression of adhesion molecules and the release of proinflammatory mediators including IL-6, IL-12, IL-15, and TNF-α (47,48). It was recently discovered that HSP60 mediates these effects by binding to the toll-like receptor-4 and/or CD14, the LPS receptor, which is often closely linked to TLRs (49,50). In human macrophages, HSP60 stimulation via CD14 or TLRs leads to activation of the p38 MAPK pathway, the consequences of which are discussed above. These findings reveal that HSP60 must not only be considered as a self-antigen for specific autoimmune T-cell responses but also as a truly inflammatory mediator itself. It is still unclear what controls the balance between proinflammatory innate responses to HSP60 and regulatory adaptive responses. Both factors may play a role in responses to other HSP as well, but the balance may be different for each HSP. Tissue distribution of HSP and individual regulatory pathways is of crucial importance. Recent data for the small stress protein alpha B-crystallin highlight the impact of tissue distribution on the nature and quality of adaptive anti-HSP immune responses. In humans, alpha B-crystallin is restricted in its expression to a limited number of tissues and, most importantly, it is not expressed in any lymphoid organ under normal conditions (51). Because the human immune system is not tolerized for self-alpha B-crystallin, it is potentially


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Figure 2 Stress proteins not only represent self antigens for specific autoimmune responses but also act as inflammatory mediators that directly trigger innate immune responses. Stress proteins have been under investigation for a long time as important self antigens in autoimmunity. Primarily dependent on whether or not stress proteins are constitutively expressed in lymphoid organs, the specific immune repertoire may or may not be tolerant for self stress proteins. In the case of heat-shock protein 60 (HSP60), constitutive lymphoid expression renders the specific immune repertoire of vertebrates functionally tolerant for the protein. Uptake of HSP60 by routine phagocytosis by an APC will lead to presentation of HSP60-derived antigenic determinants to T cells via the trimolecular complex of major histocompatibility complex molecules (MHC), processed antigen (Ag), and the T-cell receptor (TCR). An ensuing specific T-cell response by the tolerized immune system will largely lead to a regulatory response, characterized by the production of cytokines such as IL-4 and IL-10. In the case of the small stress protein alpha B-crystallin (αB), the exceptional situation exists in humans that this protein is absent from lymphoid organs. Not being tolerant, a specific immune response to self-alpha B-crystallin in humans is proinflammatory, leading to secretion of large amounts of IFN-γ. In addition to these specific immune responses, both stress proteins are likely to provoke proinflammatory innate immune responses since they can also directly interact with TLR on the surface of APC. In the case of HSP60, the aggregate of innate and specific immune responses includes both pro- and anti-inflammatory components. The response to alpha B-crystallin tends to be uniformly directed toward proinflammatory responses.

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highly responsive to the protein. For this reason alpha B-crystallin, which sometimes accumulates at high levels in central nervous system myelin, is currently under investigation as a potential trigger for autoimmune responses in multiple sclerosis (52,53). The potential responsiveness of the human immune system against alpha B-crystallin is activated when viral infections occur. Under such conditions, alpha B-crystallin appears in lymphoid cells concomitant with the pathogen, and a strong proinflammatory autoimmune response against the protein is mounted (51). Other mammals show a radically different tissue distribution of alpha B-crystallin. In normal rodents and primates, alpha B-crystallin is constitutively expressed in all lymphoid tissues (as is the case for most HSP) and, consequently, immune tolerance exists (54–56). No T-cell or antibody responses are triggered when the animals are immunized with self-alpha B-crystallin. In humans, alpha B-crystallin can act as a potent proinflammatory factor in specific autoimmune responses, but it fails to do so in other mammals. Recent data indicate that alpha B-crystallin, like HSP60, can also induce direct innate responses. In humans, the innate response to alpha B-crystallin appears to amplify the adaptive immune response: both are proinflammatory. Microglia cells, for example, produce elevated levels of nitric oxide and TNF-α in response to exposure in vitro to the small HSP (57). It is unknown what mechanism mediates innate responses to alpha B-crystallin. Whether or not these also involve signaling via toll-like receptors remains to be established. The above two examples again illustrate the complexity and diversity of both adaptive and innate immune responses to HSP (Fig. 2). Adaptive immune responses may be regulatory, or proinflammatory, dependent on the nature of the HSP and the species. Innate responses to HSP also exist and, to date, only proinflammatory innate responses have been documented. Much is still to be learned about the role that HSP may play in autoimmune diseases as either general inflammatory mediators for innate responses or as antigenic targets of specific autoimmunity.

V.

CONCLUDING REMARKS

Recent developments in the field of inflammatory mediators have started to uncover the dazzling complexity of the collection of molecules and mechanisms involved in inflammation and innate immune responses. Not long ago, inflammation and stress were widely perceived as conditions that would activate signaling pathways and production of certain molecules in a fairly uniform and straightforward manner. It is now becoming increasingly clear that every individual type of cell responds in its own way to inflammatory mediators and that myriad molecules and pathways are involved in translating the precise type of stress or inflammatory signal into a well-defined individualized cellular response. The levels of complexity and differentiation in these processes are much higher than was once imagined. Sometimes a single inflammatory mediator can trigger one type of cell to proliferate while leading another type of cell into apoptosis. Novel inflammatory mediators are emerging, such as microbial molecules and stress proteins that can be added to the already impressive list of different inflammatory mediators. This growing complexity certainly poses new challenges to our understanding of autoimmune diseases and the impact of microbial infection on their development. Yet, the more complex the mechanisms of inflammation turn out to be, the more options may emerge for intervention using selective anti-inflammatory agents, to the ultimate benefit of patients with autoimmune disorders.


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ACKNOWLEDGMENTS These studies were supported by the Dutch Foundation for the support of MS Research. The authors are grateful to Drs. K. Havenith and J.M. te Koppele for critical reading of the manuscript.

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9 Role of Cytokines in Autoimmune Disease LUBA LOPATINSKAYA, NATASHA NIKOLAEVA, and LEX NAGELKERKEN TNO Prevention and Health, Leiden, The Netherlands

I.

INTRODUCTION

In the late 1970s it became clear that lymphocytes and macrophages mediate a wide variety of actions through the secretion of soluble proteins with hormonal activity. These factors were initially found in crude supernatants of cell cultures include growth factors, lymphokines, interferons, and interleukins and are referred to as cytokines. Subsequent expression of recombinant cytokines allowed a more accurate analysis of their biochemical characteristics and functional properties. Nevertheless, the role of many cytokines in vivo still remains obscure due to the fact that their activities are often pleiotropic in nature and frequently shared with other cytokines. As far as the regulation of the immune response is concerned, much progress has been achieved inspired by the pioneer work of Mosmann and Coffman (1), who showed in the mouse that unique immunological effector functions can be attributed to distinct CD4 T cell subsets characterized by unique cytokine profiles. Th1 cells are particularly involved in cell-mediated immunity by the secretion of interferon-γ (IFN-γ) and lymphotoxin, whereas humoral immunity is largely regulated by Th2 cells that secrete interleukin (IL)-4 and IL-10. During the last decade additional subsets such as Th3 (2) and Tr1 cells (3) have been identified that contribute to the maintenance of tolerance by the secretion of cytokines such as IL-10 and transforming-growth-factor-β (TGF-β). These T-cell subsets differentiate from naive CD4 T cells in response to peptides presented by MHC class II positive antigen-presenting cells. Various cytokines have been identified as key factors that determine the development of T-helper cells (4) and in particular IL-12 (5) has received much attention because it strongly polarizes towards Th1 responses. IL-18 has 79

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Figure 1 T-cell subsets, cytokines, and autoimmune diseases.

been identified as a cytokine that acts in synergy with IL-12 by upregulation of IL-12 receptor β2 subunits (6). T-helper subsets and the cytokines they produce play a major role in a wide variety of immunological diseases. Given the fact that Th1 and Th2 cells mutually inhibit each other’s activities, it is generally thought that an imbalance between Th1 and Th2 cells may result in a decreased threshold facilitating loss of tolerance to selfpeptides and the subsequent development of autoimmune disease (Fig. 1). Various experimental autoimmune diseases, such as experimental autoimmune encephalomyelitis (EAE), experimental autoimmune thyroid disease, and collagen-induced arthritis, but also the spontaneous development of insulin-dependent diabetes mellitus (IDDM) in nonobese diabetic mice (7) are considered to include a pathogenic role of autoreactive Th1 cells. On the other hand, autoimmune diseases that demonstrate a strong involvement of autoantibodies are considered to be associated with an increased activity of Th2 cells. These considerations are taken into account in the development of intervention strategies based on the modulation of cytokines. However, as discussed below, treatment of experimental autoimmune disease employing neutralizing antibodies and studying disease models in cytokine knock-out mice have shown that selective targeting of cytokines might be ineffective or even harmful. II. LESSONS FROM ANIMAL MODELS The vast majority of studies concerning the role of cytokines and regulatory mechanisms have been performed in EAE, a model for multiple sclerosis. The advantage of this model is that disease can be induced by peripheral sensitization of T cells with defined myelin peptides, and that the pathology is confined to the central nervous system. The induction of EAE requires the presence of Freunds’ complete adjuvant, most likely because the Mycobacterium component strongly induces the Th1-polarizing cytokine IL-12. The dis-

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ease is dependent on autoreactive Th1 cells and can be transferred by such cells to naive recipients. Th1 cells recruited to the central nervous system in response to locally secreted chemokines become involved in the activation of macrophages, which in turn are responsible for the destruction of oligodendrocytes and myelin by the secretion of proteolytic enzymes and release of reactive oxygen intermediates. This process results in the loss of nerve conduction and paralytic symptoms. Full consensus with regard to the precise role of individual cytokines in EAE has not yet been reached in view of many contradictory findings. Unexpected was that neutralization of IFN-γ with specific antibodies—aimed to limit the activity of Th1 cells—was found to exacerbate EAE (8). On the other hand, IL-4 (which is regarded as a Th2-derived anti-inflammatory cytokine) was found both to improve (9) and aggravate the severity of EAE (10). Moreover, myelin basic proteinspecific Th2 cells appeared to have the potential to induce EAE rather than providing for protection (11). These unexpected findings may be explained by the fact that these cytokines may have a broad spectrum of activities and may play different roles during different stages of the disease. Recent studies have demonstrated that the effect of IL-12, which is regarded as one of the key factors in the development of Th1-mediated autoimmunity, is highly dependent on the timeframe of treatment and apparently on the stage of the disease. In experimental autoimmune uveitis and in experimental autoimmune thyroiditis, both regarded as Th1mediated diseases, IL-12 may even be protective (12,13).

III. AUTOIMMUNITY IN CYTOKINE KNOCK-OUT MICE Tumor-necrosis-factor-α (TNF-α) is presumed to play an important role as a cytokine in the effector phase of inflammatory responses. Indeed, neutralizing antibodies block much of its deleterious effects in EAE (14). Nevertheless, this cytokine might play a dual role: TNF knock-out mice immunized with myelin–oligodendrocyte glycoprotein develop more severe EAE than wild-type mice, suggesting that TNF may also limit the extent of the inflammatory response in the central nervous system (15). Although an important role has been attributed to IFN-γ as one the major products of Th1 cells, early experiments have shown that anti-IFN-γ antibodies exacerbate EAE. The use of IFN-γ and IFN-γ receptor knockouts made clear that IFN-γ can suppress the severity of disease in EAE (16,17) and collagen-induced arthritis (18,19). Accordingly, although initial studies suggested that Th2 cells may control the activity of EAE by the secretion of IL-4, IL-4 knockouts do not show an increased severity of EAE (20), suggesting that the potential of this cytokine as a therapeutic may have been overestimated. After the identification of IL-12 as a bridge between innate and adaptive immunity and a key factor in Th1-mediated responses, many studies have provided evidence for an important role for this cytokine in autoimmunity as well. Because IL-12 is strongly inhibited by IL-10, it has been postulated that an IL-10/IL-12 immunoregulatory circuit determines the development of autoimmunity (21). Early studies showed inhibition of EAE (22) and collagen-induced arthritis (23) by anti-IL-12 antibodies or by IL-10 (10). IL-10deficient mice develop more severe EAE (21,24) whereas IL-10 transgenic mice are resistant (25). IL-10-deficient mice are also more sensitive to colitis than wild-type mice and this sensitivity is abrogated by anti-IL-12 not by anti-IFN-γ (26). On the other hand, IL12-deficient mice are resistant to EAE; IFN-γ-deficient mice are sensitive to EAE unless treated with anti-IL-12 (21).

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Although increasing evidence supports a major role for a proper balance between IL-10 and IL-12 in the development and progression of autoimmune disease, the exact roles of these cytokines still need further attention. IV.

CYTOKINES IN HUMAN AUTOIMMUNE DISEASE

Whereas animal models provide evidence (although sometimes conflicting) for the importance of a proper Th1/Th2 balance in the control of autoimmunity, the situation is less clear in humans. This is due in part to the fact that the availability of pathological material is mostly limited and consequently many studies are performed employing peripheral blood. Lack of consensus can thus in part be due to the fact that cytokine levels in body fluids do not always give the right impression of local autoimmune processes. Indeed, it is often difficult to find a correlation between continuing inflammatory processes in tissues, cytokine levels in body fluids, or cytokine production by circulating immunocompetent cells. Moreover, clinical trials aimed at the neutralization of harmful cytokines may sometimes be associated with unexpected, severe side effects. A.

TNF-␣

TNF-α is considered to be one of the most important cytokines involved in the pathology of many autoimmune diseases. Genetic studies have identified several TNF-region markers that are associated with susceptibility to rheumatoid arthritis (RA) and the severity of the disease (27). TNF-α levels are increased in plasma, synovial fluid, and rheumatoid joint tissues of such patients. TNF-α receptors are simultaneously expressed by synoviocytes, thereby suggesting a pathogenic role for TNF-α in cartilage destruction (28). TNF-α levels in blood are also correlated with the severity of RA and joint destruction (29). In view of its deleterious effects, clinical trials have been designed aiming at the neutralization of this cytokine. Two agents for neutralizing TNF-α are currently available: humanized anti-TNF antibodies and soluble human TNF receptors. Randomized phase II and III clinical trials with these anti-TNF reagents have demonstrated an acceptable safety profile and marked clinical efficacy in cases of RA that have not responded adequately to conventional therapy (30). Whether anti-TNF therapy also protects joints from structural damage is under investigation. A pathogenic role for TNF-α has also been demonstrated in Crohn’s disease; antiTNF therapy was reported to have beneficial effects in moderate to severe disease, although some side effects were observed (31,32). The role of TNF-α in multiple sclerosis (MS) is less certain. The expression of TNF-α and its receptors is increased in acute MS lesions (33). Likewise, increased TNF-α mRNA expression has been found both in peripheral blood mononuclear cells (PBMC) and cells derived from cerebrospinal fluid (34,35). Moreover, increased levels of this cytokine are correlated with the severity and progression of the disease (36). A recombinant TNF receptor p55 immunoglobulin fusion protein has been used in a double-blind, placebo-controlled phase II clinical trial in MS patients to evaluate whether it would reduce the formation of new lesions. However, treatment failed to be beneficial: treated patients experienced more exacerbations than placebo controls (37). These contradictory observations might be explained by assuming a local beneficial role for TNF-α, as has been suggested by studies in EAE (16). An involvement of TNF-α has particularly been found in the pathogenesis of autoimmune diseases with a proinflammatory compound, such as those mentioned above: IDDM and autoimmune


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thyroiditis. However, it might have some impact as well on Th2-mediated disease like myasthenia gravis (MG) or disease presumed to have both a Th1 and Th2 involvement such as systemic lupus erythematosus (SLE). B.

IFN-␥ and IL-12

These two cytokines are regarded as representative for Th1-mediated immune responses and they may play an early role in the pathogenesis of many autoimmune diseases. For instance, IFN-γ polymorphisms are associated with susceptibility to IDDM (38), whereas increased expression of IFN-γ has been found in MS, RA, and IDDM. Evidence for a harmful role for IFN-γ in MS comes from an early trial employing this cytokine as an antiviral agent for the treatment of MS; this trial had to be interrupted in view of serious aggravation of the disease (39). This, however, supports the idea that MS is largely Th1mediated. Much attention has recently focused on IL-12, a heterodimer including p35 and p40 subunits, which are encoded by unrelated genes and regulated separately. RA patients show an increased expression of IL-12p40 mRNA and an increased production of both IL-12p70 and IL-12p40 by synovial fluid mononuclear cells and PBMC, compared to healthy controls; levels of IL-12 reflect disease activity in these patients (40). In Crohn’s disease, lamina propria mononuclear cells show an increased capacity to release bioactive IL-12 (41), whereas such cells are rare or undetectable in patients with noninflammatory gut disorders. Increased expression of IL-12p40 mRNA has also been found in acute MS plaques (42). Furthermore, the IL-12p40 subunit is strongly increased in cerebrospinal fluid and serum of MS patients with a progressive course of the disease (43). A longitudinal study by our group has demonstrated that PBMC of MS patients express increased levels of IL12p40 mRNA during the development of active lesions; these increased levels precede the clinical relapses (44). Altogether, cumulative data show that in particular IL-12 is an important determinant of Th1-mediated autoimmunity. As discussed below, experimental trials employing recombinant IL-10 largely support this idea. An imbalance between IL-12 and IL-10 may also play a role in SLE. PBMC from SLE patients produce low levels of IL-12p40 in response to polysaccharides, which correlates negatively with disease activity (45). Dependent on the disease stage, serum levels of IL-12 may be increased in these patients (46). C.

IL-10

As an endogenous inhibitor of IL-12, low levels of IL-10 are considered to be unfavorable for Th1-mediated autoimmune diseases. Evidence has been obtained that these diseases are associated with impaired IL-10 production and an exaggerated production of proinflammatory cytokines. A decreased expression of IL-10 mRNA has been demonstrated in MS patients compared with controls; this decrease is even more pronounced in secondary progressive MS (44). The remission phase of the disease appears to be associated with increased IL-10 mRNA levels (47). A significant negative correlation between IL-10 production and clinical activity is also found in RA (48). IL-10 inhibits the antigen-presenting capacity of synovial macrophages, even when they are efficiently activated, which further emphasizes the anti-inflammatory potential of IL-10 in RA (49). IL-10 is a potent inhibitor of proinflammatory

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cytokines, and is one of the candidate therapeutics for Th1-mediated diseases. However, initial clinical trials employing IL-10 in RA are not encouraging: unfortunately, so far no clinical improvement was achieved by treatment with different IL-10 dosages. Microscopic analysis of synovial tissue revealed no significant change in the extent of infiltration by inflammatory cells or the expression of cytokines in response to treatment (50). Whereas IL-10 may have the potential to control Th1-mediated disease, it is suggested to promote Th2-mediated autoimmunity. IL-10 is involved in the pathogenesis of pemphigus vulgaris and bullous pemphigoid, which are both considered to be driven by Th2-cytokines. Blister fluid from patients with bullous pemphigoid contains elevated amounts of IL-10 (51). Serum levels of IL-10 are increased during the active stage of pemphigus vulgaris and correlate with increased titers of autoantibodies and disease severity. IL-10 is also increased in patients with Sjo¨gren’s syndrome, in whom it may account for the overproduction of autoantibodies (52). Unexpectedly, IL-10 is more frequently increased in the incomplete (possible) form of Sjo¨gren’s syndrome than the complete (definite) form. Therefore, elevated IL-10 levels may either characterize an early stage of exocrine dysfunction or may be upregulated to contribute to limiting the severity of disease (53). PBMC of patients with SLE and their first-degree relatives show increased numbers of cells that spontaneously produce IL-10. Moreover, cells have higher basal and induced IL-10 levels (54). This supports the hypothesis that IL-10 production may be genetically determined and predisposes toward the development of SLE. High innate IL-10 production underlies susceptibility for SLE, but not the severity of the disease (55). The first studies employing IL-10 antagonists in SLE patients show that such a treatment may be beneficial in the management of refractory SLE and underline the involvement of IL-10 in the pathogenesis of this disease (56,57). D.

IL-4 and IL-13

IL-4 and IL-13 are two closely related Th2 cytokines, which share a common receptor component. Both inhibit the production of proinflammatory cytokines and chemokines by monocytes and promote human B-cell proliferation and activation. These cytokines are deficient in most of the Th1-driven diseases and overexpressed in Th2-type autoimmunity triggering aggravation of the diseases. PBMC from IDDM patients have a decreased capacity of IL-4 production in comparison to healthy controls (58). Moreover, a downregulated production of IL-4 combined with a normal Th1-type cytokine secretion has been found in prediabetic humans, suggesting that the early stage of the autoimmune process in type-I diabetes in humans is associated with decreased function of Th2 cells rather than overactivation of Th1 cells (59). In RA, the levels of IL-4 and IL-13 are low both in synovial fluid and peripheral blood (60), whereas the expression of IL-4 mRNA in synovial fluid mononuclear cells and PBMC from these patients is below the detection level. The expression of IL-4 mRNA is almost absent from cerebrospinal fluid derived cells in MS patients (35). However, MS lesions show an increased expression of IL-4 mRNA by microglial cells and astrocytes and this possibly reflects an attempt to control the inflammatory response (61). The immunomodulatory properties of IL-4, in particular its potential to polarize Thelper-cell responses to a Th2 phenotype, suggest that it may be of benefit in the treatment of Th1-mediated autoimmune diseases. Indeed, in several autoimmune models IL-4 was


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shown to have inhibitory effects. Both the systemic administration of IL-4 and transgene expression of IL-4 in β-cells of the islets of Langerhans prevent the onset of diabetes in NOD mice (62). In adjuvant arthritis intra-articular retroviral gene treatment results in a significant reduction in paw swelling; moreover, treatment resulted in decreased bone destruction, as evidenced by x-ray (63). The therapeutic use of IL-4 in humans has been limited, in part due to dose-limiting side effects observed in clinical human trials. IL-4 together with IL-10 is currently being tested for the local liposome-mediated gene transfer in patients with severe IBD of the rectum. Local administration of cytokines has the advantage that it avoids systemic toxic side effects and is not associated with systemic inhibition of proinflammatory cytokines. Moreover, it allows for increased local concentrations over a prolonged period of time (64). Recently, it has also been demonstrated that gene therapydelivered IL-13 decreases the production of proinflammatory cytokines by synovial fluid mononuclear cells in humans, suggesting its therapeutic potential in the treatment of RA patients (65). Although IL-4 and IL-13 may be of benefit for Th1-mediated diseases, they appear to promote the progression of Th2-mediated autoimmune diseases. Perilesional skin biopsies from patients with bullous pemphigoid are characterized by the deposition of IL-4 and IL-13, which are relevant in the recruitment and adhesion of eosinophils within the dermal infiltrates. Thus these cytokines may play a role in the pathogenesis of blister formation in these patients (66). V. CYTOKINES IN GRAVES’ OPHTHALMOPATHY Although the pathology of Graves’ ophthalmopathy (GO) comprises the involvement of thyroid-specific antibodies that specifically bind to, or cross-react with, antigens of retroorbital tissues, an important local role for cytokines is increasingly appreciated (67,68). Locally produced cytokines, derived from infiltrating T cells or from the tissue itself, are responsible for the enhanced expression of MHC molecules, heat shock proteins and adhesion molecules in retro-orbital fibroblasts, adipocytes, myocytes, and endothelial cells. Infiltrating retro-orbital T cells from GO patients recognize autologous retro-orbital fibroblasts in an MHC-class I restricted manner. On the other hand, eye muscle and retroorbital fat tissue are also considered as two major targets of the autoreactive response, based on evidence that lymphocyte infiltration in these tissues is a prominent histological feature of GO (69). There are contradictory data about the exact role that cytokines play in GO. Some authors consider GO to be Th1-dependent, some Th2-mediated, whereas other data suggest the involvement of both Th1 and Th2 cytokines in the pathogenesis of this disease (70). In orbital tissues of GO patients a variety of proinflammatory cytokines has been found (71), either in frozen sections or in primary cultures of orbital fibroblasts. However, the cytokine expression pattern varies in time, which may reflect the course of the disease. The few available studies performed in a limited number of patients suggest a Th1 cytokine profile in the early stages, whereas Th2 cytokines might be involved in the progression of the disease (72). It has recently been shown that Th1 cytokines are mainly found in eye muscle tissue, whereas Th2-cytokines are detected mostly in orbital fat tissue. Moreover, a correlation between the expression of IL-6 mRNA and the orbital volume has been demonstrated (69). These results suggest that both Th1-like and Th2like immune responses may play a role in the development of ophthalmopathy. Accordingly, both Th1 and Th2 cytokines are increased in the serum of GO patients (70). However, cultures of PBMC from patients with GO produce significantly less IL-12 and significantly more IL-10 and IL-4 than PBMC cultures from healthy controls (64). This

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suggests a Th2-bias in GO patients; however, it should be taken into account that the cells responsible for the pathology have migrated from the periphery into the target organ. VI.

CONCLUDING REMARKS

Many studies in experimental mouse models have pointed to a pivotal role of certain cytokines in the pathogenesis of autoimmune diseases. However, although cytokinedeficient mice have illustrated that certain cytokines are key to the pathogenesis of autoimmunity, they have also made clear that redundancy exists that may limit the success of targeted therapy. Moreover, many cytokines are pleiotropic in nature and may display disease-inhibiting as well as disease-promoting activities dependent on the stage of the disease. As a consequence, selective treatment with cytokines or their antagonists may result in a shift from Th1-associated to Th2-associated pathology and vice versa. It is uncertain to what extent evidence from (inbred) animal models can be extrapolated to the clinical situation. Nevertheless, several human autoimmune diseases show a Th1-biased cytokine profile, whereas others show a Th2-biased cytokine profile, although this may depend on the stage/progression of the disease. Altogether, there is ample evidence that certain cytokines do not only reflect the pathogenesis of autoimmune disease but can also act as targets for therapy, provided that harmful side effects are eliminated. ACKNOWLEDGMENTS Dr. Lopatinskaya is supported by grant 940-33-047 from the Dutch Organization for Scientific Research. Dr. Nikolaeva is supported by a Du-Pre´ fellowship from the International Federation of Multiple Sclerosis Societies. REFERENCES 1. Mosmann TR, Coffman RL. TH1 and TH2 cells: different patterns of lymphokine secretion lead to different functional properties. Annu Rev Immunol 1989; 7:145–173. 2. Fukaura H, Kent SC, Pietrusewicz MJ, Khoury SJ, Weiner HL, Hafler DA. Induction of circulating myelin basic protein and proteolipid protein-specific transforming growth factor-beta 1-secreting Th3 T cells by oral administration of myelin in multiple sclerosis patients. J Clin Invest 1996; 98:70–77. 3. Groux H, Ogarra A, Bigler M, Rouleau M, Antonenko S, Devries JE, Roncarolo NG. A CD4 (⫹) T-cell subset inhibits antigen-specific T-cell responses and prevents colitis. Nature 1997; 389:737–742. 4. Ogarra A. Cytokines induce the development of functionally heterogeneous T helper cell subsets. Immunity 1998; 8:275–283. 5. Trinchieri G. Interleukin-12: a proinflammatory cytokine with immunoregulatory functions that bridge innate resistance and antigen-specific adaptive immunity. Annu Rev Immunol 1995; 13:251–276. 6. Chang JT, Segal BM, Nakanishi K, Okamura H, Shevach EM. The costimulatory effect of IL-18 on the induction of antigen-specific IFN-gamma production by resting T cells is IL-12 dependent and is mediated by up-regulation of the IL-12 receptor beta2 subunit. Eur J Immunol 2000; 30(4):1113–1119. 7. Wong FS, Dittel BN, Janeway CAJ. Transgenes and knockout mutations in animal models of type-1 diabetes and multiple sclerosis. Immunol Rev 1999; 169:93–104. 8. Heremans H, Dillen C, Groenen M, Martens E, Billiau A. Chronic relapsing experimental


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10 Role of Adhesion Molecules in Autoimmune Disease ROBERT W. McMURRAY University of Mississippi Medical Center and G.V. (Sonny) Montgomery VA Hospital, Jackson, Mississippi, U.S.A.

I.

OVERVIEW

The interaction of endothelial and tissue-based adhesion molecules with their respective ligands on circulating mononuclear cells mediates their adherence to sites of inflammation. Adhesion molecules also regulate leukocyte circulation, lymphoid tissue homing, endothelial accumulation, transendothelial migration, and persistence of effector cells in the extracellular matrix. These adhesive interactions, at several levels and due to various causes, mediate sequestration and persistence of inflammatory cells and their associated cytokines to immune and autoimmune sites of inflammation. Conversely, modulation or blockade of these molecules appears to ameliorate autoimmune disease, particularly in experimental models. Modulation of adhesive forces include, but are likely not limited to, changes in adhesion molecule avidity with activation, cytokine stimulation, surface expression and density, progression of temporal expression, and circulating soluble ligands (1,2). Adhesion molecules are currently classified into three major groups: selectins, integrins, and immunoglobulin supergene family (IGSF) members. These respective classifications are also relevant to a chronological hierarchy in response to inflammatory mediators in inducing leukocyte adhesion to an inflammatory site. In general, selectins mediate transient early slowing and ‘‘rolling’’ of intravascular leukocytes, integrins form stronger adhesive molecules and facilitate transendothelial migration, and integrin interaction with IGSF adhesion molecules mediates localization and persistence of inflammatory effector cells. This chapter summarizes the classification of these molecules and their ligands, the factors known to mediate their expression, their role in thyroid autoimmune disease, especially Graves’ disease, and their potential for targets of immunotherapy. A glossary of terms for the novice is provided in Table 1. 91

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Table 1 Glossary of Terms Adhesion molecule A cell surface protein that functions in leukocyte circulation, migration, attachment, or signal transduction. α (alpha) 4 The alpha chain component of the heterodimeric integrin molecule with the number designation ‘‘4’’ as opposed to other distinct alpha chains (e.g., α4β7 as VLA-4); other distinct α chains include α5, α6, αL, and αM. Avidity Adhering strength. Extracellular matrix (ECM) Loose milieu of glycoproteins and mucopolysaccharides (e.g., fibronectin and laminin) suspending and supporting cells and tissue structure. Heterodimer A molecule consisting of two different chain structures joined together. Immunoglobulin supergene family (IGSF) A family of cell surface molecules whose structural motifs are similar to that of immunoglobulin chains. Integrin An adhesion receptor with a heterodimeric structure that binds to counterreceptors or extracellular matrix. ICAM-1—Intercellular adhesion molecule-1 An IGSF adhesion molecule that binds LFA-1. LFA-1—Lymphocyte function antigen An integrin adhesion receptor that binds ICAM-1. Ligand The binding partner of a specified molecule. Selectin An adhesion receptor with an N-terminal lectin-binding structure. Soluble adhesion receptor An adhesion receptor that is solubilized in fluids such as serum or cerebrospinal fluid. VLA-4—Very late antigen 4 An integrin adhesion molecule receptor that binds to VCAM-1 or extracellular matrix. VCAM-1—Vascular cell adhesion molecule-1 An IGSF receptor expressed primarily on endothelium binding VLA-4.

II. CLASSIFICATION Selectins are expressed on lymphocytes (L-selectins), platelets (P-selectins), and endothelium (E-selectins) and have the common structural motif of an N-terminal lectin binding domain. Rapid association and disassociation binding to glycosylated and sialylated ligands of the endothelium or extracellular matrix mediates leukocyte ‘‘rolling’’ and localization of leukocytes to inflammatory sites. This function facilitates leukocyte response to additional chemoattractants and cytokines, resulting in upregulation of additional integrin and IGSF adhesion molecules that serve as costimulatory molecules for leukocyte activation as well as transendothelial migration. L-selectin is expressed constitutively on all leukocytes and is critical to leukocyte adherence to peripheral lymph nodes and activated endothelium, through glycosylated molecules, glycam-1, CD34, and MadCAM-1. P-selectin also serves to bind leukocytes to endothelium and induces upregulation of inte-

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grin molecule expression, leading to further adhesive events. E-selectin is upregulated on endothelium by interleukin-1 (IL-1) and tumor necrosis factor (TNF-α) and binds leukocytes to inflamed endothelium through sialylated mucin-like molecules. Adhesive actions of selectin are transient but chronologically essential to the formation of the stronger and more persistent adhesions of integrins and their ligands. Integrin adhesion molecules are heterodimeric (α and β) molecules classified on the basis of their β subunit. Subunit recombination forms different receptors with different binding specificities. Integrins may be identified by a descriptive name (e.g., very late antigen-4 [VLA-4]), heterodimeric combination name (α4β1 ), or cluster designation name (CD49d/CD29). Following initial adhesive actions of selectins, integrins noncovalently bind their respective ligand and lead to transendothelial migration and more cell/cell or cell/extracellular matrix (ECM) interactions. These receptors also ‘‘integrate’’ or transduce extracellular information into the inside of the cell and serve as costimulatory signals, providing a secondary level of stimulation to effector cells. Integrins bind to a variety of extracellular matrix proteins or specific IGSF family members (see Table 2), are crucial to persistence of the inflammatory response, and have been associated with several autoimmune inflammatory diseases. Blockade of these receptors clearly abrogates the resultant damage of effector cells in many experimental autoimmune diseases (1). The most common integrin/ligand pairs are VLA-4/VCAM, LFA-1/ICAM-1 or ICAM-2, α4β7 / MadCAM-1 or VCAM, all of which mediate primarily lymphocyte tissue interactions and progressive inflammatory responses. VLA-4 and LFA-1 are prototypical integrin adhesion molecules and have been found to play crucial proinflammatory adhesive roles in several immune and autoimmune inflammatory responses. Both are expressed on leukocytes, bind to endothelial or target cell IGSF receptors and fibronectin, and are upregulated by activation.

Table 2 Primary Adhesion Molecules and Their Ligands Selectins and ligands L-selectin (Mel-14) Glycosylated molecules, glycam-1, CD34, MadCAM-1 E-selectin (ELAM-1) Sialylated molecules P-selectin P-selectin glycoprotein ligand-1 (PGSL-1) Integrins and ligands β1 integrins VLA-4 (α4β1; CD49d/CD29) VCAM, fibronectin, high endothelial venules Fibronectin VLA-5 (α5β1; CD49e/CD29) VLA-6 (α6β1; CD49f/CD29) Laminin β2 integrins LFA-1 (αLβ2; CD11a/CD18) ICAM-1, ICAM-2 ICAM-1, fibronectin Mac-1 (αMβ2; CD11b/CD18) β7 integrins LPAM-1 (α4β7; CD49d/CD-) MadCAM-1; VCAM Immunoglobulin supergene family (IGSF) ICAM-1 (CD54) LFA-1, mac-1 ICAM-2 (CD102) LFA-1 VCAM (CD106) VLA-4 LFA-2 (CD2) LFA-3 LFA-3 (CD58) LFA-2

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Members of the IGSF of receptors share structural amino acid immunoglobulin-like motifs and serve as ligands to integrin receptors. ICAM-1 and ICAM-2, VCAM, and LFA-2 and LFA-3 are the primary IGSF receptors, with ICAM-1 and VCAM-1 being expressed on a wide variety of cells and found predominantly in inflammatory responses, binding leukocyte LFA-1 and VLA-4, respectively. An additional unclassified adhesion molecule includes CD44, which adheres to hyaluronate in extracellular matrix, serves as a memory T-cell marker, and has a multitude of other functions involved in lymphocyte adherence, activation, and formation of memory responses (1). In summary, selectins, integrins, and IGSF adhesion molecules are expressed by a wide variety of cells. Adhesion molecule expression and changes in avidity, in concert with humoral inflammatory mediators and effector cells, coordinate the initiation, progression, and intensity of a localized inflammatory response. III. REGULATION OF ADHESION MOLECULE EXPRESSION Homeostatic balance between adhesive forces determines leukocyte circulation, homing, and transendothelial migration to inflammatory sites, and persistence of the immune response. Expression of adhesion molecules is essential for cell/endothelial, cell/cell, and cell/extracellular matrix adhesion and their expression may be constitutive, regulated, or both. Cytokines such as TNF-α and IL-1 typically upregulate expression of adhesion molecules; however, adhesion molecule persistence may be dependent upon other cytokines such as interferon-gamma (INF-γ), IL-4, and IL-6, which further induces or prolongs expression (1). Furthermore, activation of cells by cytokines, chemoattractants, or costimulatory molecules upregulates either the expression of adhesion molecules or their avidity for their respective ligands. Additional pathophysiological attractants modulating effector cell adhesion and migration in various immune and autoimmune reactions include, but are likely not limited to, leukotriene B4, C5a, histamine, thrombin, substance P, vasoactive intestinal peptide, calcitonin, and endotoxin. Lack of cytokine or activation stimulation leads to transient adhesion interactions and the effector cells. Adhesion molecules are also found in circulating, soluble forms. Soluble adhesion molecules are elevated and circulate in inflammatory disease, but their pathophysiological or theoretical blockade of adhesive interactions or their subsequent clinical significance have not been clearly established. An additional level of adhesive control likely occurs at the level of cell-specific distribution of receptors (e.g., CD4⫹ vs. CD8⫹ lymphocytes). Hence, regulation of adhesive interactions is a complex orchestration of several cascading events leading to persistence and accumulation of effector cells prior to significant inflammatory response and clinical and disease presentation. Elucidation of the temporal events leading to tissue effects and disease presentation will likely identify pathophysiological targets of therapeutic importance. IV.

ADHESION MOLECULE EXPRESSION IN THYROID AUTOIMMUNITY

The development of autoimmune thyroid disease (AITD) is very complex and appears to involve the expression and adhesive interactions of adhesion molecules. Lymphocytic infiltration of the thyroid gland in autoimmune thyroid disorders requires, as a first step, their attachment to endothelial cells (EC) and, subsequently, their interaction with thyrocytes and extracellular matrix proteins. A number of different ligand molecules have been identified to mediate the interaction between EC and leukocyte subpopulations in AITD.

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Since initiation of a specific immune response also involves antigen-receptor independent interactions between accessory molecules, such as adhesion molecules, the expression of adhesion molecules on thyroid epithelial cells (TEC) has been examined. TEC derived from patients with Graves’ disease expressed ICAM-1 and LFA-3 in vitro after stimulation with recombinant human interferon-γ (IFN-γ) or human tumor necrosis factor-alpha (TNFα). However, TEC from nontoxic goiter could be induced to express ICAM-1, but not LFA-3 under similar conditions. Both ICAM-1 and LFA-3 were highly expressed in vivo in Graves’ disease, but not in nontoxic goiter. These findings suggest that TEC are able to express adhesion molecules and support the concept that adhesion molecules play a role in the TEC-specific immune response in autoimmune thyroiditis (3). In similar studies, examination of thyroid specimens of Graves’ disease (GD) thyroid glands and control thyroid glands demonstrated that patients with GD also had enhanced expression of intercellular adhesion molecule-1 (ICAM-1) on capillary endothelial cells around the thyroid follicles and on postcapillary endothelial cells in lesions with aggregates of mononuclear cells. ICAM-1, LFA-1, and VLA-4 were found on thyroid-infiltrating mononuclear cells. Postcapillary vascular endothelial cells also expressed increased ELAM-1, but not VCAM-1. VCAM-1 and ELAM-1 were, however, detected on the dendritic-like cells in the germinal centers of lymphoid follicle-like areas. No significant expression of these adhesion molecules was detected on normal thyroid glands. These results suggest that the LFA-1/ICAM-1 and ELAM-1 pathways may be responsible for the migration of mononuclear cells into the thyroid glands of patients with GD. Furthermore, the VLA-4/VCAM-1 adhesive interactions may play a critical role in the cellular interactions that lead to the formation of B-memory cells and the excess production of antibodies in Graves’ disease (4). These results are further supported by the finding that in Graves’ disease thyroid samples, infiltrating memory CD4⫹ cells expressed high levels of LFA-1 and LFA-2, but expression levels of VLA-4 and VLA-5 did not differ significantly from controls (5). In a separate study, a high proportion of GD intrathyroidal T lymphocytes expressed increased LFA-1, VLA-1, VLA-4, VLA-5 and integrin receptors compared with peripheral blood T lymphocytes from the same patients. The expression of ICAM-1 was increased in EC from GD thyroids. In addition, an upregulated expression of VCAM-1 was found in EC in GD thyroids. Dendritic cells in thyroid lymphoid follicles were also positive for ICAM-1 and VCAM-1. In addition, most intrathyroidal mononuclear cells expressed the ICAM-3 adhesion molecule. This enhanced expression of ICAM-1 and VCAM-1 by thyroid EC in GD likely reflects their ability to regulate leukocyte trafficking and activation by means of the expression of specific ligand molecules. These data further imply that the LFA-1/ICAM-1, ICAM-3, and VLA-4/VCAM-1 adhesion pathways are relevant in localizing and perpetuating the autoimmune response in GD thyroids (6). The complex chronological and cell-specific nature of adhesion molecule expression and interaction are likely responsible for the development of Graves’ thyroiditis. However, the dynamic progression of this disease remains to be elucidated. V. ADHESION MOLECULES IN GRAVES’ OPHTHALMOPATHY The role of adhesion molecules in GD suggests a similar role in Graves’ ophthalmopathy, although such participation remains to be elucidated. The immunological perspectives of GD opthalmopathy are discussed in subsequent chapters of this book. Nevertheless, the inflammatory process and tissue proliferation within the orbit in GD ophthalmopathy sug-

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gest that adhesion and cell/cell or cell/extracellular matrix interaction are crucial to the pathogenesis of orbital disease. Work described in this book has recently extended our knowledge of the evolution and perpetuation of this orbital immune process, including orbital T-cell repertoires, candidate orbital antigens, potential target and effector cells, and their role in the extrathyroidal manifestations of this autoimmune thyroid disease (7,8). It is possible that adhesion receptors discussed in this chapter are pivotal to GD orbital pathogenesis, but their expression, regulation, and role have not been thoroughly characterized. Immunotherapy of this disorder may involve blockade of cell/cell or cell/extracellular matrix adhesive interactions. For example, immunoglobulin superfamily member VCAM-1, which recognizes VLA-4 integrin, is expressed on all leukocytes except neutrophils. Blockade or inhibition of VCAM-1/VLA-4 interaction is expected to have therapeutic potential in treating various inflammatory disorders and autoimmune diseases since this adhesion pathway has a major influence on eosinophil, lymphocyte, and monocyte trafficking. Strategies currently used to selectively inhibit the VCAM-1/VLA-4 adhesive pathway include soluble VCAM-Ig fusion protein, peptide antagonists, antisense oligonucleotides, natural products, and neutralizing antibodies to VCAM-1 or α4 integrin (9,10). Further characterization of adhesion molecule expression in early Graves’ ophthalmopathy (i.e., prior to the establishment of a chronic process), the development of sensitive diagnostic techniques, and the definition of effective antiadhesive immunotherapy may provide a basis for efficacious intervention in this problematic autoimmune disease. REFERENCES 1. McMurray RW. Adhesion molecules in autoimmune disease. Semin Arthritis Rheum 1996; 25:215–233. 2. Mojcik CF, Shevach EM. Adhesion molecules: a rheumatologic perspective [see comments]. Arthritis Rheum 1997; 40:991–1004. 3. Zheng RQ, Abney ER, Grubeck-Loebenstein B, Dayan C, Maini RN, Feldmann M. Expression of intercellular adhesion molecule-1 and lymphocyte function-associated antigen-3 on human thyroid epithelial cells in Graves’ and Hashimoto’s diseases. J Autoimmunity 1990; 3:727– 736. 4. Nakashima M, Eguchi K, Ida H, Yamashita I, Sakai M, Origuchi T, Kawabe Y, Ishikawa N, Ito K, Nagataki S. The expression of adhesion molecules in thyroid glands from patients with Graves’ disease. Thyroid 1994; 4:19–25. 5. Ishikawa N, Eguchi K, Ueki Y, Nakashima M, Shimada H, Ito K, Nagataki S. Expression of adhesion molecules on infiltrating T cells in thyroid glands from patients with Graves’ disease. Clin Exp Immunol 1993; 94:363–370. 6. Marazuela M, Postigo AA, Acevedo A, Diaz-Gonzalez F, Sanchez-Madrid F, de Landazuri MO. Adhesion molecules from the LFA-1/ICAM-1,3 and VLA-4/VCAM-1 pathways on T lymphocytes and vascular endothelium in Graves’ and Hashimoto’s thyroid glands. Eur J Immunol 1994; 24:2483–2490. 7. Heufelder AE. Retro-orbital autoimmunity. Baillieres Clin Endocrinol Metab 1997; 11:499– 520. 8. Heufelder AE, Spitzweg C. [Pathogenesis of immunogenic hyperthyroidism and endocrine orbitopathy] Pathogenese der immunogenen Hyperthyreose und endokrinen Orbitopathie. Internist (Berl) 1998; 39(6):599–606. 9. Oppenheimer-Marks N, Lipsky PE. Adhesion molecules as targets for the treatment of autoimmune diseases. Clin Immunol Immunopathol 1996; 79:203. 10. Foster CA. VCAM-1/alpha 4-integrin adhesion pathway: therapeutic target for allergic inflammatory disorders. J Allergy Clin Immunol 1996; 98(6 Pt 2):S270–S277.

11 Overview of Graves’ Autoimmune Disease ANTHONY P. WEETMAN University of Sheffield, Sheffield, England

I.

INTRODUCTION

In 1835 Robert Graves described four cases of the disease that would bear his name, recognizing in one of these the ophthalmic complications that form a focus for this volume. Caleb Parry, a friend of Edward Jenner, had described eight cases 10 years previously. Karl von Basedow also has been acclaimed in continental Europe for his later description of the association between exophthalmos and thyrotoxicosis. However, if Graves was perhaps fortunate in achieving eponymous status for his contribution to thyroidology, it should also be recalled that he was also the first to describe Raynaud’s syndrome (1)! Graves’ disease is the most common type of hyperthyroidism, which is the state of excess circulating thyroid hormones (either thyroxine [T4] or triiodothyronine [T3], or both) caused by increased thyroid gland synthesis and secretion of these hormones. Although often used synonymously, hyperthyroidism is not the exact equivalent of thyrotoxicosis, which is simply the state of excess circulating thyroid hormones, irrespective of cause. For example, ingestion of excess thyroid hormone or thyroid tissue results in thyrotoxicosis, but suppression of thyroid gland activity (2). This forms a useful basis for considering the different causes of thyrotoxicosis (Table 1). Depending on iodine intake, Graves’ disease accounts for 56–80% of hyperthyroidism in Europe (3) and is the most common autoimmune disease in the United States (4). The incidence of Graves’ disease is around 0.5 :1000 women/year, and 5–10 times lower in men. The peak age of onset is 40–60 years of age. The fundamental cause of Graves’ disease is the production of autoantibodies that bind to and stimulate the TSH receptor (TSHR). These autoantibodies were first suspected following the demonstration of a ‘‘thyroid stimulator’’ in the serum of Graves’ patients. 97

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Table 1 Causes of Thyrotoxicosis Primary hyperthyroidism

Mechanism

Graves’ disease Toxic multinodular goiter

TSHR stimulating antibodies Activating somatic mutation of TSHR; excess iodine intake with previous goiter Activating somatic mutation of TSHR or Gsα protein Activating germline TSHR mutation Excess iodine intake Excess ectopic thyroid tissue

Toxic adenoma Familial nonautoimmune Jod-Basedow phenomenon Struma ovarii; functioning thyroid metastases Thyrotoxicosis without hyperthyroidism Subacute thyroiditis Silent thyroiditis Thyroid destruction (transient) Thyrotoxicosis factitia Secondary hyperthyroidism TSH-secreting pituitary adenoma Thyroid hormone resistance syndrome Hyperemesis gravidarum and tumors secreting hCG

Viral infection Self-limiting, autoimmune destruction Amiodarone, radiation, infarction Ingestion of excessive thyroid hormone or thyroid tissue Excess TSH stimulation Thyroid hormone receptor mutation (only occasional patients have thyrotoxic features) hCG-mediated stimulation of TSHR

TSH, thyroid stimulating hormone; TSHR, TSH receptor; hCG, human chorionic gonadotrophin.

When injected into mice this ‘‘stimulator’’ induced thyroid hormone released over a much longer time scale than TSH (5). This so-called long-acting thyroid stimulator (LATS) was subsequently shown to be an IgG (6), which provided what is still the best example of type V hypersensitivity: the production of antibodies that activate cell surface receptors (7). TSHR antibodies have proven to be very difficult to study for a number of reasons. They are present at much lower concentrations in serum than other thyroid autoantibodies, making derivation of human monoclonal antibodies problematic (8). Also, their binding to the receptor is extremely conformation-dependent, so that attempts to study their interaction with recombinant TSHR have been difficult. Finally, animal models have only been established in the last few years (9) and information derived from these models is only just beginning to provide fresh insights into the pathogenesis of Graves’ disease. II. PREDISPOSITION Although it is now clear that TSHR stimulating antibodies are the proximal cause of Graves’ disease, it is far less obvious what predisposes certain individuals to the condition. In common with most autoimmune disorders, a combination of genetic and environmental factors is involved, with different relative contributions of each between individuals. Some of these factors, especially the inheritance of certain HLA alleles, are common to several autoimmune disorders, and this largely explains the frequent association of Graves’ disease with other conditions (Table 2). The alternative explanation for these associations is that certain autoantigens have cross-reactive epitopes that trigger a dual autoimmune process. The evidence for this explanation is slim at present (10), although thyroid-associated oph-

Overview of Graves’ Disease

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thalmopathy may be the result of an orbital antigen that is cross-reactive with, rather than identical to, a thyroid autoantigen. The best evidence for a genetic predisposition in Graves’ disease comes from twin studies, which have shown a 20–30% concordance rate in monozygotic twins, a much higher figure than in dizygotic twins that share similar exposure to environmental factors (11). However, this concordance rate implies at best only a modest genetic contribution to Graves’ disease, supported by the relatively low frequency in siblings or other family members. A huge effort has been made to determine the genetic basis for Graves’ disease, largely using population-based association studies that have often lacked sufficient statistical power to confirm genuine associations. Moreover, such studies of candidate genes are capable of detecting only relatively small effects that may have less biological relevance than the kind of effect that might be detected by whole genome screening, or searching for new disease-specific loci. Association studies have confirmed a role for HLA alleles in Graves’ disease, especially the HLA-DR3 specificity in white patients. Other HLA associations outside the DR region in general reflect linkage disequilibrium with HLA-DRB1 alleles rather than any additional and independent effect (12,13). The other confirmed genetic association with Graves’ disease is polymorphism of the CTLA-4 gene (14). The latter is expressed in T cells and downregulates their responses when the B7 costimulatory signal is engaged. The contribution of CTLA-4 polymorphism to susceptibility is somewhat less than HLA and the same polymorphisms are associated with other autoimmune disease, such as type 1 diabetes mellitus. Linkage studies have demonstrated a number of new candidate genetic loci for Graves’ disease (15), but much larger numbers of families need to be studied to determine the exact importance of these loci before exact mapping and identification of the responsible genes will become worthwhile. Other candidate loci continue to be examined and may also yield insights into pathogenesis. One example is the association of Graves’ disease with a polymorphism of the IL-4 gene that encodes a key Th2 cytokine involved in regulating antibody production (16). There does not appear to be a major, consistent genetic predisposition to the development of ophthalmopathy that is separate from that seen in Graves’ thyroid disease, although more work is needed in this regard (17). One of Caleb Parry’s original patients had suffered an accident in the weeks before her diagnosis and, since then, stress has been a leading contender among the environmental factors that could cause Graves’ disease. Recent retrospective surveys have tended to confirm this impression, with major life events and minor hassles both being more frequent in the year prior to disease onset than in matched controls (18–20). Prospective studies would provide more powerful evidence, but are logistically impossible. However, the wellknown effects of stress on the neuroendocrine system, and in turn on the immune system, provide a plausible biological explanation for this association. Smoking weakly predisposes individuals to the development of Graves’ disease but is a major risk factor in the development of ophthalmopathy (21). Whether these two effects are linked by a single adverse action on the immune system is unknown; smoking also has direct effects on the thyroid and, via hypoxia, on fibroblasts (22). An increase in dietary iodine may also precipitate Graves’ disease and once again this is likely to be a complex effect, with both iodine-induced hyperthyroidism (the Jod-Basedow phenomenon) and initiation or exacerbation of the autoimmune process playing roles (23,24). Drugs such as lithium and amiodarone (which contains iodine) have been associated with the development of Graves’ disease. A remarkable frequency of Graves’ disease is

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seen after administration of T-cell monoclonal antibodies in the treatment of multiple sclerosis (25). This may provide an important model in which to study disease development from its earliest stage. The female predominance of Graves’ disease (and other autoimmune disorders) is most likely the result of modulation of the autoimmune response by estrogens and other hormones. These endocrine effects may account for the frequent emergence of Graves’ disease in the year after delivery (26). III. THE AUTOIMMUNE RESPONSE Whatever the combination of predisposing factors, the autoimmune response in Graves’ disease is far more complex than the mere production of TSHR-stimulating antibodies. Many abnormal immunological phenomena have been described and it is often unclear which are primary and how they contribute to pathogenesis. The B-cell response to TSHR is T-cell-dependent and TSHR-reactive T cells have been described in Graves’ disease, although there is no single dominant TSHR epitope that could serve as a target for therapeutic modification (27). As in many autoimmune disorders, T-cell tolerance to TSHR appears incomplete in healthy individuals (28), suggesting the operation of mechanisms in addition to central deletion or anergy in maintaining nonresponsiveness to the receptor. The existence of specific T-suppressor cells, peripheral tolerance through the presentation of TSHR by major histocompatibility complex (MHC) class II molecules in the absence of costimulation, resulting in anergy, and clonal ignorance may all be involved (29,30). In addition to MHC class II molecules, thyroid cells in Graves’ disease express a wide array of immunologically active molecules, including cytokines, adhesion molecules, complement-regulatory proteins, and CD40. These are induced by the lymphocytic infiltrate that characterizes Graves’ disease and other types of autoimmune thyroid disease, via cytokines and sublethal complement activation. It is likely that this intrathyroidal response exacerbates and perpetuates the autoimmune responses (31), resulting in the thyroid being a major site of thyroid autoantibody synthesis, with contributions from the draining lymph nodes and bone marrow (32). Most patients with Graves’ disease have evidence of autoimmunity to other thyroid autoantigens besides the TSHR, including autoantibodies against thyroglobulin (TG), thyroid peroxidase (TPO), and the sodium–iodide symporter. Some patients with Graves’ disease initially present with hypothyroidism or run a fluctuating course between this and hyperthyroidism, most likely due to the presence of autoantibodies to the TSHR that block rather than stimulate (33,34). It is not known why there should sometimes be rapid transit between these two antibody species. However, responses against other thyroid autoantigens may contribute to the clinical picture by modifying the thyroid responsiveness to TSHR-stimulating antibodies, and in particular may account for the late development of permanent hypothyroidism in 10–20% of patients successfully treated with antithyroid drugs. IV.

CLINICAL FEATURES AND DIAGNOSIS

A brief description of the systemic manifestations of Graves’ disease is provided in Table 2. It is helpful to differentiate between the features common to all types of thyrotoxicosis and those specific for Graves’ disease (Table 2). The latter include the presence of ophthalmopathy that can be detected clinically in 50–60% of patients with Graves’ disease, although a much larger proportion have subclinical evidence of disease detectable by orbital


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Table 2 Clinical Features of Graves’ Disease Features of thyrotoxicosis Irritability, dysphoria Heat intolerance, sweating, warm and moist skin Fatigue, weakness, tremor Palpitations, tachycardia, atrial fibrillation in the elderly Weight loss with increased appetite Muscle weakness, myopathy Diarrhea, polyuria Oligomenorrhea, loss of libido, gynecomastia Diffuse hair loss Features of Graves’ disease Diffuse goiter (found in some other types of hyperthyroidism) Ophthalmopathy Dermopathy, especially pretibial myxedema Acropachy Splenomegaly, lymphoid hyperplasia Family or personal history of a related autoimmune disease Autoimmune hypothyroidism Type 1 diabetes mellitus Addison’s disease Vitiligo Pernicious anemia Alopecia areata Celiac disease, dermatitis herpetiformis Myasthenia gravis

imaging or other methods (35,36). A minor degree of lid retraction, 1–2 mm, may occur in any type of hyperthyroidism, secondary to sympathetic overactivity, but the eyelid retraction seen in Graves’ disease is usually more extensive and due to additional pathological changes in the levator palpebrae superioris muscle (37). Establishing the diagnosis is a two-stage process. First one must confirm that the patient with suspicious signs and symptoms is truly thyrotoxic and, second, establish that Graves’ disease, rather than an alternative process (Table 1), is the cause. The presence of primary thyrotoxicosis is usually readily verified by the combination of a suppressed circulating TSH level and elevated free T4 level. Around 2–5% of patients with the earliest stage of any type of hyperthyroidism may have an elevated free T3 but normal free T4 level (T3 toxicosis). Once thyrotoxicosis is confirmed, the diagnosis of Graves’ disease can be made by the presence of eye signs or dermopathy; highly suggestive features include a diffuse goiter on palpation, a strong family or personal history of associated autoimmune disorders (Table 2), and positive circulating TG or TPO antibodies. It would seem most logical to confirm the diagnosis by measuring TSHR-stimulating antibodies, but commercially available assays generally measure only antibody binding to the TSHR and hence will include autoantibodies that have a blocking or neutral effect on the receptor (38). Methods to detect TSHR-stimulating antibodies require bioassays that are not widely available. Improved, second-generation assays for TSH-R-binding antibodies have recently been introduced and their role in diagnosis might increase (39), but at present it is debatable

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whether measurement of these antibodies offers a real diagnostic advantage (40). In contrast, the use of TSHR antibody measurement in predicting the likelihood of neonatal thyrotoxicosis in a pregnant woman with Graves’ disease is now well established (40). Patients with apparent Graves’ disease but no detectable circulating TSHR antibodies are sometimes seen; misdiagnosis, poor assay sensitivity, and exclusively intrathyroidal production of TSHR antibodies could be responsible. The vigor with which other diagnostic tests are pursued generally depends on local practice. In cases of doubt, radionuclide tests, showing high thyroidal uptake of radioiodine isotopes or 99m Tc and a diffuse goiter on scintiscanning, are useful in excluding the diagnosis of toxic nodular goiter or destructive thyroiditis. Perhaps the clearest indication for such testing is in the postpartum period, in which the appearance of thyrotoxicosis could be the result of destructive autoimmune thyroiditis or Graves’ disease (41). V.

RELATIONSHIP TO OPHTHALMOPATHY AND DERMOPATHY

The exact relationship between Graves’ thyroid disease and the extrathyroidal manifestations of eye disease and dermopathy remains unclear—are these separate but closely associated disorders or part of the same spectrum? In favor of the former is the presence of ophthalmopathy without Graves’ disease in up to 10% of cases (35). However, half of these patients have autoimmune hypothyroidism and many of the remainder have more subtle evidence of thyroid disease, such as the presence of thyroid autoantibodies or a goiter (42). It is also clear that Graves’ disease may occur several years after the first manifestations of ophthalmopathy (and vice versa), so that the existence of ophthalmopathy without thyroid disease over a protracted period needs to be demonstrated if one is attempting to confirm the existence of two separate processes. At present, the balance of evidence seems to support the concept of a complex but single spectrum of disease, albeit including thyroid autoimmunity generally rather than Graves’ disease alone. For reasons yet to be established, but possibly related to autoreactivity to the TSHR, patients with Graves’ disease have an almost constant, subclinical ophthalmopathy, whereas autoimmune hypothyroidism is far less commonly associated. We still need to clarify whether some Graves’ patients escape orbital disease totally, because present indirect assessment methods may not be sufficiently sensitive to confirm minor orbital involvement (35,36). Dermopathy is much less common than ophthalmopathy and may be a more general manifestation of the same pathogenic process (43). However, generalized subclinical dermopathy in Graves’ disease does not seem to be present (44). Almost all patients with dermopathy have Graves’ disease plus ophthalmopathy, suggesting a very close relationship with this type of thyroid autoimmunity (45). Thyroid acropachy is the rarest and most extreme extrathyroidal manifestation of Graves’ disease; its pathogenesis is obscure but the condition is strongly linked with the presence of dermopathy. VI.

OVERVIEW OF TREATMENT

Although apparent remission may occur in mild cases of Graves’ disease, the duration of such improvements is uncertain. The mortality from untreated Graves’ disease is 10–30%, with considerable morbidity due to cardiovascular and neuropsychiatric complications as well as osteoporosis. Initial treatment is usually with a thionamide antithyroid drug in


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Europe and Japan, whereas radioiodine (131 I) is generally preferred as first-line treatment in North America (46). Subtotal or near total thyroidectomy is a third alternative, and is particularly useful in patients in whom there is a large goiter or any suspicion of coincidental thyroid malignancy. Age and gender are important determinants of success with any treatment (47). A summary of the main benefits and side effects of these treatments is given in Table 3. Antithyroid drugs cause a fall in TSHR and other thyroid antibody levels, an effect most likely related to an immunomodulatory action on the thyroid cells (48). As a result, permanent remission may occur in up to 50% of patients who receive a course of antithyroid drugs, lower rates being likely in those with large goiters or in areas of high iodine intake. In patients whose condition relapses after drug treatment, radioiodine is usually the treatment of choice. However, some physicians remain cautious about administering radioiodine to children and adolescents, because of the theoretical risks of malignancy, especially of the thyroid (49,50). Caution should also be exercised when radioiodine is given to patients with ophthalmopathy, especially smokers, since there can be worsening of the eye problem (51). Prophylactic corticosteroids, given for a short period immediately after radioiodine, prevent this complication. The management of Graves’ disease in pregnancy requires particular attention, as excessive antithyroid drugs given to the mother can cause fetal hypothyroidism and goiter. The lowest possible dosage of drug, given by the titration regimen, is used to maintain maternal free T4 levels in the upper part of the reference range. The autoimmune process usually ameliorates during pregnancy and antithyroid drugs can often be stopped during

Table 3 Overview of Treatment for Graves’ Disease Medical

Advantage

β-Blockers (e.g., propranolol)

Rapid symptomatic relief

Antithyroid drugs (carbimazole, methimazole, propylthiouracil)

Cure in 30–50%; hypothyroidism avoidable by titrating dose or adding thyroxine (block-replace regimen); useful in pregnancy (by titration regimen) Cure in ⬎80% with one dose; simple outpatient treatment

Radioiodine (131 I)

Thyroidectomy

Cure in ⬎95%; removes large goiter; allows histological assessment of coincidental suspicious nodules

Disadvantage No effect on underlying disease process Sustained risk of relapse; minor common side effects of rash, arthralgia, fever; major rare side effects of agranulocytosis, SLE-like syndrome, hepatitis Contraindicated in pregnancy and breast feeding; may cause worsening of ophthalmopathy; high rate of hypothyroidism; requires precautions according to local radiation protocols High rate of hypothyroidism; complications secondary to anesthetic; hemorrhage, parathyroid damage, and recurrent laryngeal nerve damage

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the last trimester. Close follow-up is needed after delivery, as the mother is at increased risk of relapse during the year after delivery. Also, in the last trimester, the risk of neonatal thyrotoxicosis must be established (40). Although present treatments for Graves’ disease are effective, this is often at the expense of hypothyroidism, and complications can be serious, especially in socioeconomically disadvantaged populations (52). Optimal treatment would restore euthyroidism promptly and permanently, without the need for lifelong follow-up or thyroxine therapy. Future advances in our understanding of the immunopathogenesis of Graves’ disease may make such treatment an attainable goal. REFERENCES 1. Taylor S. Graves of Graves’ disease. J R Coll Phys London 1986; 20:298–300. 2. Cohen III JH, Ingbar SH, Braverman LE. Thyrotoxicosis due to ingestion of excess thyroid hormone. Endocr Rev 1989; 10:113–124. 3. Reinwein D, Benker G, Konig MP, Pinchera A, Schatz H, Schleusener A. The different types of hyperthyroidism in Europe: results of a prospective study of 924 patients. J Endocrinol Invest 1988; 11:193–200. 4. Jacobson DL, Gange SJ, Rose NR, Graham NMH. Epidemiology and estimated population burden of selected autoimmune diseases in the United States. Clin Immunol Immunopathol 1997; 84:223–243. 5. Adams DD, Purves HD. Abnormal responses in the assay of thyrotrophin. Proc Univ Otago Med School 1956; 34:11–12. 6. Kriss JP, Pleshakov V, Chien JR. Isolation and identification of the long-acting thyroid stimulator and its relation to hyperthyroidism and circumscribed pretibial myxoedema. J Clin Endocrinol Metab 1964; 24:1005–1028. 7. Weetman AP. Hypersensitivity: stimulatory (type V). In: Encyclopedia of Life Sciences. London: MacMillan (in press). 8. McLachlan SM, Rapoport B. Editorial: Monoclonal, human autoantibodies to the TSH receptor—the Holy Grail and why are we looking for it? J Clin Endocrinol Metab 1996; 81:3152– 3154. 9. Kohn LD, Shimojo N, Kohno Y, Suzuki K. An animal model of Graves’ disease: understanding the cause of autoimmune hyperthyroidism. Rev Endocr Metab Dis 2000; 1:59–67. 10. Tonacchera M, Cetani F, Costagliola S, Alcalde L, Uibo R, Vassart G, Ludgate M. Mapping thyroid peroxidase epitopes using recombinant protein fragments. Eur J Endocrinol 1995; 132: 53–61. 11. Brix TH, Kyvik KO, Hegedu¨s L. What is the evidence of genetic factors in the etiology of Graves’ disease? A brief review. Thyroid 1998; 8:553–556. 12. Heward JM, Allahabadia A, Daykin J, Carr-Smith J, Daly A, Armitage M, Dodson PM, Sheppard MC, Barnett AH, Franklyn JA, Gough SCL. Linkage disequilibrium between the human leukocyte antigen class II region of the major histocompatibility complex and Graves’ disease: replication using a population case control and family-based study. J Clin Endocrinol Metab 1998; 83:3394–3397. 13. Chen Q-Y, Huang W, She J-X, Baxter F, Volpe´ R, Maclaren NK. HLA-DRB1*08, DRB1*0301, and DRB3*0202 are susceptibility genes for Graves’ disease in North American Caucasians, whereas DRB1*07 is protective. J Clin Endocrinol Metab 1999; 84:3182–3186. 14. Yanagawa T, Hidaka Y, Guimaraes V, Soliman M, DeGroot LJ. CTLA-4 gene polymorphism associated with Graves’ disease in a Caucasian population. J Clin Endocrinol Metab 1995; 80:41–45. 15. Tomer Y, Barbesino G, Greenberg DA, Concepcion E, Davies TF. A new Graves’ diseasesusceptibility locus maps to chromosome 20q11.2. Am J Hum Genet 1998; 63:1749–1756.


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Weetman Uetani M, Nagataki S. Untreated Graves’ disease patients without clinical ophthalmopathy demonstrate a high frequency of extraocular muscle (EOM) enlargement by magnetic resonance. J Clin Endocrinol Metab 1995; 80:2830–2833. Burch HB, Wartofsky L. Graves’ ophthalmopathy: current concepts regarding pathogenesis and management. Endocr Rev 1993; 14:747–793. Small RG. Enlargement of levator palpebrae superioris muscle fibers in Graves’ ophthalmopathy 1989; 96:424–430. Rapoport B, Chazenbalk GD, Jaume JC, McLachlan SM. The thyrotropin (TSH) receptor: interaction with TSH and autoantibodies. Endocr Rev 1998; 19:673–716. Costagliola S, Morgenthaler NG, Hoermann R, Badenhoop K, Struck J, Freitag D, Poertl S, Weglo¨hner W, Hollidt JM, Quadbeck B, Dumont JE, Schumm-Draeger P-M, Bergmann A, Mann K, Vassart G, Usadel K-H. Second generation assay for thyrotropin receptor antibodies has superior diagnostic sensitivity for Graves’ disease. J Clin Endocrinol Metab 1999; 84:90– 97. Davies TF, Roti E, Braverman LE, DeGroot LJ. Thyroid controversy-stimulating antibodies. J Clin Endocrinol Metab 1998; 83:3777–3785. Hall R. Pregnancy and autoimmune endocrine disease. Bailliere’s Clin Endocrinol Metab 1995; 9:137–155. Salvi M, Zhang Z-G, Haegert D, Woo M, Cadarso LL, Wall JR. Patients with endocrine ophthalmopathy not associated with overt thyroid disease have multiple thyroid immunological abnormalities. J Clin Endocrinol Metab 1990; 70:89–94. Heufelder AE. Pathogenesis of Graves’ ophthalmopathy: recent controversies and progress. Eur J Endocrinol 1995; 132:532–541. Peacey SR, Flemming L, Messenger A, Weetman AP. Is Graves’ dermopathy a generalized disorder? Thyroid 1996; 6:1–5. Gleeson H, Kelly W, Toft A, Dickinson J, Kendall-Taylor P, Fleck B, Perros P. Severe thyroid eye disease associated with primary hypothyroidism and thyroid-associated dermopathy. Thyroid 1999; 9:1115–1118. Solomon B, Glinoer D, Lagasse R, Wartofsky L. Current trends in the management of Graves’ disease. J Clin Endocrinol Metab 1990; 70:1518–1524. Allahabadia A, Daykin J, Holder RL, Sheppard MC, Gough SCL, Franklyn JA. Age and gender predict the outcome of treatment for Graves’ hyperthyroidism. J Clin Endocrinol Metab 2000; 85:1038–1042. Weetman AP, Tandon N, Morgan BP. Antithyroid drugs and the release of inflammatory mediators by complement-attacked thyroid cells. Lancet 1992; 340:633–636. Ron E, Doody MM, Becker DV, Brill AB, Curtis RE, Goldman MB, Harris III BSH, Hoffman DA, McConahey WM, Maxon HR, Preston-Martin S, Warshauer ME, Wong L, Boice JD Jr, for the Cooperative Thyrotoxicosis Therapy Follow-up Study Group. Cancer mortality following treatment for adult hyperthyroidism. JAMA 1998; 280:347–355. Rivkees SA, Sklar C, Freemark M. The management of Graves’ disease in children, with special emphasis on radioiodine treatment. J Clin Endocrinol Metab 1998; 83:3767–3776. Bartalena L, Marcocci C, Tanda ML, Manetti L, Dell’Unto E, Bartolomei MP, Nardi M, Martino E, Pinchera A. Cigarette smoking and treatment outcomes in Graves’ ophthalmopathy. Ann Intern Med 1998; 129:632–635. Sherman SI. Clinical and socioeconomic predispositions to complicated thyrotoxicosis: a predictable and preventable syndrome? Am J Med 1996; 101:192–198.

12 Systemic Manifestations of Graves’ Disease WARNER BURCH Duke University Medical Center, Durham, North Carolina, U.S.A.

I.

INTRODUCTION

Graves’ disease has three components: hyperthyroidism, ophthalmopathy, and dermopathy. Hyperthyroidism or thyrotoxicosis, the cardinal manifestation of Graves’ disease, occurs when body tissues are exposed to increased concentrations of tetraiodothyronine (T4) and/or triiodothyronine (T3). The causes of hyperthyroidism include Graves’ disease, thyroiditis, toxic multinodular goiter, toxic thyroid adenoma, exogenous hyperthyroidism (iatrogenic, factitious, iodine-induced), excess thyroid-stimulating hormone (TSH) (trophoblastic tumors, pituitary tumor), and ectopic thyroxine production (struma ovarii and metastatic follicular thyroid carcinoma). Graves’ disease is by far the most common cause of hyperthyroidism, with a female to male ratio of 7 or 8: 1. It is typically a disease of young women (20–40 years), but Graves’ disease may occur in patients at any age. Graves’ disease is identified clinically from other forms of hyperthyroidism by the presence of diffuse thyroid enlargement, ophthalmopathy, and occasionally pretibial myxedema, although all these signs may be absent. Ophthalmopathy is present in 5–20% of patients with recent onset Graves’ disease and may occur before hyperthyroidism (‘‘euthyroid Graves’ disease’’), at the onset of hyperthyroidism (the usual case), or years later after the patient is euthyroid. Hyperthyroidism may affect every organ system. The presentation varies with age; the classic symptoms and signs of hypermetabolism are seen in young and middle-aged patients but less so in the elderly. The degree of hyperthyroidism also varies with the severity of the levels of T4 and T3. There is a strong familial component in Graves’ disease; 50–60% of patients have a positive history of thyroid disease. There is no racial

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predilection for Graves’ disease, although Asian patients are more likely to present with hypokalemic periodic paralysis. The symptoms of hyperthyroidism relate to excessive sympathomimetic activity and increased catabolic activity: nervousness (irritability and emotional labiality), increased perspiration, heat intolerance, palpitations, weight loss, dyspnea, fatigue and weakness, increased appetite, hyperdefecation, menstrual dysfunction, and eye symptoms. Signs of hyperthyroidism include goiter (thyroid enlargement), tremor, hyperkinesis, eye signs (exophthalmos, lid retraction, lid lag), tachycardia (resting rate ⬎90; atrial fibrillation), smooth and velvety skin, moist and warm hands, onycholysis (‘‘Plummer’s nails’’), and thyroid bruit. In the elderly these classic signs are often missing and one sees cardiac problems (heart failure and tachydysrhythmias), weight loss, weakness, or anorexia. The striking absence of the adrenergic and hyperkinetic symptoms is sometimes called apathetic hyperthyroidism. When a patient with hyperthyroidism presents with fever, altered mental status, and acceleration of thyrotoxic signs and symptoms, the clinical diagnosis of thyroid storm is made. This is often precipitated by stress such as surgery, infection, and pneumonia in patients who have previously had undiagnosed hyperthyroidism. The diagnosis of hyperthyroidism is very easy when the clinical disease is obvious. When the signs and symptoms are minimal, the laboratory results are helpful. The serum T4(RIA)/T3U or free T4 levels are usually elevated, as is the serum level of T3 (determined by radioimmunoassay [RIA]). The T3 (RIA) or FT3 is usually elevated to a greater extent than the T4 (RIA) and is sometimes the only abnormal laboratory finding (i.e., T3thyrotoxicosis). Serum TSH levels are suppressed or not measurable (⬍0.05 µU/mL). Hyperthyroidism has generalized effects on various tissues producing numerous abnormal laboratory studies that revert to normal when the hyperthyroidism resolves. Such findings include hypercalcemia, abnormal liver function studies, and increased turnover and degradation of metabolites (e.g., an increase in urinary 17-OHCS, making one suspect Cushing’s syndrome). Subclinical hyperthyroidism diagnosed with low levels of TSH (⬍0.1 µU/ mL with normal free T4 and free T3 levels) on screening chemistry panel is usually asymptomatic. The presenting manifestations of classic Graves’ disease are unmistakable and leave a lasting impression on the examiner. The affected young woman is anxious, nervous, and fidgety: sitting still and keeping hands and feet stationary is nearly impossible. Her speech is quick and generally she is quite talkative. She complains of weakness and fatigue, and generally likes the weight loss and the ability to eat excessively without gaining weight. Palpitations and ‘‘racing heart’’ are easily elicited symptoms, as are heat intolerance and a preference for cooler environs than other people. She often is perspiring and her skin literally radiates heat. Such patients are truly ‘‘wired.’’ Prominence of the eyes, a stare appearance, or diplopia could be symptoms. A friend or relative may notice changes such as goiter or increased nervousness well before the patient does. The history usually reports a 5–20 lb weight loss, but it can be more severe. However, about one in ten thyrotoxic patients actually gain weight because of increased caloric intake in excess of their catabolism. Frequent bowel movements and occasionally frank diarrhea are a concern. On examination, the patient with a classic case demonstrates a diffuse enlargement of the thyroid (goiter). This occurs in over 95% of the patients who present with Graves’ defect (autoimmune process causing hyperthyroidism). On occasion, the goiter may be somewhat nodular. Eye manifestations may vary from normal with minimal eye stare and lidlag, to severe with limitation of extraocular movements, proptosis, and periorbital edema. In the author’s experience, only 5% of the people who initially present with thyro-

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Figure 1 Onycholyses of 4th and 5th digits. Note recession of nail bed.

toxicosis due to Graves’ defect have the infiltrative eye disease. Cardiac bruits are important signs of Graves’ disease, but they are often absent, and thrills are even less common. Both indicate increased blood flow and signify thyrotoxicosis due to overactivity of the thyroid gland. They are not found in other causes of hyperthyroidism such as subacute thyroiditis, toxic adenoma, and multinodular goiter. In patients with Graves’ thyrotoxicosis the skin is warm, moist, and hyperemic, particularly in the hands. Some patients flush easily. The handshake often reveals moist and warm hands. Patients have onycholysis, that is, changes in the nail bed in which the skin separates from the subungual margin leaving a concave margin on the fourth and fifth fingers (see Fig. 1). Onycholysis (Plummer’s nails) is a useful sign of chronic hyperthyroxinemia regardless of cause (seen in other causes of long-standing hyperthyroidism as well). Vitiligo can be found and occasionally some patients report hyperpigmentation. Examination of the lower legs rarely reveals pretibial nonpitting edema, thickening of the skin, accentuation of the hair follicles, and often erythema (Fig. 2a). Pretibial myxedema is uncommon in Graves’ disease and usually occurs in patients with ophthalmopathy and often after the eye disease is stable. Even more uncommon are formation of nodules or tuberous changes (Fig 2b). Other areas of trauma may rarely show the myxedematous changes. The cause of such changes remains unknown. Thyroid acropachy results in clubbing of the fingers with soft tissue changes. Radiographs may show subperiosteal new bone formation. This is also a very rare finding in Graves’ disease. II. ORGAN SYSTEM REVIEW OF HYPERTHYROIDISM As mentioned above, mental and nervous findings vary and are striking. Graves’ disease patients cannot stay still. They often do not sleep well and at times have been found to clean the house at night. Some patients have increased fatigue, fine tremor, and hyperkinetic reflexes. There is occasionally a significant change in personality leading to psychosis. The muscle system is often affected, particularly when these patients lose weight. The weight loss is indiscriminate: fat and muscle loss lead to weakness and fatigue. Facial examination reveals wasting of the temporal muscles and often weakness with an inability to get up from a chair without use of the hands. Occasionally, patients will have concomi-

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Figure 2a Pretibial myxedema. The skin changes extend down on the dorsum of the feet.

Figure 2b

Pretibial myxedema. These changes are an exaggeration of the process in (a) with nodular formation of myxedematous tissue. See the ‘‘tuberous’’ findings on the great toes.

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tant myasthenia gravis. Periodic paralysis is a rare manifestation of hyperthyroidism. In this condition there is a sudden paralysis with hypokalemia, and transport of acid to the cellular tissue leading to profound weakness and paralysis. The paralysis reverses as potassium levels return to normal. The cause of this is unknown, but has an increased frequency among people of Asian origin. The effects from thyroid hormone on the bone lead to increased absorption and calciuria. The changes of the bone are frequent and apparent with longstanding hyperthyroidism. Bone disease may present as a stress fracture. The changes seen on bone DEXA scans have been reported and are generally reversed once the hyperthyroidism has resolved. The cardiovascular changes are due to increased sensitivity to circulating epinephrine and norepinephrine. Palpitations or tachycardia are common symptoms. The pulse is rapid and bounding and systolic blood pressure is often elevated. There is a characteristic wide pulse pressure between diastole and systole. The precordium is often dynamic and bounding in the patient with classical hyperthyroidism. Flow murmurs are often heard. A short, high-pitched murmur in the left second intercostal space has been described in the severely thyrotoxic patient. Premature beats are common. Atrial fibrillation may occur; this may be continuous or paroxysmal. Congestive heart failure is a rare manifestation today. Hyperthyroidism can precipitate stroke and risk of myocardial injury is increased. Beta-blockers produce a dramatic effect on the cardiovascular system in reducing palpitations/increased heart rate and ameliorate sweating and tremor in the symptomatic patient. The changes in the respiratory system are manifested by shortness of breath and dyspnea on exertion. Hematological changes of thyrotoxicosis are generally mild. The hemoglobin and hematocrit are in the lower limits of the normal range because the blood volume is increased. In some patients, there is often lymphocytosis. There may be generalized lymphadenopathy and in about 5% of patients, the spleen tip can be palpitated. Gastrointestinal findings of thyrotoxicosis include increased appetite and weight loss. As mentioned above, there is occasional weight gain with increased caloric intake. Nausea and vomiting are rare except in hyperemesis gravidarum. The transit time for food is decreased and increased frequency of bowel movements is common. The liver may be palpable, especially when there is heart failure. There are occasionally abnormal results of liver function studies including levels of alkaline phosphatase and bilirubin. The reproductive system, particularly in women, is affected by decrease in menstrual flow and shortening or elongation of the menstrual cycle. In men, gynecomastia may develop as a consequence of increased conversion of testosterone to estradiol while they are hyperthyroid. The other endocrine organs including the adrenal cortex have no obvious clinical symptoms. There are measurable changes to the adrenal gland, which are often hypertrophic with increased production of 17-OHCS to match the increased clearance due to hyperthyroidism. It is not uncommon to have elevated ACTH levels with slightly increased pigmentation. Other metabolic effects include increased oxygen consumption. The basal metabolic rate is no longer available. The effects on lipid metabolism have been well recognized and the serum cholesterol level is suppressed. There appears to be increased clearance of cholesterol into bile acids and excretion of bile. Even triglyceride levels are lower.

13 Genetics of Graves’ Disease RATNASINGAM NITHIYANANTHAN and STEPHEN C.L. GOUGH University of Birmingham, Birmingham, England

I.

INTRODUCTION

The principal function of the immune system is to offer protection against the invasion of exogenous antigen. However, at the same time it must also have the ability to recognize self antigen and avoid damage to host tissues. Autoimmune diseases appear to arise, however, as a result of failure of the immune system to recognize self antigen. The common autoimmune disorders collectively affect around 5% of the population, of which the most common are type 1 diabetes, autoimmune thyroid disease, and rheumatoid arthritis. Graves’ disease is an organ-specific autoimmune disease, characterized by the clinical features of thyrotoxicosis and a diffuse goiter with or without ophthalmopathy and dermopathy or myxedema (1). Biochemical features include elevated serum thyroxin levels with suppressed thyroid-stimulating hormone (TSH) levels. Specific antibodies directed against the TSH receptor (TSHR) have been detected in more than 95% of patients with Graves’ disease (2). A primary etiological role for TSHR antibodies is further supported by the development of thyrotoxicosis in neonates born to mothers with Graves’ disease that lasts only for a few weeks until the inhibiting IgG is metabolically cleared to an ineffective concentration (3,4). Biopsies, however, from the thyroid gland in patients with Graves’ disease also show extensive lymphocytic infiltration (1), demonstrating that both antibody- and cell-mediated immune responses are involved in development of the disease process. Graves’ disease affects 0.5–1% of the population in the United Kingdom and commonly presents in the fourth decade of life. There is a strong female-to-male preponderance (5–10:1) (5) and around 50% of patients presenting with Graves’ disease give a family history of thyroid disease (6). A number of factors have been implicated in the etiology 113

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of Graves’ disease including both environmental and genetic components. With respect to environmental effects, a variety of factors have been reported to contribute to the development of Graves’ disease including, for example, dietary iodine intake, infectious agents such as viruses, and stressful life events. Direct evidence of causation for any of these components awaits confirmation. II. GENETIC SUSCEPTIBILITY In support of a genetic component, Graves’ disease tends to cluster in families with an increased risk of thyroid disease in siblings of affected individuals (6). The concordance rate of Graves’ disease has been reported to be between 30 and 50% in monozygotic twins and less than 5% in dizygotic twins (6,7). Brix and his colleagues have recently confirmed these findings in a population-based study of Danish twins (8). They reported a proband wise concordance rate of 35% in monozygotic twins and 7% in dizygotic twins identified from the Danish twin registry. This is undoubtedly one of the most accurate estimates of concordance rates in Graves’ disease. Although starting with over 20,000 twin pairs, meticulous clinical phenotyping of twins on the register discovered only 5 twin pairs being concordant and 40 discordant for Graves’ disease. Higher concordance rates among monozygotic twins who have identical genes compared to dizygotic twins, who have approximately 50% identical genes, clearly support the involvement of the genetic factors in the development of Graves’ disease. However, since this is well below 100%, environmental factors are also playing an important role in the development of disease. The magnitude of genetic contribution or familial clustering can be estimated by dividing the lifetime risk to a second sibling (in cases in which the first has the disease) by the population frequency of the disease to produce the lambda (λ) sib (s) statistic (9). A λs of 1 implies no genetic contribution to disease, whereas a disorder arising from rare single-gene defects with high penetrance, such as hemophilia, will have a λs of greater than 1000. We have estimated that Graves’ disease has an overall λs of 7.5–10, supporting a genetic contribution to disease (10). However, the magnitude of this value suggests that Graves’ disease develops as a result of a complex inheritance pattern to which several genetic susceptibility loci and environmental factors are likely to contribute. Analysis of familial clustering data by gender further highlights the female preponderance of Graves’ disease (6). The risk of Graves’ disease developing in a sister when her sibling already has the disease is reported to be between 5 and 10%. In contrast, the risk for a brother is 0.9–7.4%. This suggests that a sister is 5.4–12.6 times more likely and the brother 1.2– 7.4 times more likely to develop Graves’ disease than an individual in the general population when a sibling already has disease. The reasons for the female preponderance are unknown. A number of hypotheses have been advanced, including effects resulting from differences in sex hormones. Although it has also been suggested that gender differences may arise because of differences in the sex chromosomes, this needs some clarification. It seems most unlikely that gender differences could arise because of susceptibility loci on the X chromosome. If such a locus existed, a dominant effect would lead to no difference between males and females, whereas a recessive effect would lead to an increase in Graves’ disease in males (since they only have one X chromosome they only need one susceptibility allele). Gender differences could arise because of a susceptibility locus on the Y chromosome, but this would need to confer protection to males. In an attempt to identify loci conferring susceptibility to Graves’ disease, two main approaches have been adopted: the candidate gene approach and the genome-wide search

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using linkage analysis (10). Advances in the dissection of Graves’ disease susceptibility loci have been made by linkage analysis and allelic association methods. These have been greatly assisted by the emergence of detailed maps of the human genome and several collections of large population-based, case–control, family-based data sets. Because Graves’ disease is immunologically mediated, many researchers employing the candidate gene approach have focused on genes that regulate the immune response and also the target antigen: the TSH receptor. III. MAJOR HISTOCOMPATIBILITY COMPLEX REGION The human major histocompatibility complex (MHC) region on chromosome 6p21 encodes proteins involved in the human leukocyte antigen (HLA) system. This chromosomal region is well researched and may influence the ultimate outcome of somatic recombination by affecting the selection of T cells and B cells. The region can be organized into three main gene clusters. The class I region genes include those encoding the α-chains of HLA-A, HLA-B, and HLA-C antigens. These are membrane-bound proteins expressed on the cell surface of the nucleated cells involved in the process of presentation of endogenous peptide to the cytotoxic (CD8⫹ ) T lymphocytes. The class II gene region, on the other hand, encodes proteins expressed on specialized antigen-presenting cells, including the macrophages and B lymphocytes and also, under certain circumstances, other cell types. Class II molecules are likely to be involved in the autoimmune disease process as they bind products generated by the degradation of proteins in the endocytic pathway. These complexes can then stimulate T-helper (CD4⫹ ) lymphocytes. The class III region contains genes that encode immune regulator proteins, including some of the cytokines. Several population-based case–control studies have shown an association between Graves’ disease and polymorphisms within the MHC–HLA region. Consistent associations have been reported between class II gene polymorphisms and, specifically, HLADR3 (Table 1). The magnitude of the contribution of the HLA region to Graves’ disease is summarized in Table 1, which shows relative risks of between 1.9 and 3.8 for polymorphism in the class II region. Reports of the association between Graves’ disease and other Table 1 Reported Associations Between MHC-HLA Region and Graves’ Disease Since 1990 Size of data set (n)

HLA association

Relative risk

Mangklabruks et al., 1991 (26)

130

Badenhoop et al., 1992 (51) Badenhoop et al., 1995 (52) Yanagawa et al., 1996 (53)

374 542 169

Cuddihy and Bahn, 1996 (54) Barlow et al., 1996 (13)

134 177

Heward et al., 1998 (11)

592

DR3 DQB1*0201 DR3 DQA1*0501 DR3 DQA1*0501 DR3 DR3 DQA1*0501 DRB1*0304 DQB1*0301/4 DQA1*0501

3.4 3.3 2.3 2.5 2.5 3.7 3.5 2.7 3.8 2.7 1.9 3.2

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class II genes are less convincing. Strong linkage disequilibrium exists across the HLA region, for example, HLA-DRB1*0304, DQB1*02, and DQA1*0501 are in tight linkage disequilibrium. This makes it difficult to ascertain which allele is exerting a primary effect (11) or whether susceptibility is conferred by a haplotype. Part of the reason for this uncertainty results from the fact that there are 14 alleles at DRB1*0304, DQB1*02 and DQA1*0501, and most case-control data sets have lacked the power to withstand the appropriate correction factor to identify an independent effect. Yanagawa et al. (12) reported for the first time an independent effect of the HLA-DQA1*0501 allele, conferring a greater risk than the HLA-DR3. Barlow and co-workers (13) subsequently reported an uncorrected significant association of HLA-DQA1*0501 in DR3-negative subjects in the United Kingdom. Using our data set that comprises more than 1000 cases and controls, we are unable to confirm the independent effect of the HLA-DQA1*0501 allele in DR3 negative subjects (Nithiyananthan, unpublished data). The population-based case-control study, is one of the most sensitive methods for the identification of susceptibility loci exerting small effects. However, this approach lacks specificity and can lead to false-positive results as a consequence of population stratification and inadequate matching of cases and controls (10). Mismatching can be minimized by large data sets but unfortunately most published reports lack sufficient power to detect adequately a true effect and exclude a random chance event. For example, for a susceptibility locus that confers a relative risk of 2.0 for development of Graves’ disease, and a susceptibility genotype frequency of 20%, a total data set of more than 800 cases and controls would be needed to have an 80% power to achieve a result with significance of p ⬍ 0.001. Most published case–control studies have used numbers well below this figure. Population stratification can be eliminated using the intrafamilial association study approach using family-based data sets. One such approach utilizes the transmission disequilibrium test (TDT), which requires genotype data and therefore DNA from both parents and at least one affected sibling (14). This approach can be further strengthened by incorporating data from unaffected siblings to exclude segregation distortion. We have, for the first time, reported an allelic association between the HLA class II haplotypes DRB1*0304-DQB1*02-DQA1*0501 and Graves’ disease using the TDT approach (11). These data provide evidence for linkage in the presence of linkage disequilibrium between HLA and Graves’ disease. Classic linkage analysis can also be used to identify susceptibility loci. This method has been used successfully to identify the genes that have major effects. However, it has a limited ability in detecting genes that have modest effect (15), which again, in part, relates to data sets of inadequate size. In Graves’ disease it is likely that a number of susceptibility loci, each with a modest effect, are contributing to disease development. Power calculations suggest that large numbers of Graves’ disease families are required to pick up these effects (between 600 and 1000 sib-pairs). It is not surprising, therefore, that this approach to date has met with a very limited success and largely failed to detect the HLA region as a susceptibility locus. A recent report, however, does provide weak evidence for linkage between HLA and Graves’ disease (16). As this was reported in only 77 sib-pairs, this result and certainly the magnitude of the effect at this locus should be viewed with caution. Although the exact mechanism by which polymorphism in the HLA region confers susceptibility to Graves’ disease is unknown, it is highly likely that polymorphism within the HLA region results in differences in amino acid sequences. These differences could


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affect antigen-binding sites, thereby influencing antigen-binding affinity, the nature of the stimulation of T lymphocyte, and the development of the immune response. Although MHC-HLA association is a general feature of autoimmune diseases (17) there is evidence to suggest this region may be facilitating a tissue-specific effect. Using animal models it was possible to show that by swapping diabetogenic and autoimmune thyroid MHC haplotypes, the tissue in which the autoimmune process developed could be changed. Hence thyroiditis was initiated in an animal model of diabetes with thyroid MHC haplotype (18,19). IV.

CYTOTOXIC T-LYMPHOCYTE-ASSOCIATED-4 GENE

An immune response initiated by the presentation of an antigen by an MHC-HLA class II molecule to the T-cell receptor on the T lymphocyte can only progress in the presence of a second costimulatory pathway. This can either be provided by local infection (20) or by an interaction between the cluster designation-28 (CD28)/cytotoxic T-lymphocyte associated-4 (CTLA-4) molecules on the T lymphocyte and the B7 molecule of the antigen presenting cell. The interaction between CD28/CTLA-4 and B7 molecule appears to be an important step in the process of autoimmune disease (Fig. 1). Without costimulation provided by CD28/B7 binding the T lymphocyte remains in a state of anergy and may even undergo cell death. CD28 and CTLA-4 are two T lymphocyte surface molecules that bind their ligands B7.1 and B7.2 (CD86 and CD80, respectively) on antigen-presenting cells and other activated cells (21,22). CD28 is expressed on resting and activated T lymphocytes, and its interaction with the B7.1 molecule on the antigen-presenting cell leads to expansion of the antigen-specific T-lymphocyte and cytokine production (23,24). The CTLA-4 molecule, on the other hand, is only produced after activation of T lymphocyte. Its interaction with the B7.2 on the antigen-presenting cell modulates the immune response, especially CD4 responses, by downregulation of T-cell receptor (25,26). This pathway is tightly regulated, and can strongly influence the immune response. CD28 and CTLA-4 genes are closely located on chromosome 2q33, suggesting a common ancestral origin. Yanagawa and co-workers in 1995 reported an association between a polymorphism of the (AT)n microsatellite marker in the 3′untranslated region of the CTLA-4 gene and Graves’ disease (27). A single nucleotide polymorphism (SNP) in exon 1 of this gene (A → G polymorphism) was subsequently found to be in linkage disquilibrium with the (AT)n microsatellite, with the G allele being associated with disease in a European case–control data set. Linkage to type 1 diabetes has also been reported (28). Further reports have shown association of the A-G polymorphism of the CTLA-4 gene with Graves’ disease (29–31), Hashimoto’s thyroiditis (31,32), type 1 diabetes (33), Addison’s disease (32,34), celiac disease (35,36), and primary biliary cirrhosis (37). We have also shown intrafamilial allelic association between the G allele of the A-G polymorphism and Graves’ disease in a cohort of 179 families (30), and therefore excluded population stratification as an alternative explanation. We also demonstrated that the G allele was associated not only with the disease but also with its severity at the time of presentation by showing that the presence of the GG genotype is associated with a more severe biochemical disturbance of circulating free thyroxin levels (30). Family linkage data are also available showing linkage of the CTLA-4 gene region to Graves’ disease in a UK data set (16) and linkage to thyroid antibody production in a

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Figure 1 The thyroid-stimulating hormone receptor (TSHR) antigen is presented to the T-cell receptor (TCR) by the major histocompatibility complex (MHC) class II molecules on the antigen-presenting cell (APC), leading to the development of potentially autoreactive T cells. For the progression of an immune response, a second signal is required, which is provided by the interaction of B7 (on the APC) and CD28 (on the T lymphocyte). The interaction of B7 and cytotoxic T-lymphocyte-associated-4 (CTLA4) leads to a decrease of the T lymphocyte, largely by a decrease of the TCR. Disequilibrium of CD28 and CTLA-4 could lead to a more aggressive immune response and contribute to the autoimmune disease process. US data set (38). Linkage data from affected sib-pairs in the UK, as with HLA, was in a relatively small number of families, the magnitude of the contribution reported at this locus needs verification. Association and linkage between the CTLA-4 gene polymorphism and Graves’ disease merely suggests that there is likely to be a susceptibility locus in this chromosomal region. These data, however, do not pinpoint the locus to the CTLA-4 gene directly. Although polymorphism within the CTLA-4 gene may well confer susceptibility to Graves’ disease, it is just as likely that the polymorphisms studied are in linkage disequilibrium with a disease-causing mutation, even in a neighboring gene. Genes in this region include CD28, the inducible costimulatory molecule (ICOS) gene, Caspace 8, and Caspace 10, all of which are equally good immune response candidate genes. Only comprehensive fine mapping of all polymorphisms in the region leading to the determination of maximal point and extent of linkage disequilibrium will identify the location of the etiological mutation. Examination of one SNP in a neighboring gene such as CD28 merely excludes that polymorphism but not the gene (38). Comprehensive screening for all polymorphisms is vital.


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Polymorphism of the CTLA-4 gene leading to alteration in gene function may lead to the development of the autoimmune disease process by interfering with the regulatory role of CTLA-4 in the CD28/CTLA-4 -B7 pathway. Functional studies are now emerging in a number of disease states including Graves’ disease (39), myasthenia gravis (40), and multiple sclerosis (41). Although none of these studies has demonstrated differences between subjects with and without disease, there are reports of differences in T-cell proliferation and CTLA-4 expression between individual CTLA-4 genotypes. Again, although these data are interesting and provide a potential functional link to the autoimmune disease process, they do not directly incriminate the A-G polymorphism as an etiological polymorphism. Finally a number of candidate gene loci have been examined with respect to the development of Graves’-associated orbital disease including the CTLA-4 gene region. Although association between the CTLA-4 gene and eye disease has been reported, this was in a data set of 94 subjects with eye disease and 94 subjects without eye disease (42). These data lacked sufficient power to support the hypothesis that eye disease is related to CTLA-4 genotype. In our own data set of 323 patients with Graves’ disease without eye disease and 161 patients with eye disease (NOSPECS classification 2–6), there were no differences in CTLA-4 genotype between the groups. As might be expected, however, multiple regression analysis confirmed association between thyroid eye disease and smoking (42a). V. GENOME-WIDE SEARCHES There is little doubt that the MHC-HLA region and CTLA-4 gene region contribute to the genetic susceptibility to development of Graves’ disease. However, these regions do not explain all of the genetic contribution to disease. Although candidate gene studies will continue to play an important role in the identification of susceptibility loci, genome-wide searches have also been employed to identify further loci. A number of new candidate loci have been identified by genome-wide linkage analysis. As with many other complex diseases, replication of linkage in independent data sets has proved problematic and this approach has so far failed to deliver novel candidate genes. The GD-1 gene region is located on chromosome 14q31 (43,44). Chromosome 14 was initially screened with 14 microsatellite markers in 323 individuals from 53 families. The inclusion of additional markers within the region of linkage were used in a multipoint parametric analysis that gave a significant maximum logarithm of odds (LOD) score of 2.5 between the markers D14S81 and D14S1054 (⬃3cM apart), with the data supporting a model of recessive inheritance. Further analysis has localized GD-1 to within 2cM of the multinodular goiter-1 (MNG-1) locus identified in a family pedigree of subjects with a multinodular nonautoimmune thyroid goiter (45). This raises the possibility that MNG1 and GD-1 are the same and that this locus confers susceptibility to both Graves’ disease and multinodular goiter. Within the chromosomal region of GD-1 are other possible thyroid autoimmune candidate genes such as the TSHR gene, immunoglobulin heavy chain gene (IgH), the T-cell receptor α gene, the insulin-dependent diabetes mellitus 11 (IDDM11) gene, and the estrogen receptor β (ESRβ) gene. However, most if not all of these candidates are outside the region of linkage identified as GD-1. Association studies have revealed conflicting results from some of the candidate genes in this region, including the

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Table 2 Candidate Genes That Have Been Studied in Graves’ Disease

Candidate gene

Study (Ref.)

TSHR

Cuddihy et al. (55) Watson et al. (56) Kotsa et al. (57) Allahabadia et al. (58)

IL-IRA

Blakemore et al. (59) Heward et al. (60) Allahabadia et al. (61) Heward et al. (62) Badenhoop et al. (51) Caven et al. (63) Hunt et al. (64) Heward et al. (65)

IDDM2 LMP2 and LMP7 TNF-β IL-4

Size of data set (n)

Association (⫹) or no association (⫺)

246 297 425 562 (Caucasians) 167 (Chinese) 361 680 537 670 347 149 239 672

⫹(females) ⫺ ⫺ ⫺ ⫺ ⫹ ⫺ ⫺ ⫹(2° to DR3) ⫹ ⫺ ⫹ ⫺

TSHR, thyroid-stimulating hormone receptor; IL-1RA, interleukin 1 receptor antagonist; LMP, large multifunctional proteasome; TNF-β, tumor necrosis factor-beta; Il-4, interleukin-4.

TSHR gene (see Table 2). It is unlikely that current markers at GD-1 or MNG-1 represent the known polymorphisms in the candidate genes listed above and both replication and fine mapping of the GD-1/MNG-1 locus are needed to identify the Graves’ disease-specific locus. Using the same data set used to identify the GD-1, Tomer and co-workers found a second Graves’ disease locus designated GD-2 that was mapped onto 20q11.2 (46). Multipoint parametric linkage analysis of this region showed a significant maximum LOD score of 3.5 in a 6cM region between microsatellite markers D20S195 and D20S107, assuming a recessive mode of inheritance. Similar results were shown when the data were analyzed using a nonparametric method, which has the advantage of not assuming the mode of inheritance. Several candidate genes have been mapped in this region, including the interleukin-6 nuclear factor (NF-IL6). NF-IL6 gene is a good candidate gene for autoimmunity as it encodes protein that binds to several regulatory regions of other cytokines. In 45 families collected as part of the original 53 families described above, linkage has also been reported in a region designated GD-3 on chromosome Xq21.33–22 (47). The X chromosome was initially screened with 20 microsatellite markers, and multipoint linkage analysis of 8 markers between DXS1196 to DXS1001 (⬃46cM) produced a maximum LOD score of 2.5, suggestive of linkage. The same report also excluded a number of gender-related candidate genes as susceptibility loci for Graves’ disease. In the UK sib-pairs in which linkage was reported at HLA and CTLA-4 gene region, linkage has also been reported on chromosome 18q21 (48) and the X chromosome at Xp11, conditioned for allele sharing at the CTLA-4 gene region (49). Linkage at marker DS18S487 (48) has previously been reported in type 1 diabetes and rheumatoid arthritis, suggesting the possibility of a general autoimmunity gene at this locus. No evidence for linkage in this data set was found at GD-1 or GD-3. It should be pointed out, however, that the small size of this data set does not have the power to exclude an effect equivalent to GD-1 or GD-3. Furthermore, despite the small size of this data set, subgroup analysis


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was performed to replicate GD2 (50). Such data should, therefore, be viewed with extreme caution. At the present time replication of linkage data in family data sets of sufficient size to detect loci of modest effect is needed to confirm the present findings and to quantify the contribution of linked loci to the genetic susceptibility to Graves’ disease. Preliminary data from the UK suggest that the HLA and CTLA-4 gene regions may contribute up to 50% of the familial clustering, leaving the remaining 50% to be explained by as yet unknown loci (16). VI.

OTHER CANDIDATE GENES

Table 2 shows the results of the candidate genes examined to date. Most of these have been tested in population-based case–control studies. The inconsistent findings are almost certainly the result of inadequately sized data sets and, in some instances, poor matching of controls. At present only the HLA gene cluster and the CTLA-4 gene have been consistently reported to be associated with Graves’ disease, in both case–control and family–based data sets. VII.

CONCLUSION

Graves’ disease is a common complex autoimmune disease of unknown etiology. There is clear evidence for an immunological basis, with TSHR acting as the primary autoantigen. Clustering in families and twin data confirm an important role for genetic causes, with the same studies highlighting an equally important contribution from the environment. The HLA and CTLA-4 gene regions undoubtedly contain important susceptibility loci, although the magnitude of their effect awaits confirmation. Although genome-wide searches have identified chromosomal regions of linkage to Graves’ disease, including GD-1, GD-2, GD-3 chromosome 18, and the X chromosome, these preliminary findings need replication and novel candidate genes within these regions are eagerly awaited. Data from HLA and the CTLA-4 gene regions suggest that susceptibility loci are common polymorphisms also present in the general ‘‘unaffected’’ population. For example, in the United Kingdom (11) the HLA susceptibility haplotype DRB1*0304DQB1*02-DQA1*0501 is present in 47% of the patients with Graves’ disease and 32% of the controls. Similar findings have been observed for polymorphisms of the CTLA-4 gene present in 42% of the cases and 32% of the controls (30). These data support the hypothesis that common polymorphisms that protect or predispose to development of autoimmune diseases are the same common polymorphisms that confer resistance or susceptibility to development of infectious disease. Over the last 10 years or so we have gained a greater understanding of factors leading to the development of Graves’ disease. We are beginning to unravel some of the susceptibility loci that make up the genetic contribution to the development of disease. The establishment of large case–control and family-based data sets for linkage and association analysis combined with the publication of human genome sequence data are likely to lead to further advances in our understanding of the genetic susceptibility to the development of Graves’ disease. ACKNOWLEDGMENTS This work is supported by the grant (No. 95/3717) from the Wellcome Trust and the Regional Research and Development NHS Executive, West Midlands, United Kingdom.

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14 Environmental Factors in the Pathogenesis of Graves’ Disease ¨S THOMAS H. BRIX and LASZLO HEGEDU Odense University Hospital, Odense, Denmark

I.

INTRODUCTION

Graves’ disease (GD) is an organ-specific autoimmune thyroid disorder characterized clinically by hyperthyroidism, various degrees of diffuse goiter, ophthalmopathy, and, less commonly, pretibial myxedema (1). The hyperthyroidism is due to the presence of autoantibodies that bind to and activate the thyrotropin receptor, thus simulating the action of thyrotropin (2). Although GD is one of the most common thyroid disorders its cause is still incompletely understood. According to current thinking (3–5), GD is considered as a member of the group of diseases referred to as ‘‘complex diseases,’’ which include insulin-dependent diabetes mellitus, rheumatoid arthritis, osteoporosis, and hypertension, among others. These conditions are common, show familial clustering but no Mendelian mode of transmission, and vary in their prevalence and severity. They are thus multifactorial, with the clinical phenotype representing the net effect of all the contributing environmental, endogenous, and genetic factors (Fig. 1). In these complex conditions, GD being no exception, it has been difficult to separate environmental influences from genetic susceptibility (6,7). This chapter will briefly review current knowledge in this field with focus on the influence of environmental factors in the causes of GD. The importance of genetic factors in the etiology of GD are considered elsewhere in this volume. The topics covered are wide-ranging and each could be the subject of detailed review in its own right. This chapter, however, is presented as an overview of the main issues and is primarily aimed at clinicians rather than theoreticians. 127

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Brix and Hegedu¨s

Figure 1 The development of clinically overt Graves’ disease seems to involve a complex interplay of genetic, endogenous, and environmental factors. At present, it is, however, not clear how and to what degree, if any, the candidate genes or genetic markers interact with the endogenous or environmental risk factors. HLA, human leukocyte antigen; CTLA-4, the cytotoxic T-lymphocyte antigen 4; AITD-1, GD-1, GD-2, and GD-3, susceptibility loci for GD, located on chromosome 6, 14, 20, and X, respectively; TSHR, the thyrotropin receptor. (Modified from Ref. 7.)

II. DO ENVIRONMENTAL FACTORS PLAY A ROLE IN THE CAUSES OF GRAVES’ DISEASE? The influence of genetic and environmental factors in the causes of ‘‘complex diseases’’ have traditionally been studied in families and twins (6). Family and twin studies have provided indisputable evidence for the contribution of both genetic and environmental factors in the development of GD (7–9). This is based on familial clustering of GD and on concordance rates for GD being significantly higher in monozygotic than in dizygotic twins. Since monozygotic twins share all genes and dizygotic twins, on average, share half of their genes, the difference in concordance rates can be explained by genetic factors. On the other hand, even with more than 25 years of follow-up, the crude probandwise concordance rates for GD are no higher than 30–60% in monozygotic twins (8,9). In other words, although they are genetically alike, in 40–70% of monozygotic twins one twin develops GD but the second twin does not, thus providing evidence that environmental factors play a causative role in GD. This is further supported by recent studies that have assessed the role of specific candidate genes or genetic markers in the causes of GD. These studies demonstrate that a large number of healthy subjects harbor one or several of the currently known genetic risk markers for GD without having the disease (3,7,10). The considerable regional variations in the prevalence of GD demonstrated in large epidemiological surveys (11–13) also point strongly toward environmental factors. Accepting, therefore, that environmental factors play a role in the causes of GD, how large is the effect? In a recent population-based twin study comprising data from over 8,900 Danish twin pairs, it has been estimated that 79% (95% confidence interval, 64–90%) of the liability to develop clinically overt GD is attributable to additive genetic factors (heritability), whereas environmental factors explain the remaining 21% (95% confidence interval,

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10–36%) (9). This does not mean that 79% of all cases of GD are due to genes alone or that 21% are due to environment alone. It is important to point out that no component causes disease alone; rather, they interact to produce disease. To summarize, family and twin studies have provided irrefutable evidence of a substantial influence of environmental factors in the causes of GD. III. IDENTIFICATION AND CAUSALITY OF SPECIFIC ENVIRONMENTAL FACTORS Accepting that environmental factors are involved in the development of clinically overt GD, can they be identified? The triggering role of environment in disease development has been suggested since the first descriptions of GD in the 19th century. Since then a number of specific environmental factors have been associated with the development of GD, the most important being the level of dietary iodine intake, cigarette smoking, and stressfull life events (Fig. 1). Before describing these environmental factors in detail, it is worth asking: How do we separate causal from noncausal associations? In clinical medicine, we normally use randomized controlled trials to provide evidence of causal relationships for treatments and preventions. However, for obvious reasons, randomized controlled trials are rarely feasible when studying causes of disease. Thus, with respect to disease causation it is not possible to prove causal relationships with certainty. It is only possible to increase one’s conviction of a causal relationship, by means of empiric ‘‘evidence’’ to the point where cause is established for all intents and purposes. This usually means that several studies must be done to build up ‘‘evidence’’ for or against cause (14). In practice, it has been widely accepted that the following aspects of an association should be considered when attempting to differentiate causal from noncausal explanations (14,15): strength, consistency, specificity, temporality, dose–response, and biological plausibility (Table 1). A summary of the existing evidence for or against a causal relationship between specific environmental exposures and Graves’ disease with respect to these features is given in Table 2. A. Iodine As well as being an essential substrate for the biosynthesis of thyroid hormone, iodine also has a number of effects on thyroid growth and function (16,17). The most common Table 1 Findings Suggesting a Causal Association Finding Strength Consistency Specificity Temporality Dose–response Biological plausibility

Comments Strong associations are more likely to be causal than weak ones. The repeated observation of an association in different populations under different circumstances. A cause leads to a single effect, not multiple. The cause precedes the effect in time. Larger exposures to cause are associated with higher rates of or more severe disease. The association makes sense, according to the biological knowledge of the time.

Source: Compiled from Ref. 15.

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Table 2 Summary of the Evidence for or Against a Causal Relationship Between Specific Environmental Exposures and Graves’ Disease Features of the association

Environmental exposures Iodine

Smoking

Stress

Infections

Strength Consistency Specificity Temporality Dose–response Biological plausibility

Yes Yes No Yes Yes Yes

Yes Yes No Yes Yes Yes

Yes Yes No Unknown Probably Yes

No No No Unknown Unknown Yes

Causality likely at the present time?

Yes

Yes

Probably

No

abnormalities leading to thyroid disease are autonomous growth of follicular tissue and thyroid autoimmunity. Since both processes are influenced by the iodine intake level, it is not surprising that iodine has been implicated as playing an important role in the causes of most thyroid diseases. Considerable evidence exists both in human populations (18) and in animal models (19) that iodine plays an important and probably causal role in the development of GD in genetically predisposed individuals. Epidemiological surveys have repeatedly demonstrated that differences in prevalence and/or incidence of overt GD in different parts of the world closely mimic the magnitude of the iodine intake, with GD being more prevalent in areas with the highest iodine intake (11–13,20). Furthermore, recent longitudinal data from Austria (21) demonstrate that an increase in iodine intake from low to a normal level is accompanied by a twofold increase in the incidence of hyperthyroidism secondary to GD. Although rare, iodine-induced hyperthyroidism has also been described in iodinesufficient areas (22). However, in the great majority of these patients, if not all, the induced hyperthyroidism is secondary to an underlying thyroid autonomy (22,23). On the other hand, the level of thyrotropin receptor antibodies has been shown to increase significantly in hyperthyroid patients with GD when given excess iodine (24). At present there are, however, no epidemiological data available regarding the consequences of incidental exposure to iodine excess (e.g., by amiodarone or kelp tablets, iodine-containing x-ray contrast agents, or iodine-rich foodstuffs) in subjects predisposed for GD living in iodinesufficient areas. The above epidemiological observations suggest that iodine can affect the course of GD. It has long been recognized that antithyroid drug therapy reduces thyroidal iodine content and that patients given iodine supplementation after discontinuing drug therapy are more likely to have relapses than patients not given iodine (25). More recently it has been shown that the response to antithyroid drugs in patients with GD is more rapid and the dose required to control the disease is smaller in iodine-deficient areas than in iodinereplete areas (26,27). In line with these observations, the remission rate of GD after antithyroid drug therapy is generally lower in areas with a high iodine intake than in areas with a low to normal iodine intake (18,28). Moreover, the difference in GD remission rates between the United States and Europe has, at least in part, been attributed to the higher iodine intake in the United States (28,29). GD is more likely to recur following thyroidectomy in areas with a high iodine intake than in areas with a normal iodine intake


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(30). Thus, it seems evident that iodine administered to subjects genetically predisposed to GD may result in development of a clinically overt disease. The exact mechanisms by which iodine provokes the development of overt GD in susceptible individuals are uncertain (19). Based on the observation that iodine, in vitro, can stimulate B lymphocytes to increased production of immunoglobulin (18), it has been speculated that iodine may induce GD by enhancing the activity of lymphocytes primed by thyroid-specific antigens (31). Consonant with this view is the observation that excess iodine administered to patients with GD significantly increased the thyrotropin receptor antibody titers (24). In summary, although the mechanisms by which iodine induces GD in predisposed individuals remain to be defined, the relation between iodine intake and overt GD is well established in terms of both epidemiology and disease course. The available data show consistency, temporality, a dose–response pattern, and the observations are all biologically plausible. In combination, these features strongly indicate a causal relationship between iodine intake and the development of overt GD in genetically susceptible subjects (Table 2). B.

Smoking

Although the global influence of cigarette smoking on the immune system is not yet fully understood, it has long been recognized that smoking has a number of immunological effects involving both the humoral and cellular components of the immune response (32). Some of these immunological effects could theoretically have implications for the genesis of autoimmunity. This is supported by several case–control studies reporting an increased prevalence of autoimmune diseases among smokers compared to nonsmokers (32). Smoking has thus emerged as an environmental factor contributing to the development of autoimmunity. A relationship between cigarette smoking and GD with or without ophthalmopathy was first suggested in 1987 in a small series of patients by Ha¨gg and Asplund (33). Despite major differences in study designs, size of study populations, definitions of smokers and nonsmokers, iodine intake, and methods used for evaluating the degree of ophthalmopathy and thyroid function, in a large number of retrospective (34–40) and in a few prospective (41,42) studies smoking has subsequently repeatedly been associated with an increased risk of GD and especially Graves’ ophthalmopathy. It has, however, been speculated that the association between smoking and GD is an artifact and occurs indirectly through other (confounding) factors such as stress or other neurobehavioral changes related to hyperthyroidism (43,44). However, in a recent study from Japan (38), even after adjusting for stressful life events, smoking was still an independent risk factor for GD. It is also worth noting that smoking has not been found to be associated with hyperthyroidism secondary to toxic nodular goiter (Plummer’s disease) (34,37). Although the information is not given directly, it seems that in most studies, persons with Graves’ disease, with or without ophthalmopathy, began smoking more than 1 year prior to diagnosis. This was certainly the case in our own data set (39). These observations suggest a temporal, cause and effect relationship between smoking and GD. In GD with ophthalmopathy, recent prospective data clearly establish such a temporal relationship (42). Evidence supporting a dose–response effect between smoking and GD with ophthalmopathy (42) and without ophthalmopathy (39) has been reported. In their prospective

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Figure 2 Individual intrapair pack-year difference (pack years of the proband minus pack years of the healthy co-twin) in twin pairs discordant for clinically overt Graves’ disease but concordant for smoking. Note that each bar represents a twin pair and that a positive value is obtained when pack years of the proband are higher than pack years for the corresponding co-twin; proband versus co-twin, 13 pairs, p ⫽ 0.048. (Modified from Ref. 39.)

study, Pfeilschifter and Ziegler (42) found that the relative risk for eye disease increased in proportion to the current number of cigarettes smoked daily. In a recent twin study (39), it was shown that among twin pairs concordant for smoking (both twins smoke) but discordant for GD (only one of the twins has GD), the twin with GD smoked significantly more than the healthy co-twin (Fig. 2). This finding suggests a positive correlation between the cumulative cigarette consumption (counted in pack-years) and the development of GD in genetically susceptible individuals. In sharp contrast to previous retrospective data (36,40), more recent prospective data (42) indicate that former smokers have a lower risk of developing eye disease than current smokers even with a comparable lifetime tobacco consumption. This suggests that giving up smoking may be beneficial. Unfortunately, there are no prospective data on whether cessation of smoking reduces the degree of hyperthyroidism, or a preexisting ophthalmopathy, or the risk of development or deterioration of ophthalmopathy. As with iodine, smoking may also affect treatment outcome in GD. In a historical cohort study comprising 150 consecutive patients treated with high-dose oral prednisone and radiotherapy for severe ophthalmopathy, a response to treatment was seen in up to 93.8% of the nonsmokers but in only 68.2% of the smokers (45). Furthermore, in randomized treatment studies ophthalmopathy was three to five times more likely to improve in nonsmokers than in smokers, whereas ophthalmopathy was more likely to get worse in smokers than in nonsmokers (45,46). How smoking contributes to the development of GD with or without ophthalmopathy is at present unclear, although several mechanisms have been suggested (40,43,47). Regardless of the exact mechanisms, the association between smoking and GD, and especially GD with ophthalmopathy, is strong and well established (Table 2). C.

Stress

The triggering role of stressful life events in disease development has been suggested frequently since the very first descriptions of GD in the early 19th century (48,49). Thanks to the development of standardized methods for identification, measurement, and scoring of negative/adverse (stressful) as well as positive life events, this hypothesis is now sup-


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ported by substantial data. The first study to use a standardized methodology in the evaluation of the impact of stressful life events on the development of GD was published in 1991 by Winsa and colleagues (50). The impact of stressful life events was evaluated by comparing the answers to a standardized questionnaire about life changes from 208 subjects with newly diagnosed GD to those from 372 matched control subjects. Compared with controls, subjects with GD reported more negative life events in the 12 months preceding the diagnosis, and negative life event scores were also significantly higher (odds ratio 6.3, 95% confidence interval 2.7–14.7 for the group with the highest negative score). In spite of methodological differences, similar results have been reported from England (51), Italy (52), Hong Kong (53), and Yugoslavia (54). These studies have, however, been criticized for inappropriate control of a number of pertinent modulating factors such as social support, mood disturbances, coping skills, and smoking, which all may influence the immune system (32,55). In one recent study (38), stressful life events were still strongly associated with GD (odds ratio 7.7, 95% confidence interval, 2.2–27) even after adjustment for daily hassles, social support, coping skills, smoking and drinking habits. Only two studies (38,50) have evaluated whether the association between stressful life events and GD show a dose–response pattern. In both studies, the relative risk of GD increased as the life event score increased, suggesting a dose–response relationship. Although a dose–response effect strongly supports a causal relationship, especially when coupled with a large relative risk, its presence does not exclude bias. Bias may, however, very well be present, since all published studies have been retrospective. Such a study design is highly vulnerable to bias, especially recall bias (48). Subjects with GD may be more prone to remember negative life events than controls, especially when such life changes are thought to be the cause of their disease. Thus, if present, recall bias is a serious problem because it will overestimate the strength of the association (48). In our opinion, recall bias is, to some degree, present in all of these studies. Another serious concern is the combination of the insidious onset of GD and information on stressful life events gathered in a retrospective manner, where by definition both the purported cause (stressful life events) and the effect (GD) are measured at the same time. This combination makes it almost impossible to determine which came first. Since it is absolutely necessary for a cause (stressful life events) to precede an effect (GD), the lack of such a sequence is a strong argument against a causal relationship. This is not to say that the right temporal relationship between stressful life events and GD is lacking, but rather that no film conclusions can be made due to the lack of prospective data. The mechanisms by which stress might precipitate GD in predisposed individuals remains to be clarified. According to current thinking, the role of stress is explained by tight relations between the hypothalamic–pituitary–adrenocortical axis, the central nervous system, and the immune system (48,49). The suggested pathways are that stress stimulates the hypothalamic–pituitary–adrenocortical axis with a consequent increase in serum glucocorticoids and activation of the autonomic nervous system, followed by release of catecholamines. This altered neuroendocrine equilibrium has a profound effect on the immune system through direct interaction of hormones and neuropeptides with specific receptors, leading to a change in the profile of cytokine secretion. In summary, the observed association between stress and GD is consistent, strong, probably dose-dependent, and biologically plausible. However, due to the lack of prospective data, no firm conclusions can be made with respect to the temporal sequence of stress (cause) and GD (effect).

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Infections

The idea that an infection might trigger the development of overt GD in genetically predisposed individuals has long been a popular theory (31,56,57). Infectious agents may induce thyroid autoimmunity by various well-described mechanisms (56), such as inducing alterations or modifications of self antigens, mimicking self antigens, activating superantigeninduced T cells or inducing expression of human leukocyte antigen (HLA) molecules on thyroid cells. One of the best-studied infectious agents in relation to GD is Yersinia enterocolitica (56,57). A possible relationship between Yersinia enterocolitica and GD was first suggested in the mid 1970’s by Bech and colleagues (58). In this study, antibodies against Yersinia enterocolitica (serotype 3) were found in 110 of 185 patients (59.5%) with newly diagnosed GD, compared to 27.7% in the control population. Results from subsequent retrospective case–control studies from different parts of the world have, however, been contradictory (57). Moreover, in studies showing an association, the antibody titers against Yersinia enterocolitica are generally low and there are no obvious correlations with age, gender, thyroid antibodies, or disease severity (57,58). In line with these observations is the finding that most patients with Yersinia infection do not develop GD including those who produce antithyrotropin receptor antibodies (56). In summary, although the proposed association between Yersinia enterocolitica infection and GD is biologically plausible, it does not show consistency, specificity, or temporality, and there is at present no evidence for a causal relationship. Numerous other infectious agents, such as influenza B virus, various retroviruses, human foamy virus, coxsackie B virus, and Mycoplasma species have also been investigated, but no convincing evidence has been produced. Thus, at present the role of infection in precipitating GD in humans remains purely hypothetical (1,56,57). E.

Other Environmental Factors

Additional proposed environmental risk factors for GD include certain drugs, in particular lithium (59) and amiodarone (23), as well as an adverse intrauterine environment reflected by low birth weight (60,61). For the time being, the evidence of a causal relationship between these environmental factors and GD is rather weak. Lithium-associated hyperthyroidism has only been reported in sporadic case reports or in small retrospective crosssectional studies with inappropriate control populations (59). Amiodarone-induced hyperthyroidism is a well-known condition (17,22), but prospective data show that long-term treatment with amiodarone (in an iodine-sufficient area) does not increase the prevalence of thyroid autoantibodies. This suggests that thyroid autoimmunity plays little, if any, role in the development of hyperthyroidism in amiodarone-treated subjects without underlying thyroid disorders (23). In a cross-sectional study of 305 women aged 60–71 years, the proportion of women with thyroglobulin and thyroid peroxidase antibodies decreased with increasing birth weight (60). In contrast, a recent population-based twin control study did not find any effect of birth weight, or several other birth characteristics, on the risk of developing clinically overt autoimmune thyroid disease (62). IV.

CONCLUSIONS

From this brief review of the role of environmental factors in the genesis of GD one can draw several conclusions. First, the influences of environmental exposures have seldom


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been studied in a prospective manner. Nevertheless, at present there are convincing epidemiological and clinical observations strongly indicating that the association between GD and iodine intake and smoking is causal. Second, with very few exceptions (38,50) the impact of various environmental factors on disease development has only been studied in isolation. That is, no study has taken the presence of a possible interaction between two or more environmental risk factors into consideration. It is clear that variation in iodine intake modulates the effect of smoking on the thyroid, with the predominant effect of smoking being goitrogenic and/or antithyroid when the iodine intake is low, and immunogenic when it is adequate (47). The relationship between smoking habits and stress is another example, demonstrating that environmental risk factors for GD can interact and thereby influence disease risk. Future studies aimed at clarifying the role of environmental factors in GD should, therefore, analyze as many factors as possible simultaneously with a multivariate statistical method in order to determine both their independent and combined influences on disease development. Third, besides two recent twin case–control studies (39,62) the impact of environmental factors on the development of GD has never been studied in conjunction with the genetic background. Neither is it clear whether the environmental risk factors interact with the presently known susceptibility genes or genetic markers for GD, such as HLA-DR3 and CTLA-4 (3,10). In the near future a large number of new susceptibility genes and their numerous allelic variants probably will be identified. Thus, it will be important to assess how modifiable environmental risk factors, such as iodine intake or smoking or both in combination, interact with these susceptibility genes to influence disease risk. At present, the known environmental risk factors in GD, as in most chronic diseases, have a very poor predictive value for disease occurrence. Therefore, stratifying according to genetic susceptibility at one or more loci will greatly improve the predictive value for disease occurrence among biologically susceptible individuals and may thus help us to target preventive and therapeutic interventions. ACKNOWLEDGMENTS The present work has been supported by grants from the Agnes & Knut Mørks Foundation and the Clinical Research Institute, University of Southern Denmark. REFERENCES 1. Weetman AP, McGregor AM. Autoimmune thyroid disease: further developments in our understanding. Endocr Rev 1994; 15:788–830. 2. Smith B, McLachlan SM, Furmaniak J. Autoantibodies to the thyrotropin receptor. Endocr Rev 1988; 9:106–121. 3. Brix TH, Kyvik KO, Hegedu¨s L. What is the evidence of genetic factors in the etiology of Graves’ disease?—a brief review. Thyroid 1998; 8:627–634. 4. Philippou G, McGregor AM. The aetiology of Graves’ disease: what is the genetic contribution? Clin Endocrinol 1998; 48:393–395. 5. Davies TF. Autoimmune thyroid disease genes come in many styles and colors. J Clin Endocrinol Metab 1998; 83:3391–3393. 6. Martin N, Boomsma D, Machin G. A twin-pronged attack on complex traits. Nat Genet 1997; 17:387–392. 7. Brix TH, Hegedu¨s L. Genetic predisposition versus environmental factors in autoimmune thy-

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15 Graves’ Disease and Myasthenia Gravis MICHAEL WEISSEL University of Vienna, Vienna, Austria

It may be difficult to differentiate the ophthalmoplegia of ocular myasthenia gravis and that of Graves’ ophthalmopathy clinically. The ocular symptom most likely to occur in both disorders is diplopia. Uni- or bilateral ptosis, which is the other leading symptom of myasthenia gravis, can also, albeit rarely, occur in Graves’ disease. Indeed, even most recent tables of differential diagnosis of myasthenia gravis put endocrine orbitopathy in first place (1). The ocular symptoms of both diseases can be exacerbated by iodinated contrast media (2). The association of Graves’ disease and myasthenia gravis had been described in individual cases in the early 20th century (3). The association is believed to be due to a shared genetic predisposition to organ autoimmunity and not to a direct effect of one disorder on the other (4). Indeed, in white persons both diseases have been shown to have a significantly higher frequency of HLA B8 and DR 3 than the control population (5,6). In myasthenia gravis this association is especially strong for female patients with earlyonset disease and for patients with thymic hyperplasia (7). Data regarding the actual prevalence of myasthenia gravis in Graves’ disease in comparison with the general population are sparse. Table 1 shows that available data describe a 5- to 30-fold increase of the occurrence of myasthenia gravis in Graves’ disease with a prevalence of 25 to 350 :100,000 in comparison to the prevalence observed in the general population of 5 to 12 : 100,000 (11–14). Acetylcholine receptor-binding antibody seropositivity occurs in a small proportion of patients (4: 50 patients; (15)) with Graves’ ophthalmopathy but, by itself, does not seem to identify an individual at risk of myasthenia gravis. This and the relatively small increase in prevalence contradicts the use of circulat-

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Weissel

Table 1 Prevalence of Myasthenia Gravis (MG) in Graves’ Disease (GD) Reference

Prevalence (%)

Patients with GD

Patients with GD and MG

8 0.35 4000 14 9 0.14 22956 33 10 0.025 12000 3 Prevalence of MG in the general population: 5 to 12/100,000; prevalence of MG in GD: 25 to 350/100,000

ing acetylcholine receptor antibody determination as screening for concurrent myasthenia gravis in patients with Graves’ disease. On the other hand the prevalence of Graves’ disease in myasthenia gravis is difficult to judge. There are no data in the literature on the occurrence of euthyroid Graves’ disease (defined as classic eye signs and positive thyroid-stimulating hormone [TSH]-receptor antibodies with normal thyroid function) in the general population. Only data on thyrotoxicosis (of any origin) exist, as shown in Table 2. The prevalence of thyrotoxicosis in myasthenia gravis differs according to the reports (see Table 2) from 1.4 to 5.8%, and the prevalence of Graves’ disease from 0 (20) to 7.6% (16). An influence of different gender distributions of the two diseases is highly unlikely since the gender distribution of the myasthenia gravis patients studied shows a female preponderance of about 3:2 in all reports but one (18), which is similar to that described for thyrotoxicosis. As shown in Table 2, the prevalence of thyrotoxicosis is obviously higher in myasthenia gravis than in the general population, where it varies from 0.25 to 0.54% in women and from 0 to 0.21% in men (21–23). This relative increase, however, is rather small and therefore probably does not justify screening for thyroid dysfunction in all patients with myasthenia gravis. The prevalence of thyroid autoantibodies in the serum of patients with myasthenia gravis has been described in many studies (16,17) to be higher (12–29%) than comparable

Table 2 Prevalence of Thyrotoxicosis/or Graves’ Disease (GD) in Myasthenia Gravis (MG) Reference

Prevalence (%)

Patients with MG (females)

Patients with MG and GD

16 7.6 91 (?) 7b 17 5.8 104 (68) 6 18 3.3 212 (125) 7 19 2.1 48 (32) 1 20 1.4a 74 (45) 1 Prevalence of thyrotoxicosis in the general population: 250 to 540 women/ 100,000; 0 to 210 men/100,000. Prevalence of thyrotoxicosis in MG: 1400 to 5800/100,000 a

This study could not find a significant difference in the prevalence of GD when comparing patients having MG with a gender- and age-matched control group. b Three of these patients had hyperthyroid GD, four had euthyroid GD.

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values of control populations (3–6%) (17,20,24). This relative increase, however, does not reach the level of significance in some studies (20). The occurrence of thyroid autoantibodies, moreover, does not necessarily identify patients who develop thyroid dysfunction because of autoimmune thyroid disease. Therefore, their routine measurement in myasthenia gravis patients without clinical signs of thyroid disease seems also of little prognostic help. Marino and colleagues (25) have found that myasthenia gravis associated with autoimmune thyroid disease (Graves’ disease and Hashimoto’s thyroiditis) has a mild clinical expression with preferential ocular involvement and lower frequency of thymic disease and of acteylcholine receptor antibodies. They suggest that concurrent ocular myasthenia gravis and endocrine ophthalmopathy may be due to immunological cross-reactivity against common autoimmune targets in the eye muscle as well as to a common genetic background. The findings of Spurkland et al. (7) substantiate the latter part of this hypothesis to a certain extent: they have pointed out that myasthenia gravis patients with concurrent thymoma tend to be less frequently positive for human leukocyte antigen (HLA)-B8 and DR 3 markers than their controls. Only patients with concomitant thymic hyperplasia had a relatively higher frequency of HLA B8 and DR3, a constellation typical for Graves’ disease. The percentage of patients with thymoma in Marino et al.’s (25) group with concurrent Graves’ disease and myasthenia gravis had indeed the lowest occurrence rate of thymoma (8.9% vs. 19.4% in control).

REFERENCES 1. Ko¨hler W, Sieb P. Myasthenia gravis. Bremen: UNI-MED Verlag AG, 2000:58–70. 2. Barton JJS, Fouladvand M. Ocular aspects of myasthenia gravis. Semin Neurol 2000; 20:7– 20. 3. Rennie GE. Exophthalmic goitre combined with myasthenia gravis. Rev Neurol Psychiatry 1908; 6:229–233. 4. Boyages SC. The neuromuscular system and brain in thyrotoxicosis. In: Braverman LE, Utiger RD, eds. Werner and Ingbar’s The Thyroid: A Fundamental and Clinical Text. 8th ed. Philadelphia: Lippincott Williams & Wilkins, 2000:631–633. 5. Farid NR, Stone E, Johnson G. Graves’ disease and HLA: clinical and epidemiologic associations. Clin Endocrinol 1980; 15:535–539. 6. Ragheb S, Lisak RP. The immunopathogenesis of acquired (autoimmune) myasthenia gravis. In: Lisak RP, ed. Handbook of Myasthenia Gravis and Myasthenic Syndromes. New York: Marcel Dekker, 1994:239–276. 7. Spurkland A, Gilhus NE, Ronnigen KS, Aarli JA, Vartdal F. Myasthenia gravis patients with thymus hyperplasia and myasthenia gravis patients with thymoma display different HLA associations. Tissue Antigens 1991; 37:90–93. 8. Osserman KE, Silver S. The differential diagnosis of myopathy as seen in hyperthyroidism and myasthenia gravis. In: Pitt-Rivers R, ed. Advances in Thyroid Research. Oxford: Pergamon Press, 1961:100–117. 9. Ohno M, Hamada N, Yamakawa J, Noh J, Morii H, Ito K. Myasthenia gravis associated with Graves’ disease in Japan. Jpn J Med 1987; 26:2–6. 10. Sahay BM, Blendis LM, Greene R. Relation between myasthenia gravis and thyroid disease. Br Med J 1965; 1:762–766. 11. Kuroiwa Y. Epidemiological aspects of myasthenia gravis in Japan. In: Japan Medical Research Foundation, eds. Myasthenia Gravis. Tokyo: University of Tokyo Press, 1981:9–20.

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12. Somnier FE, Keiding N, Paulson OB. Epidemiology of myasthenia gravis in Denmark. A longitudinal and comprehensive population survey. Arch Neurol 1991; 48:733–739. 13. Phillips LH. The epidemiology of myasthenia gravis. Neurol Clin 1994; 12:263–271. 14. Lavrnic D, Jarebinski M, Rakocevic-Stojanovic V, Stevic Z, Lavrnic S, Pavlovic S, Trikic R, Tripkovic I, Neskovic V, Apostolski S. Epidemiological and clinical characteristics of myasthenia gravis in Belgrade, Yugoslavia (1983–1992). Acta Neurol Scand 1999; 100:168–174. 15. Jacobson DM. Acetylcholine receptor antibodies in patients with Graves’ ophthalmopathy. J Neuroophthalmol 1995; 15:166–170. 16. Marino M, Barbesino G, Manetti L, Chiovato L, Ricciardi R, Rossi B, Muratorio A, Mariotti S, Braverman LE, Pinchera A. Mild clinical expression of myasthenia gravis associated with autoimmune thyroid disease—author’s response. Letter to the Editor. J Clin Endocrinol Metab 1997; 82:3905–3906. 17. Kiessling WR, Pflughaupt KW, Ricker K, Haubitz I, Mertens H-G. Thyroid function and circulating antithyroid antibodies in myasthenia gravis. Neurology 1981; 31:771–774. 18. Christensen PB, Jensen TS, Tsiropoulos I, Sorensen T, Kjaer M, Hojer-Pedersen E, Rasmussen MJ, Lehfeldt E. Associated autoimmune disease in myasthenia gravis. A population-based study. Acta Neurol Scand 1995; 91:192–195. 19. Thorlacius S, Aarli JA, Riise T, Matre R, Johnsen HJ. Associated disorders in myasthenia gravis: autoimmune diseases and their relation to thymectomy. Acta Neurol Scand 1989; 80: 290–295. 20. Weissel M, Mayr N, Zeitlhofer J. Clinical significance of autoimmune thyroid disease in myasthenia gravis. Exp Clin Endocrinol Diabetes 2000; 108:63–65. 21. Dos Remedios LV, Weber PM, Feldman R, Schurr DA, Tsoi TG. Detecting unsuspected thyroid dysfunction by the free thyroxine index. Arch Intern Med 1980; 140:1045–1049. 22. Eggertson R, Petersen K, Lundberg P-A, Nystrom E, Lindstedt G. Screening for thyroid disease in a primary care unit with a thyroid stimulating hormone assay with a low detection limit. Br Med J 1988; 297:1586–1592. 23. Vanderpump MPJ, Tunbridge WMG, French JM, Appleton D, Bates D, Clark F, Grimley Evans J, Hasan DM, Rodgers H, Tunbridge F, et al. The incidence of thyroid disorders in the community: a twenty year follow-up of the Whickham survey. Clin Endocrinol 1995; 43:55– 68. 24. Tunbridge WMJ, Evered DC, Hall R, Appleton D, Brewis M, Clark F, Evans JG, Young E, Bird T, Smith PA. The spectrum of thyroid disease in the community: The Whickham survey. Clin Endocrinol 1977; 7:481–493. 25. Marino M, Ricciardi R, Pinchera A, Barbesino G, Manetti L, Chiovato L, Braverman LE, Rossi B, Muratorio A, Mariotti S. Mild clinical expression of myasthenia gravis associated with autoimmune thyroid disease. J Clin Endocrinol Metab 1997; 82:438–443.

16 Pregnancy and Hyperthyroidism CORINNE R. FANTZ and ANN M. GRONOWSKI Washington University School of Medicine, St. Louis, Missouri, U.S.A.

Thyroid status in the pregnant patient is sometimes difficult to assess due to the normal physiological changes associated with pregnancy. This chapter outlines the changes that occur in normal pregnancy and discusses thyroid hyperfunction during pregnancy, in particular. A careful clinical evaluation of the patient’s history, symptoms, and laboratory measurements will help the physician correctly assess thyroid status. I.

REGULATION OF THYROID FUNCTION DURING NORMAL PREGNANCY

A. Transport Proteins Thyroid hormones circulate bound to three serum proteins: thyroxine-binding globulin (TBG), transthyretin, and albumin. TBG has a high affinity for thyroid hormones and despite low concentrations in the serum, it is responsible for the majority of T4 and T3 transport (1). During pregnancy, the binding affinities of the three transport proteins are not significantly altered. However, the circulating concentration of TBG more than doubles while the concentrations of transthyretin and albumin remain relatively unchanged (2–4). Serum TBG concentration increases rapidly in the first trimester, stabilizes in midgestation, and remains high until parturition (3). The increase in TBG is due to elevated concentrations of circulating estrogens during pregnancy, which are responsible for an increase in hepatic biosynthesis of TBG as well as an increase in TBG sialylation (2,4,5). Modification of TBG sialic acid content results in a decrease in metabolism and thus an extended half-life.

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Thyroid Hormones

Concentrations of circulating thyroid hormones, thyroxine and triiodothyronine, are increased in pregnancy largely due to the increase in TBG (4). Despite the maintenance of a euthyroid condition, TT4 and TT3 concentrations often exceed the normal reference intervals. Reflecting the increase in TBG, concentrations of TT4 and TT3 rise substantially in the first trimester, reach a plateau around midgestation, and remain constant throughout the remainder of the pregnancy (4). It has been proposed that increases in total thyroid hormones could also be due to the increased production of type III deiodinase. Maternal hormones cross the placenta and are converted from T4 and T3 to rT3 and T2, respectively, by placenta type III deiodinase, which has extremely high activity during pregnancy (6). It has been suggested that high turnover rates create an increase in demand for total thyroid hormones during pregnancy (7,8). It is generally accepted that concentrations of circulating free hormones are lower, albeit still within normal limits, than concentrations in nonpregnant women (9). There is some controversy about this in the literature (10–15); however, most recent publications suggest that the differences among published reports are likely due to the assays used to measure free hormones (16,17). It is important to note that this trend of lower concentrations of free hormones is more notable among women in iodine-deficient areas (18). C.

Thyroglobulin

Thyroid hormones are synthesized and stored in the colloid matrix of the thyroid follicles known as thyroglobulin (TG) (1). TG concentrations represent the activity and volume of the thyroid gland despite having no known hormonal function (19). In pregnancy, TG concentrations are often elevated, typically in the second and third trimesters, demonstrating increased thyroid stimulation (4). Increasing concentrations of TG are often associated with increases in thyroid volume (4). Although goiter is observed in fewer than 15% of pregnant women in the United States, women in iodine-deficient areas have significant increases in thyroid volume and hence elevations of TG (20,21). D.

Iodine Clearance

Circulating iodine concentrations are maintained in equilibrium with the iodine present in the thyroid and kidneys (4). In pregnancy, the glomerular filtration rate is considerably increased over nonpregnant patients, thereby resulting in lower concentrations of circulating iodine (22). The thyroid gland counteracts renal losses by increasing thyroidal iodine clearance, sometimes as much as two- to threefold over nonpregnant patients (23). Renal loss of iodine in areas of inadequate dietary supplies can rapidly lead to hypothyroidism and goiter, especially in the second and third trimesters of pregnancy when maternal iodine crosses the placenta in response to fetal demands (24). E.

Human Chorionic Gonadotropin

Human chorionic gonadotropin (hCG) and thyroid-stimulating hormone (TSH) belong to a family of heterodimeric glycoproteins that share a common α-subunit and differ only by a hormone-specific β-subunit (1). Extensive homology exists between TSH and hCG in the β-subunit and several conserved cysteine residues suggest similar three-dimensional structures (25). In addition, the luteinizing hormone (LH)/hCG and TSH receptors also share structural homology (25). Kosugi et al. demonstrated cross-reactivity of hCG to

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Figure 1 Serum TSH and hCG as a function of gestational age. Serum hCG was determined at initial evaluation and during late gestation. The data points represent the mean values (⫾SE) for samples pooled for 2 weeks of 33 determinations for hCG and 49 for TSH. (From Ref. 21.) TSH receptors that induces cellular responses leading to TSH suppression (26). Various reports indicate that the hCG in blood is a heterogeneous mixture and that certain oligosaccharide side chain modifications can affect the thyrotropic effect of hCG. For instance, removal of the sialic acid residues on hCG can increase its thyrotropic activity (27,28). Numerous studies have documented the thyrotropic effect of hCG (9,25,29–34). Approaching the end of the first trimester, when hCG concentrations are highest, hCG stimulates the thyroid to release thyroid hormones resulting in a transient suppression of TSH (Fig. 1) (21). In normal pregnancy TSH suppression is a transient phenomena that typically remains within normal reference limits. Abnormal values are only observed in cases when the hCG concentration exceeds 50,000 IU/L (4,9). In certain pathological conditions such as molar pregnancies and trophoblastic disease, circulating concentrations of hCG are extremely elevated for extended periods of time, and the thyroid stimulatory effects of hCG are more severe, often inducing thyroid hyperfunction (4). II. THYROID HYPERFUNCTION IN PREGNANCY A. Causes Graves’ disease, toxic multinodular goiter, subacute thyroiditis, toxic adenoma, TSH hypersecretion, and hormone overreplacement are just a few of the causes of hyperthyroidism occurring in the general population, although all of these can be observed in pregnant patients as well (35–38). Graves’ disease is by far the most common cause of hyperthyroidism in pregnancy (39,40). Hyperemesis gravidarum and hydatiform mole are pregnancy-specific associations that can induce hyperthyroidism and will be discussed

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below. The prevalence of hyperthyroidism complicating pregnancy has been estimated to be 0.1–0.4% and is presumed to be increasing (35,38). This rise has in part been due to increased physician awareness and increased sensitivity of assays in detecting mild forms of the disease. Although most pregnant women can tolerate mild hyperthyroidism, it is critical to monitor hyperthyroid patients. Poorly controlled hyperthyroidism in pregnancy can lead to deleterious effects in the mother and fetus (4). Some of these complications include congestive heart failure, thyroid storm, infection, spontaneous abortions, increased rate of stillbirths, low birth weights, preterm delivery, fetal or neonatal hyperthyroidism, and intrauterine growth retardation (37,39,40). Euthyroid pregnant women can exhibit tachycardia, wide pulse pressures, and mild heat intolerance that may make the diagnosis of hyperthyroidism difficult (39,41). However, a careful clinical interpretation of observed symptoms, medical history, and laboratory measurements can lead to the appropriate assessment of thyroid status. B.

Diagnosis and Laboratory Assessment

Differentiating between symptoms of hyperthyroidism and the hypermetabolic state of pregnancy can be particularly challenging. If symptoms such as weight loss or inappropriate weight gain, the presence of goiter, lid lag, fatigue, heart rate ⬎100 beats/min (bpm), onycholysis, and ophthalmopathy are observed, the clinical suspicion of hyperthyroidism should be evaluated (20). Laboratory testing is similar to that in nonpregnant patients and should include measurement of TSH and free, not total, hormone levels. As discussed earlier, total T4 and T3 measurements are influenced by fluctuations in serum TBG concentrations during pregnancy and therefore should not be used (2,4,41). Measurements of free concentrations can be determined either directly or by a calculated index. In spite of increases in TBG during pregnancy, calculated indices are useful in determining free concentrations. In addition, hyperthyroid patients may exhibit mild increases in certain routine laboratory tests including white blood count, calcium, bone alkaline phosphatase, and liver enzymes (42). Table 1 summarizes thyroid-related changes that occur during pregnancy (5). C.

Graves’ Disease and Pregnancy

Graves’ disease is the most common cause of hyperthyroidism in pregnant women, accounting for ⬎85% of all cases (20,43,44). Typically, a history of Graves’ disease or at least thyrotoxic symptoms predates the pregnancy. It is important to obtain a complete medical history and carefully evaluate clinical symptoms because a missed diagnosis can pose serious threats to the mother and fetus. Graves’ disease is characterized by the presence of goiter, tachycardia, warm moist skin, and mild heat intolerance (1). Ophthalmic findings suggestive of Graves’ include proptosis and diplopia resulting from eye muscle dysfunction (40). Exophthalmos is absent or mild, with one eye appearing slightly more prominent than the other in most cases. Stare is common, as is edema of the conjuctiva. However, pretibial myxedema is rare (35). Swollen eye muscles of Graves’ ophthalmopathy may be detected by ultrasonography when clinical symptoms are inconclusive upon routine examination (40). Unfortunately, the literature offers only a limited number of cases that discuss treatment and intervention methods for endocrine orbitopathy in pregnancy (45). The natural course of Graves’ disease is altered during pregnancy. There is an aggra-


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Table 1 Thyroid-Related Changes During Pregnancy Physiological change ↑ Serum estrogens ↑ Serum TBG ↑ hCG ↑ Iodine clearance ↑ Type III deiodinase ↑ Demand for T4 and T3

Resulting change in thyroid activity ↑ ↑ ↑ ↓ ↑ ↑ ↓ ↑ ↑ ↑ ↑ ↑ ↑

Serum TBG Demand for T4 and T3 total T4 and T3 TSH (in reference range unless hCG ⱖ 50,000 IU/L) f T4 (in reference range unless hCG ⱖ 50,000 IU/L) Dietary requirement for I2 Hormone production in I2 deficient areas Goiter in I2-deficient areas T4 and T3 degradation Demand for T4 and T3 Serum thyroglobulin Thyroid volume Goiter in I2-deficient areas

↑, elevated; ↓, reduced. Source: Modified from Ref. 25.

vation in the first trimester due to increased thyroid activity, amelioration in the second and third trimesters of pregnancy because of immunosuppression, and exacerbation of symptoms in the postpartum period as the immune system rebounds (46). Additional laboratory tests to differentiate Graves’ disease from other causes of hyperthyroidism include measurement of thyroid peroxidase antibodies (TPO) and thyroid hormone receptor antibodies (TSHR-abs) (5,47). TPO antibodies suggest an autoimmune cause and TSHR-abs are specific for Graves’ disease. Therefore, measurement of these antibodies can be useful in establishing a diagnosis of Graves’ disease. Furthermore, the TSHR-abs have prognostic implications for fetal and neonatal hyperthyroidism (39,42,48). TSHR-abs can cross the placenta and, at high concentrations, bind to TSH receptors and stimulate the fetal thyroid (49). High titers of TSHR-abs (⬎500% over normal) in maternal serum are predictive of fetal or neonatal dysfunction (20). It is important to note that a patient may be clinically euthyroid during pregnancy, but a previous history of Graves’ disease can result in a persistence of high concentrations of TSHR-abs (50). The fetus should be closely monitored for signs of TSHR-abs-stimulating activity. Ideally, women should have their hyperthyroidism under control prior to conception. Antithyroid drugs (ATDs) are the treatment of choice during pregnancy (37). The dosage should be titrated to achieve the minimum drug required to maintain the free thyroid hormone levels in the upper third of the normal range (38,51). ATDs can cross the placenta and therefore, their administration should be reduced or stopped whenever possible, for example, during the second and third trimesters when the symptoms of Graves’ disease begin to lessen (39,52). Subtotal thyroidectomy should only be performed if there is an allergic reaction to ATDs or if there is sufficient evidence for drug resistance (20). If surgery is deemed necessary, it should be postponed until after the first trimester (38). 131 I treatment is contraindicated in pregnancy (52). D. Thyroid Antibodies and Spontaneous Miscarriage One percent of women experience recurrent (three or more) spontaneous miscarriages (53,54). Only within the last decade has there been shown to be a strong association

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Figure 2 The percentage of miscarriages in unselected pregnancies in women who were thyroid antibody positive (TAb⫹) and thyroid antibody negative (TAb⫺). (From Ref. 53.)

between thyroid antibodies and recurrent abortions (54–59). Stagnaro-Green et al. were the first to recognize the correlation in their study that was initially designed to determine the prevalence and causes of postpartum thyroiditis (55). During the study, it was discovered that patients who were thyroid antibody positive (TPO and/or Tg) experienced a significantly greater number of miscarriages than women who were thyroid antibody negative. Four additional studies have confirmed this report (56–59). These findings are reviewed by Abramson et al. and summarized in Figure 2 (53). All of these studies demonstrate an association with positive thyroid antibodies and spontaneous miscarriage, although there was not a correlation with thyroid antibody titers and pregnancy loss. At this time the mechanism of pregnancy loss and its relationship to the presence of thyroid antibodies remains elusive. Research aimed at treatment intervention in at-risk patients is currently being evaluated. E.

Gestational Transient Thyrotoxicosis

Gestational transient thyrotoxicosis (GTT) is a broad term that encompasses a number of nonimmune causes for transient hyperthyroidism associated with pregnancy (4). Although the majority of cases of transient hyperthyroidism in pregnancy are affiliated with hyperemesis gravidarum, other conditions of pregnancy such as multiple gestation and gestational trophoblastic disease can result in transient hyperthyroidism with or without symptoms of hyperemesis. Therefore, some researchers have adopted the term transient hyperthyroidism of hyperemesis gravidarum (THHG) to define the most common syndrome of transient hyperthyroidism in pregnancy (60).


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Hyperemesis gravidarum occurs in about 0.2% of pregnant women and symptoms of hyperthyroidism manifest in more than half of those patients (60,61). These patients generally have no history of thyroid illness prior to pregnancy, goiter is usually absent, and thyroid antibodies are absent (4). Laboratory evaluation generally finds elevated concentrations of free T4, often over free T3 concentrations (5). Studies suggest that hyperemesis gravidarum is associated with extreme elevated concentrations of hCG in early pregnancy (62). In addition, desialylated forms of hCG have been isolated from serum of patients experiencing hyperemesis gravidarum (27,63). Although these patients frequently have more severe symptoms, there is not always a correlation between increased concentrations of hCG and symptoms of hyperemesis gravidarum (20). The symptoms associated with THHG typically disappear upon resolution of the hyperemesis. Gestational trophoblastic disease (GTD) is another nonimmune condition associated with transient hyperthyroidism of pregnancy (63,64). GTD is a general term that includes benign and malignant conditions of hydatidiform mole and choirocarcinomas. Goiter is rare or lacking in these patients and ophthalmopathy is absent (43). Hyperthyroidism in these patients is attributed to significant and sustained elevations in serum hCG concentrations, which in some cases exceed the upper limit of normal by 1000 times. Laboratory examination finds increases in free hormone concentrations and marked elevation in serum hCG levels (4). As is the case with hCG-induced stimulation, T4 to T3 ratio is commonly increased over ratios observed in patients with Graves’ disease (25). Treatment involves complete removal of the GTD and this rapidly cures the hyperthyroidism. F. Postpartum Thyroid Disease Postpartum thyroid disease (PPTD) is believed to be an autoimmune destruction of thyroid follicles that results in transient hyperthyroidism (1–3 months postpartum) followed by hypothyroidism (3–8 months postpartum) (65,66). PPTD occurs with a prevalence of approximately 5–9% in unselected postpartum women (66–68). The release of preformed T4 and T3 from the damaged thyroid makes this condition characteristically distinct from Graves’ disease (69). PPTD can be differentiated from Graves’ disease on the basis of low radioactive iodine or technetium uptake in the thyroid during the thyrotoxic phase. Serum TSH is a good screening test. If results are abnormal, measurement of free T4 should be performed. Despite the strong association of TPO antibodies with PPTD, 50% of TPO-antibody-positive women do not develop PPTD (66,67). Occasionally, antithyroglobulin (TG) antibodies are present and, in rare cases, anti-TG antibodies are the only antithyroid antibodies found (70). Although PPTD is a transient state of thyroid dysfunction, there is an increased risk for permanent hypothyroidism (71). Treatment is usually not required because symptoms of PPTD generally are mild and nonspecific. In fact, PPTD is often underdiagnosed (72). Patients with a history of unstable thyroid function should be monitored yearly to assess thyroid status for subsequent pregnancies and for the development of permanent thyroid dysfunction. III. SUMMARY Correct assessment of thyroid function during pregnancy is critical to avoid both fetal and maternal complications. It is also important to keep in mind that thyroid activity undergoes many changes during normal pregnancy including significant increases in serum TBG, thyroglobulin, total T4, and total T3; an increase in renal iodine clearance; and hCG stimu-

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lation. However, measurement of these values is not useful in the investigation of thyroid disease during pregnancy. Assessment of both hyper- and hypothyroidism should be done with a careful evaluation of the patient’s symptoms as well as measurement of TSH and free thyroid hormones. Measurement of thyroid autoantibodies may also be useful to diagnose maternal Graves’ disease, recurrent spontaneous miscarriages, and postpartum disease. Knowing the patient’s history, clinical symptoms, and, moreover, realizing the changes associated with thyroid function in pregnancy, the physician can properly determine thyroid status. REFERENCES 1. Larsen PR, Davies TF, Hay ID. The thyroid gland. In: Wilson JD, Foster DW, Kronenberg HM, Larsen PR, eds. Williams Textbook of Endocrinology. Philadelphia: WB Saunders, 1998: 389–515. 2. Ain KB, Mori Y, Refetoff S. Reduced clearance rate of thyroxine-binding globulin (TBG) with increased sialylation: a mechanism for estrogen-induced elevation of serum TBG concentration. J Clin Endocrinol Metab 1987; 65:689–696. 3. Skjoldebrand L, Brundin J, Carlstrom A, Pettersson T. Thyroid associated components in serum during normal pregnancy. Acta Endocrinol (Copenh) 1982; 100:504–511. 4. Glinoer D. The regulation of thyroid function in pregnancy: pathways of endocrine adaptation from physiology to pathology. Endocr Rev 1997; 18:404–433. 5. Brent GA. Maternal thyroid function: interpretation of thyroid function tests in pregnancy. Clin Obstet Gynecol 1997; 40:3–15. 6. Roti E, Fang SL, Green K, Emerson CH, Braverman LE. Human placenta is an active site of thyroxine and 3,3′,5-triiodothyronine tyrosyl ring deiodination. J Clin Endocrinol Metab 1981; 53:498–501. 7. Burrow GN, Fisher DA, Larsen PR. Maternal and fetal thyroid function. N Engl J Med 1994; 331:1072–1078. 8. Fisher DA, Polk DH, Wu SY. Fetal thyroid metabolism: a pluralistic system. Thyroid 1994; 4:367–371. 9. Guillaume J, Schussler GC, Goldman J, Wassel P, Bach L. Components of the total serum thyroid hormone concentrations during pregnancy: high free thyroxine and blunted thyrotropin (TSH) response to TSH-releasing hormone in the first trimester. J Clin Endocrinol Metab 1985; 60:678–684. 10. Boss M, Kingstone D. Serum free thyroxine in pregnancy. Br Med J 1979; 2:550. 11. Kurtz A, Dwyer K, Ekins R. Serum free thyroxine in pregnancy. Br Med J 1979; 2:550–551. 12. Yamamoto T, Amino N, Tanizawa O, Doi K, Ichihara K, Azukizawa M, Miyoi K. Longitudinal study of serum thyroid hormones, chorionic gonadotropin and thyrotropin during and after normal pregnancy. Clin Endocrinol 1979; 10:459–468. 13. Harada A, Hershman JM, Reed AW, Braunstein GD, Dignam WJ, Derzko C, Freidman S, Jewelewicz R, Pekary AE. Comparison of thyroid stimulators and thyroid hormone concentrations in the sera of pregnant women. J Clin Endocrinol Metab 1979; 48:793–797. 14. Malkasian GD, Mayberry WE. Serum total and free thyroxine and thyrotropin in normal and pregnant women, neonates and women receiving progestogens. Am J Obstet Gynecol 1970; 108:1234–1238. 15. Osathanondh R, Tulchinsky D, Chopra IJ. Total and free thyroxine and triiodothyronine in normal and complicated pregnancy. J Clin Endocrinol Metab 1975; 42:98–104. 16. Roti E, Gardini E, Minelli R, Bianconi L, Flisi M. Thyroid function evaluation by different commercially available free thyroid hormone measurement kits in term pregnant women and their newborns. J Endocrinol Invest 1991; 14:1–9. 17. Deam D, Goodwin M, Ratnaike S. Comparison of four methods for free thyroxin. Clin Chem 1997; 37:569–572.


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18. Glinoer D. Maternal and fetal impact of chronic iodine deficiency. Clin Obstet Gynecol 1997; 40:102–116. 19. Spencer CA, Wang C-C. Thyroglobulin measurement; techniques, clinical benefits, and pitfalls. Endocrinol Metab Clin North Am 1995; 24:841–863. 20. Mestman J, Goodwin TM, Montoro MM. Thyroid disorders of pregnancy. Endocrinol Metab Clin North Am 1995; 24:41–71. 21. Glinoer D, DeNayer P, Bourdoux P, Lemone M, Robyn C, van Steirteghem A, Kinthaert J, Lejeune B. Regulation of maternal thyroid during pregnancy. J Clin Endocrinol Metab 1990; 71:276–287. 22. Dafnis E, Sabatini S. The effect of pregnancy on renal function: physiology and pathophysiology. Am J Med Sci 1992; 303:184–205. 23. Pochin EE. The iodine uptake of the human thyroid throughout the menstrual cycle and in pregnancy. Clin Sci 1952; 11:441–445. 24. Thilly CH, Vanderpas JB, Bebe N, Ntambue K, Contempre B, Swennen B, Moreno-Reyes R, Bourdoux P, Delange F. Iodine deficiency, other trace elements, and goitrogenic factors in the etiopathogeny of iodine deficiency disorders (IDD). Biol Trace Elem Res 1992; 32: 229–243. 25. Goodwin TM, Hershman JM. Hyperthyroidism due to inappropriate production of human chorionic gonadotropin. Clin Obstet Gynecol 1997; 40:32–44. 26. Kosugi S, Mori T. TSH receptor and LH receptor. Endocrinol J 1995; 45:587–606. 27. Yoshimura M, Pekary AE, Pang XP, Berg L, Goodwin TM, Hershman JM. Thyrotropic activity of basic isoelectric forms of human chorionic gonadotropin extracted from hydatidiform mole tissues. J Clin Endocrinol Metab 1994; 78:862–866. 28. Mann K, Schneider N, Hoermann R. Thyrotropic activity of acidic isolectric variants of human chorionic gonadotropin from trophoblastic tumors. Endocrinology 1986; 118:1558–1566. 29. Yoshimura M, Hershman JM. Thyrotropic action of human chorionic gonadotropin. Thyroid 1995; 5:425–434. 30. Yoshikowa N, Nishikawa M, Horimoto M, Yoshimura M, Sawaragi S, Horikoshi Y, Sawaragi I, Inada M. Thyroid-stimulating activity in sera of normal pregnant women. J Clin Endocrinol Metab 1989; 69:891–895. 31. Yoshimura M, Hershman JM, Pang XP, Berg L, Pekary AE. Activation of the thyrotropin (TSH) receptor by human chorionic gonadotropin and leutinizing hormone in Chinese hamster ovary cells expressing functional human TSH receptors. J Clin Endocrinol Metab 1993; 77: 1009–1013. 32. Ball R, Freedman DB, Holmes JC, Midgley JEM, Sheehan CP. Low-normal concentrations of free thyroxin in serum in late pregnancy: physiological fact, not detected artifact. Clin Chem 1989; 35:1891–1896. 33. Tomer Y, Huber GK, Davies TF. Human chorionic gonadotropin (hCG) interacts directly with recombinant human TSH receptors. J Clin Endocrinol Metab 1992; 74:1477–1479. 34. Davies TF, Platzer M. hCG-induced TSH receptor activation and growth acceleration in FRTL5 thyroid cells. Endocrinology 1986; 118:2149–2151. 35. Mestman J. Perinatal thyroid dysfunction: prenatal diagnosis and treatment. Medscape Women’s Health 1997; 2:1–11. 36. Mestman JH. Severe hyperthyroidism in pregnancy. In: Clark SL, Cotton DB, Hand GDV, Phelan JP, eds. Critical Care Obstetrics. London: Blackwell Science, 1991:307–328. 37. Mestman JH. Hyperthyroidism in pregnancy. Endocrinol Metab Clin North Am 1998; 27: 127–149. 38. Glinoer D. Thyroid hyperfunction during pregnancy. Thyroid 1998; 8:859–864. 39. Masiukiewicz US, Burrow GN. Hyperthyroidism in pregnancy. Thyroid 1999; 9:647–652. 40. Hamburger JH. Diagnosis and management of Graves’ disease in pregnancy. Thyroid 1992; 2:219–224. 41. Lazarus JH. Treatment of hyper- and hypothyroidism in pregnancy. J Endocrinol Invest 1993; 16:391–396.

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42. Mestman JH. Hyperthyroidism in pregnancy. Clin Obstet Gynecol 1997; 40:45–64. 43. Bishnoi A, Sachmechi I. Thyroid disease in pregnancy. Am Fam Physician 1996; 53:215– 220. 44. Lazarus JH. Thyroid disease in relation to pregnancy: a decade of change. Clin Endocrinol 2000; 53:265–278. 45. Nu¨βgens Z, Roggenka¨mper P, Schweikert HU. Entwicklung einer endokrinen orbitopathie wa¨hrend einer schwangerschaft. Klin Monatsbl Augenheilkd 1993; 202:130–133. 46. Amino N, Tada H, Hidaka Y. Autoimmune thyroid disease in pregnancy. J Endocrinol Invest 1996; 19:59–69. 47. Fantz CR, Dagogo-Jack S, Ladenson JH, Gronowski AM. Thyroid function during pregnancy. Clin Chem 1999; 45:2250–2258. 48. Skuza KA, Sills IN, Stene M, Rapaport R. Prediction of neonatal hyperthyroidism in infants born to mothers with Graves disease. J Pediatr 1996; 128:264–268. 49. Wallace C, Couch R, Ginsberg J. Fetal Thyrotoxicosis: a case report and recommendations for prediction, diagnosis and treatment. Thyroid 1995; 5:125–128. 50. Cove DH, Johnston P. Fetal hyperthyroidism: experience of treatment in four siblings. Lancet 1985; 1:430–432. 51. Gardner DF, Cruikshank DP, Hayes PM, Cooper DS. Pharmacology of propylthiouracil (PTU) in pregnant hyperthyroid women: correlation of maternal PTU concentrations with cord serum thyroid function tests. J Clin Endocrinol Metab 1986; 62:217–220. 52. Mulder JE. Thyroid disease in women. Med Clin North Am 1998; 82:103–125. 53. Abramson J, Stagnaro-Green A. In our view ... Thyroid antibodies and fetal loss: an evolving story. Thyroid 2001; 11:57–63. 54. Matalon ST, Blank M, Ornoy A, Shoenfeld Y. The association between anti-thyroid antibodies and pregnancy loss. Am J Reprod Immunol 2001; 45:72–77. 55. Stagnaro-Green A, Roman SH, Cobin RH, El-Harazy E, Alvarez-Marfany M, Davies T. Detection of at-risk pregnancy by means of highly sensitive assays for thyroid antibodies. JAMA 1990; 264:1422–1425. 56. Glinoer D, Soto MF, Bourdoux P, Lejeune B, Delange F, Lemone M, Kinthaert J, Robijn C, Grun J-P, De Nayer P. Pregnancy in patients with mild thyroid abnormalities: maternal and neonatal repercussions. J Clin Endocrinol Metab 1991; 73:421–427. 57. Lejeune B, Grun J-P, De Nayer P, Servais G, Glinoer D. Antithyroid antibodies: underlying thyroid abnormalities and miscarriage or pregnancy-induced hypertension. Br J Obstet Gynaecol 1993; 100:669–672. 58. Singh A, Dantas ZN, Stone S, Asch R. Presence of thyroid antibodies in early reproductive failure: biochemical versus clinical pregnancies. Fertil Steril 1995; 63:277–281. 59. Iijima T, Tada H, Hidaka Y, Mitsuda N, Murata Y, Amino N. Effects of autoantibodies on the course of pregnancy and fetal growth. Obstet Gynecol 1997; 90:364–369. 60. Goodwin TM, Montoro M, Mestman JH. Transient hyperthyroidism and hyperemesis gravidarum: clinical aspects. Am J Obstet Gynecol 1992; 167:648–652. 61. Mazzaferri EL. Evaluation and management of common thyroid disorders in women. Am J Obstet Gynecol 1997; 176:507–514. 62. Goodwin TM, Montoro M, Mestman JH, Pekary AE, Hershman JM. The role of chorionic gonadotropin in transient hyperthyroidism of hyperemesis gravidarum. J Clin Endocrinol Metab 1992; 75:1333–1337. 63. Hershman JM. Hyperthyroidism induced by trophoblastic thyrotropin. Mayo Clin Proc 1972; 47:913–918. 64. Mizouchi T, Nishimura R, Derappes C, Taniguchi T, Hamamoto T, Mochizuki M, Kobata A. Structures of the asparagine-linked sugar chains of human chorionic gonadotropin produced in choriocarcinoma. J Biol Chem 1983; 258:14126–14129. 65. Amino N, Miyai KJ, Onishi T, Hashimoto T, Arai K. Transient hypothyroidism after delivery in autoimmune thyroiditis. J Clin Endocrinol Metab 1976; 42:296–301.


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17 Medical Treatment of Systemic Graves’ Disease JEFFREY I. MECHANICK Mount Sinai School of Medicine, New York, New York, U.S.A.

I.

INTRODUCTION

The management of Graves’ hyperthyroidism has evolved in recent years chiefly due to a better understanding of the underlying molecular immunology and an ‘‘evidence-based’’ approach to clinical controversies. Since patients with Graves’ disease can present with signs and symptoms of orbitopathy, the ophthalmologist must recognize the signs and symptoms of, as well as the treatment options for, the associated thyrotoxicosis. In this chapter, an evidence-based algorithmic approach to the medical management of Graves’ hyperthyroidism is discussed. In many patients, it is easy to diagnose Graves’ disease. The patient with a straightforward case will present with typical symptoms, signs, and thyroid function test results consistent with hyperthyroidism. Antibody titers to the thyroid-stimulating hormone (TSH) receptor will be elevated and radioiodine uptake will often be abnormally high. However, in some patients, critical data may be lacking or equivocal, in which case additional testing must be obtained and/or observation recommended while the disorder evolves. The patient may even present with overt orbitopathy without systemic manifestations of Graves’ disease; this is referred to as ‘‘euthyroid Graves’ disease.’’ When Graves’ hyperthyroidism has been established, therapy proceeds in two phases: early-phase therapy to control symptoms and reduce circulating levels of thyroid hormone (usually 1–6 weeks), and definitive therapy to prevent recurrence. Herein lies the most controversial aspect of management: should definitive treatment be with surgery, radioactive iodine (RAI), or antithyroid drugs (ATD)? Notwithstanding certain circumstances in which one modality is clearly indicated over the others, in the average patient,

155

a

Adapted from Ref. 2.

Surgery

Radioiodine therapy

Definitive therapy in the elderly or those with cardiac disease who refuse RAI True thyroid storm refractory to medical therapy Very large, symptomatic goiter Nodule suspicious for thyroid cancer Cosmesis desired by patient Pregnancy/breast feeding and allergy/adverse reaction to ATD Any patient who cannot or will not be treated with ATD or RAI

Early-phase management Accelerated hyperthyroidism Pre-RAI or surgery in the elderly or those with cardiac disease Patient refuses RAI and surgery Pregnancy/breast feeding and not a surgical candidate or refuses surgery Pregnancy planned within 4–6 months and not a surgical candidate or refuses surgery Definitive therapy in the elderly or those with cardiac disease, and not a surgical candidate or refuses surgery Allergy/adverse reaction to ATD and not a surgical candidate or refuses surgery Poor adherence to medical therapy and not a surgical candidate or refuses surgery

Clear indications

Treatment Options for Graves’ Hyperthyroidism

Antithyroid drugs

Modality

Table 1

Theoretically treats underlying autoimmunity Does not worsen orbitopathy Improvement in 2–4 weeks in 90% (2) Con: Minor adverse effects 5% (2) Major adverse effects 1% (fatalities very rarely) (2) Long-term therapy needed in children Recurrence rate could be as high as 70% (2) May require more frequent physician visits and lab work Pro: Minimal adverse effects (⬍ 1%) Low recurrence rate depending on dosage (5-20%) Con: Subjective, unproven, fears of radiation Likelihood of hypothyroidism 10–30% in first 2 years; 5%/year thereafter (2) Contraindicated with pregnancy and breast feeding Pregnancy should be deferred for 4–6 months after therapy Short-term worsening of orbitopathy, can be prevented with glucocorticoids Theoretical risk of cancer in children Radiation precautions following therapy Destructive Pro: Recurrence only 0.7–9.8% (3) Definitive pathology if nodule also present Con: Perceived risk although mortality virtually zero, permanent cord paralysis in 0–3.4% (3), permanent hypoparathyroidism in 0–2.8% (3) Cosmetic effect of neck wound May worsen orbitopathy but studies have also shown no effect or improvement in orbitopathy (3) More expensive than RAI and ATD (although long-term ATD may be more costly) Pain Permanent hypothyroidism in 20–50% (8) Destructive

Pro:

Subjective biasesa

156 Mechanick

Medical Treatment

157

many subjective biases must be fully discussed and priority given to patient preferences over individual physician experience and interpretation of the literature (2,3; Table 1). Practice guidelines for the management of Graves’ disease by the American Association of Clinical Endocrinologists (AACE), the American Thyroid Association (ATA), the American College of Physicians (ACP), and the Royal College of Physicians (RCP) were reviewed by Arbelle and Porath (4): both AACE and ATA prefer radioiodine therapy, RCP does not specify a preference, and ACP does not discuss a preference. Results from surveys of the ATA and European Thyroid Association (ETA) demonstrate a preference by European thyroidologists for the use of medical therapy and American thyroidologists for the use of radioiodine therapy (5–8). In a recent review on the subject, Weetman (2) advocates ATDs for patients under age 50 and RAI if the patient is age 50 or over, since recurrent hyperthyroidism is associated with a higher risk of atrial fibrillation in this age group; or if there has been a recurrence after ATD therapy, provided there is no indication for surgery. If ATDs are chosen for definitive therapy, there are still several decisions to be made: duration of therapy, high-dose (so-called block–replace) or low-dose (titration) therapy, choice of specific ATD, use of adjunctive therapy, and use of adjunctive diagnostic tests. Other questions include whether or not ATDs should be administered prior to RAI therapy and whether ATDs are safe for children and adolescents.

II. MEDICAL ARMAMENTARIUM A. Antithyroid Drugs The endocrinologist may individualize therapy using one or more drugs that influence thyroid pathophysiology (Table 2). The regimen will depend on symptom severity, medical comorbidities, patient’s age, and child-bearing status. The mainstays of treatment are the thionamides propylthiouracil (PTU) and methimazole (MMI). Carbimazole is principally used in Europe; 10 mg is rapidly converted to roughly 6 mg MMI in the serum. Since their pharmacological properties are virtually the same, they may be considered the same. Following the clinical studies by Astwood in 1943 (9) and Gabrilove et al. in 1945 (10) with thiouracil that demonstrated not only benefit but also a high frequency of agranulocytosis, PTU was synthesized and accepted. MMI was developed later and differs from PTU in several ways. Both drugs essentially inhibit the organification process, coupling reaction, thyroglobulin immunoreactivity, thyroidal autoimmunity, and thyroid cell growth. PTU, but not MMI, inhibits peripheral deiodination of T4 to T3, which may add benefit to the management of accelerated hyperthyroidism. However, a greater percentage of patients have disease that is controlled with a single daily dose of MMI than with PTU, favoring the use of MMI in patients with difficulty adhering to their regimen (11). Even though MMI has far greater lipid solubility than PTU, recent studies have demonstrated comparable fetal hypothyroidism and thus transplacental passage between PTU and MMI (12). However, excretion of MMI into breast milk exceeds that of PTU and the latter is generally recommended in nursing mothers when thionamide use is indicated (13). Adverse effects are comparable with PTU and MMI. If a hypersensitivity reaction occurs, generally after 3 weeks of therapy, it is reasonable to switch to the other thionamide before abandoning antithyroid medication. Agranulocytosis represents the major risk of this therapy and may be more frequent with higher doses and in older patients. To be eligible for ATD treatment, patients must understand

100–200 mg po TID

10–40 mg po qD

10–40 mg po QID 1–2 gtts po qD–TID 2–5 gtts po qD–TID 1–2 mg po BID–QID 40–60 mg po qD 0.5–3.0 gm po qD 300–450 mg po TID 4 gm po QID 5 gm po QID

Propylthiouracil

Methimazole

Propranolol

Potassium iodide

Sodium iodide (Lugol’s)

Dexamethasone

Prednisone

Ipodate

Lithium

Cholestyramine

Colestipol

Inhibits enterohepatic T4/T3 recirculation Inhibits enterohepatic T4/T3 recirculation

Inhibits hypermetabolism Inhibits deiodination Inhibits organification Inhibits T4/T3 release Inhibits organification Inhibits T4/T3 release Inhibits deiodination Expands plasma volume Inhibits deiodination Expands plasma volume Inhibits T4/T3 release Inhibits deiodination Inhibits T4/T3 release

Inhibits organification Immunoregulation

Inhibits organification Immunoregulation Inhibits deiodination

Action

Po, by oral administration; qD, per day; TID, three times daily; QID, four times daily.

Usual starting dosage

Strategy and options

Short-term (1–2 weeks) for severe hyperthyroidism

Short term (1–2 weeks) with accelerated thyrotoxicosis or prior to surgery Alternative to stable iodine therapy especially before and after radioiodine therapy when ATD cannot be used Short-term (1–2 weeks) for severe hyperthyroidism

Short term (1–2 weeks) for severe hyperthyroidism

Continue high dosage for 6–18 months and add l-thyroxine to maintain euthyroidism and low–normal TSH level Titrate dosage down to 50 mg po qD–BID to maintain euthyroidism and low–normal TSH level Continue high dosage for 6–18 months and add l-thyroxine to maintain euthyroidism and low-normal TSH level Titrate dosage down to 2.5–5 mg po qD to maintain euthyrodism and low–normal TSH level Titrate to maintain HR in 70–80 bpm range; can usually stop once patient euthyroid; use diltiazem 120 mg po TID for bronchospasm Short-term (1–2 weeks) with accelerated thyrotoxicosis or prior to surgery Short-term (1–2 weeks) with accelerated thyrotoxicosis or prior to surgery Short-term (1–2 weeks) for severe hyperthyroidism

Dosing Regimens for Agents Used to Treat Graves’ Hyperthyroidism

Drug

Table 2

158 Mechanick

Medical Treatment

159

the importance of contacting their physician if they experience sore throat, unexplained fever, other signs of infection, generalized aching or malaise, rash, or pruritus. If these symptoms or signs occur, a complete blood count should be obtained immediately. Since agranulocytosis can occur suddenly, and many patients with Graves’ disease are leukopenic at presentation, it is not cost-effective to monitor the blood count routinely. If the leukocyte count is less than 1500–2000/mm3 or the granulocyte count less than 1000/ mm3, the patient should be admitted to the hospital for intravenous (IV) fluids and broadspectrum antibiotics; the ATD should be stopped and not restarted. The use of rh granulocyte colony-stimulating factor (GCSF) has been supported by several clinical studies (14– 16) but also refuted by a recent report by Fukata et al. (17) using prolonged doses. Until these negative findings are confirmed, a brief ambulatory course of rhGCSF is warranted since hospitalization may be avoided if the granulocyte count significantly rises hours after administration. Last, cholestatic hepatitis with MMI, and fulminant hepatic failure with PTU requiring liver transplant, have been reported. Hyperthyroidism itself is associated with abnormal liver function tests, but routine liver function monitoring for deteriorating function seems prudent. Once a particular ATD has been selected, a decision should be made whether to treat briefly to render the patient euthyroid and then administer radioiodine, or to continue the ATD as definitive therapy for 6–18 months. Several studies have reported higher overall remission rates with ATD (40–70%) (18–22) compared with beta blockers alone (14–30%); (23–26). In 1983, Romaldini et al. (27) demonstrated a relationship between daily doses of ATD (MMI and PTU) and remission rates in a retrospective, nonrandomized cohort study. In a prospective, randomized study in 1990, Allannic et al. (28) demonstrated a higher recurrence rate with a 6 month MMI course (58%) than with an 18 month MMI course (38%). Two prospective trials taken together suggest, but do not prove, a role for dietary iodine in recurrence rates following ATD therapy. In 104 patients from an iodine-deficient region, Meng et al. (29) found a relatively low 1 year recurrence rate: 31% and 33% following 40 mg or 5–10 mg MMI daily, respectively. In contrast, in patients from an iodine-rich region, Jorde et al. (30) found a relatively high 2 year recurrence rate: 72.4% and 81.5% following 60 mg or titrated low-dose MMI daily, respectively. Overall, retrospective studies have identified the following as good prognosticators for treatment with ATD: female ⬎ male, older age, smaller goiter or from an iodine-deficient region (decreased intrathyroidal iodine content), milder thyrotoxicosis, and lower TRAb levels (8,31–33). In fact, it is argued that monitoring TRAb titers may allow for an abbreviated (6 month) course of ATD by predicting long-term remissions (34). If used as definitive therapy, should high doses of ATD be used to ensure intrathyroidal levels necessary for immunosuppression? If so, supplemental l-thyroxine may need to be added to maintain euthyroidism and a low-normal TSH, thus avoiding physiological stimulation of thyroid cell growth and possible antigen expression. The recent literature has clarified some of these points. If the titration method is used (low-dose ATD), there is no benefit extending the treatment duration past 18 months (35). As an alternative, if the block–replace method is used (high-dose ATD), there may be no benefit beyond 6 months (36). A review of prospective, randomized controlled clinical trials comparing low- and high-dose ATD is given in Table 3. A critical review of these reports, heavily biased by the recent European Multicenter Trial (43), would conclude that there are insufficient data to justify routine use of the block–replace method.

Weetman et al. (1994) Edmonds/Tellez (1994) Iriarte et al. (1995)

Tamai et al. (1995) Mclver et al. (1996) Benker et al. (1998)

36 39 40

41 42 43

195 53 313

100 70 66

309

109

N

12 18 12

6 vs. 12 12 24

12

12

12 3–18 51 ⫾ 16

12 24 36

12

36

Follow-up (months) Conclusions

40 mg MMI controlled hyperthyroidism sooner than a 10 mg dose but with higher rate of adverse effects and no difference in 1 yr recurrence rates (36–37%) No advantage 12 months high-dose carb over 6 months No difference in recurrences with carb High-dosage carb had lower recurrence at 1 but not 3 yr All patients with large goiter had recurrences No difference in TSHR-ab by 2 yrs or recurrences by 3 yr with MMI No difference in TSHR-ab or recurrences with carb Longer follow-up of Reinwein et al. (1993) cohort above No difference in recurrences with MMI (58%) and no predictors identified

Decreased TSHR-ab and recurrence rate with high-dosage MMI

MMI, methimazole; PTU, propylthiouracil; carb, carbimazole; TSHR-ab, TSH receptor antibody.

38

Hashizume et al. (1991) Reinwein et al. (1993)

Authors (yr)

37

Reference

Duration of treatment (months)

Prospective, Randomized, Controlled Clinical Trials Comparing Low- and High-Dose ATD with Varying Treatment and Follow-Up Durations in Graves’ Disease

Table 3

160 Mechanick

Medical Treatment

B.

161

Adjunctive Medical Therapy

The goal of early-phase therapy in Graves’ disease is twofold: to decrease synthesis and release of thyroid hormone, and to lessen the impact of thyrotoxicosis on peripheral tissues. Antithyroid drugs act to decrease synthesis and, in the particular case of PTU, to decrease peripheral T4 to T3 conversion. However, several other classes of drugs can potentiate the effects of ATD. In cases in which ATD cannot be used because of adverse effects, these adjuvant agents can control thyrotoxicosis sufficiently until definitive therapy with radioiodine or surgery can be undertaken. 1. Adrenergic Antagonists and Calcium Channel Blockers Nonspecific clinical findings in thyrotoxicosis thought to derive from hyperadrenergic tone and improve with beta-blockade include fine tremor, palpitations, amenorrhea, stare, lid lag, heat intolerance, and anxiety (44). Clinical studies have failed to demonstrate conclusively any increased adrenergic sensitivity, adrenomedullary activity, or increased catecholamine levels with thyrotoxicosis. Therefore, the utility of beta-blockade is simply to inhibit native sympathetic tone on the heart and peripheral tissues. An additional favorable pharmacological effect of beta-blockers is the inhibition of 5′-monodeiodinase activity, which converts T4 to T3. Miscellaneous actions of beta-blockers are improvement in nitrogen balance, correction of hypercalcemia, reversal of bulbar dysfunction and proximal myopathy, and treatment of periodic paralysis. The usual starting dosage of propranolol is 10–40 mg orally four times daily, depending on the severity of the thyrotoxicosis. The dosage is titrated to achieve a heart rate in the 70–80 beats/min range and is gradually decreased as thyroid hormone levels normalize with ATD. Patients with a history of asthma may be treated with a calciumchannel blocker such as diltiazem. 2. Stable Iodine Even though iodine can cause hyperthyroidism in patients with nodular goiters, it can temporarily control hyperthyroidism in patients with Graves’ disease. The spectrum of action of iodides includes inhibition of trapping with prolonged exposure, inhibition of organification (Wolff-Chaikoff effect), inhibition of thyroid hormone release via TSH action on adenyl cyclase and thyroglobulin endocytosis, direct cytotoxicity, and inhibition of cellular proliferation and γ-interferon-induced major histocompatibility complex (MHC) class II expression. Overt improvement in the thyrotoxic patient occurs within days: 50% reduction in T4 by 4 days, and 47% reduction in T3 by 11 days (45,46). Escape occurs by 3–4 weeks as the trapping mechanism recovers and intrathyroidal iodine accumulation enhances total thyroid hormone secretion. One drop of saturated solution of potassium iodide (SSKI) equals 6 drops of compound solution of iodine (Lugol’s solution) and 38 mg iodine. The daily requirement is 75–200 µg (250 µg in pregnancy) and total body stores are 20–50 mg. Only a few drops per day are required for therapeutic action. Because of the very unpalatable taste, iodine should be diluted in 50–100 ml water prior to ingestion. Adverse effects range from acute hypersensitivity reactions (angioedema, hemorrhagic skin lesions, and serum sickness) to chronic iodism (brassy taste, burning mouth, parotid/salivary gland swelling, rhinitis, conjunctivitis, headache, cough, gastritis, bloody diarrhea, anorexia, depression, acneiform rash, and severe skin eruptions). Urinary iodine excretion can be promoted by administration of loop diuretics if a severe reaction occurs.

162

Mechanick

3. Glucocorticoids These drugs are very effective in the management of thyrotoxicosis because of their multiplicity of effects. Glucocorticoids inhibit peripheral monodeiodination of T4 into T3 as well as possibly decreasing thyroidal T4 output. If steroids with mineralocorticoid action are used, the plasma volume expands, which further reduces thyroid hormone concentrations. The use of dexamethasone 1–2 mg two to four times daily, or equivalent doses of prednisone or methylprednisolone, should be reserved for rapid biochemical control during early-phase therapy. H2-blockers, antacids, or proton-pump inhibitors might be useful to control the dyspepsia that may result from steroid use. If acute behavioral changes occur, the steroid should be discontinued. Fluid retention, alkalosis, and hypokalemia may result when steroids with intrinsic mineralocorticoid activity are used. Moreover, the possibility of hyperglycemia should be anticipated and treated if it develops. 4. Oral Cholecystographic Agents Ipodate is the most potent oral cholecystographic agent used to manage acute thyrotoxicosis. It is 63% iodine by weight, which explains part of its action. The liberated iodine acts to inhibit thyroid hormone release. An additional effect is inhibition of peripheral monodeiodinase activity. In hyperthyroid patients, the serum T3 level is reduced by 50– 62% in 24 h following a single 0.5, 1, or 3 g dose; after 6 h, there is a 30% reduction in serum T3 following a 3 g dose (47). This compares with a 65% reduction in serum T3 in 24 h following large and repeated doses of PTU, SSKI, and dexamethasone (48). Ipodate improves the biochemical response when added to an ATD regimen (49). It is superior to stable iodine due to the additional inhibitory effect on peripheral monodeiodination (75% reduction in T3 by day 5 for ipodate compared with 64% by day 9 for stable iodine; [50]). However, there is a rebound effect in serum T4 (23%) and T3 (50%) levels with ipodate discontinuation that is not seen with stable iodine discontinuation (50). Ipodate therapy may be considered for acute management of accelerated Graves’ hyperthyroidism. However, it should only be used for a brief period of time since iodine stores in fat can persist up to a year, compromise the efficacy of ATD, and therefore increase recurrence rates after ATD treatment is stopped (51). Adverse effects of ipodate include nausea, vomiting, and diarrhea as well as iodine-induced hyperthyroidism (Jod-Basedow phenomenon), which can also be observed with stable iodine treatment. 5. Lithium In 1968, Schou et al. (52) noted that patients treated with lithium for 5 months to 2 years developed goiter. Unlike stable iodine or ipodate, the use of lithium during early-phase management does not mitigate the efficacy of radioiodine therapy. When lithium levels are maintained at 0.5–1.0 mEq/L, with a usual daily dosage of 900–1500 mg, colloidal droplet formation and thyroglobulin hydrolysis, in response to TSH and cAMP, are inhibited. Following 2 weeks of lithium therapy, 8 of 11 Graves’ disease patients were rendered euthyroid; this was associated with a 35% reduction in serum T4 and T3 levels (53). During 6 months of treatment there was no escape, but after 1–4 weeks following discontinuation of the lithium, seven of the eight responders relapsed. This relapse can be prevented by concomitant use of ATD, which would inhibit thyroid hormone synthesis. Lithium is rapidly absorbed by the gastrointestinal tract and attains peak levels by 4 h, with a serum half-life of 24–36 h. There is 80% resorption in the proximal nephron and toxicity is dose-dependent. A three times daily regimen is preferred to produce an

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even plateau. Nevertheless, levels must be meticulously monitored and maintained in the 0.5–1.5 mEq/L range (60 years old and under) or 0.1–0.5 mEq/L (over 60 years old). Adverse effects of lithium are significant and account for the relative infrequency of its use in the management of thyrotoxicosis. Common side effects include nausea, diarrhea, anorexia, and malaise. Of interest, lithium therapy has been associated with progression of orbitopathy requiring surgical decompression, with lithium withdrawal inducing a dramatic improvement in the exophthalmos (54). Endocrinopathies associated with lithium use include hypothyroidism, hyperthyroidism (TSH receptor mediated in susceptible individuals), nephrogenic diabetes insipidus (managed with thiazides or amiloride), and hypercalcemia. 6. Bile Acid Sequestrants This class of drugs represents the newest addition to the armamentarium used to combat endogenous thyrotoxicosis. Both cholestyramine and colestipol bind iodothyronine from the enterohepatic circulation, thereby increasing their fecal excretion. They were first used to treat factitious or iatrogenic thyrotoxicosis due to inadvertent or surreptitious ingestion of excessive thyroid hormone. In a small controlled trial, cholestyramine, 4 g orally administered four times daily, improved the biochemical response to treatment with MMI (55). Similarly, but in a large, controlled trial of 92 patients, colestipol, 5 g orally four times daily, improved the biochemical response to treatment with MMI; the data indicated that MMI dosing could be reduced with colestipol, thus decreasing the risk of MMI-dependent side effects (56). These agents are generally safe but require that the patient can tolerate oral or enteric tube administration. Since the absorption of other drugs may be compromised if they are administered with the bile acid sequestrant, it is recommended that all other medications be taken approximately 2 h before or after cholestyramine or colestipol. III. SPECIAL CLINICAL SITUATIONS A. Pediatric Graves’ Disease Children and adolescents with Graves’ disease, in contrast to adults, present with weight loss, increased bowel movements, polyuria and polydipsia, palpitations, impaired skeletal mineralization, behavioral disturbances, and poor academic performance. In children treated with ATD, long-term remission rates range from 30 to 60%, with a longer time to remission in prepubertal children than in pubertal children (57). The initial PTU dosage in children is 5–10 mg/kg/day and 0.5–1.0 mg/kg/day MMI. Adverse effects of ATD are more common in children than adults: overall 35%; prepubertal 71%, pubertal 28%, postpubertal 25% (57). In a study of more than 500 children, the most common complication of ATD was mild liver function test elevation (28%), followed by mild leukopenia (25%), skin rash (9%), granulocytopenia (4.5%), arthritis (2.4%), nausea (1.1%), and agranulocytosis and hepatitis (0.4% each) (58). Surgery affords a rapid and definitive cure but, in addition to the infrequent risks of damage to the recurrent laryngeal nerve, hypoparathyroidism, and hypothyroidism, cosmesis is a concern. On ther other hand, radioiodine, despite being convenient and effective, is associated with a higher risk of thyroid cancer, especially in children under 5 years of age (58). Based on the available evidence, antithyroid drugs are a reasonable first-line choice for definitive therapy in older children and adolescents, and may be considered in younger children. The best approach involves a thorough discussion of the risks

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Mechanick

and benefits of these three efficacious modalities with the patient (if old enough) and parents. B.

Pregnancy, Postpartum, and Breast Feeding

Graves’ hyperthyroidism is the most common cause of thyrotoxicosis among pregnant women (see Ref. 59 for a review). Not infrequently, the diagnostic differentiation between physiological suppression of TSH and true hyperthyroidism is confusing. In fact, over half the patients with hyperemesis gravidarum in early pregnancy will have biochemical hyperthyroidism which will resolve by 18 weeks of gestation. Radioiodine scanning and treatment are absolutely contraindicated during pregnancy. Antithyroid drugs are used in early-phase therapy: PTU is generally preferred over MMI due to demonstration of less transplacental passage, although this concept has been challenged. In fact, in a retrospective study of 185 pregnant patients with Graves’ disease treated with ATD, PTU and MMI were equivalent with respect to percentage still hyperthyroid at delivery, time to euthyroidism, and incidence of major congenital anomalies (60). ATD are generally administered in smaller amounts in pregnancy. Initial dosages of PTU may be 100–200 mg daily and MMI 10–20 mg daily. Block–replace regimens of ATD therapy are contraindicated since they require higher dosages that can cause fetal hypothyroidism. If the patient’s disease cannot be controlled due to adverse effects of ATD or nonadherence to the medical regimen, surgery is indicated and generally performed in the second trimester when the hyperthyroidism ameliorates transiently. Beta-blockers may be safely used preoperatively or to control maternal symptoms of thyrotoxicosis, if severe, but there are controversial associations with placental insufficiency, intrauterine growth retardation, excessive uterine irritability, fetal bradycardia, hypoglycemia, hyperbilirubinemia, and polycythemia. Stable iodine can be used preoperatively, generally for less than 7–10 days to avoid fetal goiter. If accelerated hyperthyroidism occurs, especially during the onset of labor, dexamethasone, 2 mg every 6 h, may be added to the regimen. Up to 60% of women of reproductive age with Graves’ disease identify a postpartum onset (see 61 for review). This condition is associated with recurrent TSH-receptor antibodies and the appearance of symptoms 3–6 months after delivery. If ATD are chosen, low-dose PTU (⬍100–150 mg daily) is preferred because of its lower concentration in milk compared with MMI. If PTU allergy occurs, MMI can be used at dosages less than 10 mg daily. In any case, the baby should have thyroid function tests regularly to determine whether there is fetal hypothyroidism from ATD use, or fetal hyperthyroidism from transplacental passage of stimulating TSH-receptor antibodies (1–5% incidence). C.

Adjunctive Medical Therapy with Radioiodine Therapy or Surgery

Pretreatment with ATD may render the patient euthyroid more rapidly and decrease the risk of toxic radiation thyroiditis and accelerated hyperthyroidism. There has been little controversy surrounding the benefit of stopping ATD therapy during RAI therapy (62). However, the general practice of pretreating with PTU or MMI, discontinuing ATD at least 3 days prior to RAI, restarting ATD no sooner than 3 days following RAI, and then stopping ATD approximately 2 months after RAI, has recently been challenged. Tuttle et al. (63) demonstrated a higher failure rate when PTU was used as a pretreatment. In a prospective, randomized, controlled study of 51 patients with Graves’ disease, patients pretreated with MMI experienced higher post-RAI thyroid hormone levels due to with-

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drawal of the ATD than patients not pretreated at all (64). In a commentary by Perros (65), it is argued that pretreatment with ATD as early-phase therapy should only be reserved for those with severe thyrotoxicosis or heart disease. If early-phase medical therapy is required prior to RAI therapy, other drugs can be added to ATD to improve clinical and biochemical control. Administration of stable iodine initiated 7 days after RAI renders a euthyroid state earlier but with a more likely transient (60%), but not permanent (58%), post-RAI hypothyroid state (66). If the thyroid gland is small with rapid turnover, or if the patient is young and a lower radioiodine dosage is preferred, pretreatment for 7 days and posttreatment for 7 days with lithium can increase RAI dose retention (54). Propranolol and glucocorticoids can also provide additional control of severe thyrotoxicosis prior to RAI therapy. Prednisone, 0.4–0.5 mg/kg/day, or dexamethasone at equivalent dosages, initiated at the time of RAI therapy, continued for 1 month, and then weaned over a 2 month period, can attenuate the mild transient worsening of orbitopathy observed following RAI therapy (67). Subtotal thyroidectomy by an experienced thyroid surgeon is indicated for patients with Graves’ disease in whom immediate biochemical control is desired, the goiter is very large, or when there is a coexistent thyroid nodule that has a higher risk of malignancy than in patients without Graves’ disease. Contrary to destructive therapy with RAI, neartotal thyroidectomy is not associated with progression of orbitopathy (68). Preoperative therapy with ATD is recommended to render the patient euthyroid. Stable iodine may also be used for 1–2 weeks preoperatively to decrease blood flow and induce involution, firmness and mobility of the gland, thus technically facilitating the resection. If ATD or stable iodine cannot be used, an alternative would be lithium therapy. Propranolol is used pre- and postoperatively; shorter acting beta-blockers such as esmolol may be used intraoperatively.

IV.

CONCLUSION

The medical management of systemic Graves’ disease includes a host of drugs with specific and sometimes overlapping modes of action that allow for a tailoring of therapy. Antithyroid drugs are the mainstay of medical treatment and may be used as definitive therapy or in short courses prior to surgery or administration of radioiodine. Many disturbing controversies are being clarified by recent, well-designed clinical trials allowing an evidence-based approach. Future interventions will no doubt involve immunological methods directed at the autoimmune causes of Graves’ disease.

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6. Solomon B, Glinoer D, Lagasse R, Wartofsky L. Management of hyperthyroidism due to Graves’ disease: results of a survey of members of the ATA. 63rd Annual Meeting of the American Thyroid Association, Montreal, September, 1988. 7. Glinoer D, Hesch D, Lagasse R, Laurberg P. The management of hyperthyroidism due to Graves’ disease in Europe in 1986. Results of an international survey. 15th Annual Meeting of the European Thyroid Association, Stockholm, June–July, 1986. 8. Mechanick JI, Davies TF. Medical management of hyperthyroidism: theoretical and practical aspects. In: Falk SA, ed. Thyroid Disease: Endocrinology, Surgery, Nuclear Medicine, and Radiotherapy. Philadelphia: Lippincott–Raven, 1997:253–296. 9. Astwood EB. Treatment of hyperthyroidism with thiourea and thiouracil. JAMA 1943; 122: 78–81. 10. Gabrilove JL, Kert MJ, Soffer LJ. The use of thiouracil in the treatment of patients with hyperthyroidism. Ann Intern Med 1945; 23:537–558. 11. Gwinup G. Prospective randomized comparison of propylthiouracil. JAMA 1978; 239:2457– 2459. 12. Momotani N, Noh JY, Ishikawa N, Ito K. Effects of propylthiouracil and methimazole on fetal thyroid status in mothers with Graves’ hyperthyroidism. J Clin Endocrinol Metab 1997; 82:3633–3636. 13. Kampmann JP, Johansen K, Hansen JEM, Helweg J. Propylthiouracil in human milk: revision of dogma. Lancet 1980; 1:736–738. 14. Tamai H, Mukata T, Matsubayashi S, Fukata S, Komaki G, Kuma K, Kumagai LF, Nagataki S. Treatment of methimazole-induced agranulocytosis using recombinant human granulocyte colony-stimulating factor (rhG-CSF). J Clin Endocrinol Metab 1993; 77:1356–1360. 15. Magner JA, Snyder DK. Methimazole-induced agranulocytosis treated with recombinant human granulocyte colony-stimulating factor (G-CSF). Thyroid 1994; 4:295–296. 16. Balkin MS, Buchholtz M, Ortiz J, Green AJ. Propylthiouracil (PTU)-induced agranulocytosis treated with recombinant human granulocyte colony-stimulating factor (G-CSF). Thyroid 1993; 4:305–309. 17. Fukata S, Kuma K, Sugawara M. Granulocyte colony-stimulating factor (G-CSF) does not improve recovery time from antithyroid drug-induced agranulocytosis: a prospective study. Thyroid 1999; 9:29–31. 18. Solomon DH, Beck JC, Vanderlaan WP, Astwood EB. Prognosis of hyperthyroidism treated by antithyroid drugs. JAMA 1953; 152:201–205. 19. Hershman JM, Givens JR, Cassidy CE, Astwood EB. Long-term outcome of hyperthyroidism treated with antithyroid drugs. J Clin Endocrinol Metab 1966; 26:803–807. 20. Leclere J. Antithyroid drugs a rationale treatment for Graves’ disease? Horm Res 1987; 26: 125–130. 21. Sugrue D, McEvoy M, Feely J, Drury MI. Hyperthyroidism in the land of Graves’: results of treatment by surgery, radioiodine and carbimazole in 837 cases. Q J Med 1980; 49:51– 61. 22. Hedley AJ, Young RE, Jones SJ, Alexander WD, Bewsher PD, and Scottish Automated Follow-up Register Group. Antithyroid drugs in the treatment of Graves’ disease: long-term followup of 434 patients. Clin Endocrinol (Oxf ) 1989; 31:209–218. 23. Weetman AP, McGregor AM, Hall R. Evidence for an effect of antithyroid drugs on the natural history of Graves’ disease. Clin Endocrinol (Oxf ) 1984; 21:163–172. 24. Pimstone B, Joffe B, Pimstone N, Bonnici F, Jackson WPU. Clinical response to longterm propranolol therapy in hyperthyroidism. South Afr Med J 1969; 43:1203–1205. 25. McLarty DG, Brownlie BEW, Alexander WD, Papapetrou PD, Horton P. Remission of thyrotoxicosis during treatment with propranolol. Br Med J 1973; 2:332–334. 26. Mazzaferri EL, Reynolds JC, Young RL, Thomas CN, Parisi AF. Propranolol as primary treatment for thyrotoxicosis. Arch Intern Med 1976; 130:50–56. 27. Codaccioni JL, Orgiazzi J, Blanc P, Pugeat M, Roulier R, Carayon P. Lasting remission in

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45. Wartofsky L, Ransil BJ, Ingbar SH. Inhibition by iodine of the release of thyroxine from the thyroid glands of patients with thyrotoxicosis. J Clin Invest 1970; 49:78–86. 46. Emerson CH, Anderson AJ, Howard WH, Utiger RD. Serum thyroxine and triiodothyronine concentrations during iodide treatment of hyperthyroidism. J Clin Endocrinol Metab 1975; 40:33–36. 47. Shen DC, Wu SY, Chopra IJ, Huang HW, Shian LR, Bian TX, Jeng CY, Solomon DH. Longterm treatment of Graves’ hyperthyroidism with sodium ipodate. J Clin Endocrinol Metab 1985; 61:723–727. 48. Croxson MS, Hall TD, Nicoloff JT. Combination drug therapy for treatment of hyperthyroid Graves’ disease. J Clin Endocrinol Metab 1977; 45:623–631. 49. Sharp B, Reed AW, Tamagna I, Geffner DL, Hershman JM. Treatment of hyperthyroidism with sodium ipodate (Oragraffin) in addition to propylthiouracil and propranolol. J Clin Endocrinol Metab 1981; 53:622–625. 50. Roti E, Robuschi G, Manfredi A, D’Amato L, Gardini E, Salvi M, Montermini M, Barlli AL, Gnudi A, Braverman LE. Comparative effects of sodium ipodate and iodine on serum thyroid hormone concentrations in patients with Graves’ disease. Clin Endocrinol (Oxf ) 1985; 22: 489–496. 51. Costa A. The use of x-ray contrast media in the treatment of hyperthyroidism. J Endocrinol Invest 1979; 2:461–462. 52. Schou MA, Amdisen A, Jensen SE, Olsen T. Occurrence of goitre during lithium treatment. Br Med J 1968; 3:710–713. 53. Lazarus JH, Richards AR, Addison GM, Owen GM. Treatment of thyrotoxicosis with lithium carbonate. Lancet 1974; 2:1160–1162. 54. Byrne AP, Delaney WJ. Regression of thyrotoxic ophthalmopathy following lithium withdrawal. Can J Psychiatry 1993; 38:635–637. 55. Solomon BL, Wartofsky L, Burman KD. Adjunctive cholestyramine therapy for thyrotoxicosis. Clin Endocrinol (Oxf ) 38:39–43. 56. Hagag P, Nissenbaum H, Weiss M. Role of colestipol in the treatment of hyperthyroidism. J Endocrinol Invest 1998; 21:725–731. 57. Lazar L, Kalter-Leibovici O, Pertzelan A, Weintrob N, Josefsberg Z, Phillip M. Thyrotoxicosis in prepubertal children compared with pubertal and postpubertal patients. J Clin Endocrinol Metab 2000; 85:3678–3682. 58. Rivkees SA, Sklar C, Freemark M. The management of Graves’ disease in children, with special emphasis on radioiodine treatment. J Clin Endocrinol Metab 1998; 83:3767–3776. 59. Masiukiewicz US, Burrow GN. Hyperthyroidism in pregnancy: diagnosis and treatment. Thyroid 1999; 9:647–652. 60. Wing DA, Millar LK, Koonings PP, Montoro MN, Mestman JH. A comparison of propylthiouracil versus methimazole in the treatment of hyperthyroidism in pregnancy. Am J Obstet Gynecol 1994; 170:90–95. 61. Davies TF. The thyroid immunology of the postpartum period. Thyroid 1999; 9:675–684. 62. Sabri O, Zimny M, Schreckenberger M, Reinartz P, Ostwald E, Buell U. Radioiodine therapy in Graves’ disease patients with large diffuse goiters treated with or without carbimazole at the time of radioiodine therapy. Thyroid 1999; 9:1181–1188. 63. Tuttle RM, Patience T, Budd S. Treatment with propylthiouracil before radioactive iodine therapy is associated with a higher treatment failure rate than therapy with radioactive iodine alone in Graves’ disease. Thyroid 1995; 5:243–247. 64. Andrade VA, Gross JL, Maia L. Effect of methimazole pretreatment on serum thyroid hormone levels after radioactive treatment in Graves’ hyperthyroidism. J Clin Endocrinol Metab 1999; 84:4012–4016. 65. Perros P. Anti-thyroid drug treatment before radioiodine in patients with Graves’ disease: soother or menace? Clin Endocrinol 2000; 83:1–2. 66. Ross DS, Daniels GH, Stefano PD, Maloof F, Ridgway EC. Use of adjunctive potassium

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iodide after radioactive (131-I) treatment of Graves’ hyperthyroidism. J Clin Endocrinol Metab 1983; 57:250–253. 67. Bartalena L, Marcocci C, Bogazzi F. Relation between therapy for hyperthyroidism and the course of Graves’ ophthalmopathy. N Engl J Med 1998; 338:73–78. 68. Marcocci C, Bruno-Bossio G, Manetti L. The course of Graves’ ophthalmopathy is not influenced by near-total thyroidectomy: a case–control study. Clin Endocrinol (Oxf ) 1999; 51: 503–508.

18 Radioactive Iodide Therapy for Graves’ Disease LESLIE J. DeGROOT University of Chicago/Pritzker School of Medicine, Chicago, Illinois, U.S.A.

I.

OVERVIEW

Radioactive 131 iodide ( 131I) therapy for Graves’ disease was first studied in 1940 and introduced into general practice in 1947. Experience has now accumulated over more than 50 years with treatment of hundreds of thousands of patients. 131 I treatment is currently the most commonly used treatment for hyperthyroidism due to Graves’ disease in adults in the United States and Europe. The expected outcome of treatment is control of hyperthyroidism, and the eventual induction of hypothyroidism in the majority of patients. The treatment also probably exacerbates Graves’ ophthalmopathy in some patients. For the purposes of this discussion, it is assumed that the patient has been correctly diagnosed with hyperthyroidism due to Graves’ disease, is believed to be in need of treatment, and that other conditions causing hyperthyroidism (Table 1) have been excluded. Whether or not to treat subclinical hyperthyroidism remains a question. If the condition (‘‘normal’’ f T4 and f T3 levels and suppressed thyroid-stimulating hormone [TSH]) persists, or if there is evidence of cardiac dysfunction or bone loss, the decision usually would be to treat. II. DECISION FOR USE OF

131

I TREATMENT

The same three treatments—long-term antithyroid drug administration, radioactive iodide (RAI) administration, and surgical resection of most of the thyroid—have been available and in use for the past 50 years. Children and young people up to approximately 18 years are generally treated with antithyroid drugs, if possible, often for several years. If this is unsuccessful, and in the very young, subtotal thyroidectomy is the generally preferred 171

Exogenous thyroid hormone Hydatidiform mole

Tender goiter Nodular goiter Nodular goiter, rarely normal One nodule Variable, with metastasis Small thyroid Goiter

Weeks Prolonged, mild Recent, mild

Prolonged, mild Recent

Recent, mild

Variable

Goiter Small goiter

Physical finding

Familial, prolonged Months

Course of disease

Causes of Thyrotoxicosis

Graves’ disease Transient thyrotoxicosis (painless thyroiditis) Subacute thyroiditis Toxic multinodular goiter Iodide-induced (including amiodarone) Toxic adenoma Thyroid carcinoma

Cause

Table 1

None, NSAID, or steroids

RAIU ⫽ 0, elevated ESR, recent URI, Normal or ↑ Tg Typical scan result

Pregnancy, vaginal bleeding Increased HCG

Zero RAIU; psychiatric illness, low TG

‘‘Hot’’ nodule on scan Functioning metastases

Low RAIU, abnormal scan result

Antithyroids, RAI, surgery Possibly steroids; thyroid ablation between attacks

⫹ Ab, increased RAIU, eye signs Low Ab, no eye signs, RAIU ⫽ 0, Normal or ↑ Tg

Surgery, chemotherapy

Withdrawal, counseling

Surgery, RAI Surgery ⫹ RAI

Antithyroids, time, ablation, withdrawal of iodine source, KClO4

Antithyroids, RAI, surgery

Treatment or comment

Diagnostic finding

172 DeGroot

TSH-R mutation

Congenital or sporadic

Pregnancy, in first trimester

Small gland, no eye signs ↑ FTI, ↓ TSH variable thyrotoxicity Typical thyrotoxicosis

With or without goiter Variable

Variable

Recent, self-limiting

Goiter

Prolonged

Hamburger toxicosis Hyperemesis gravidarum

Goiter

Prolonged

Variable

Goiter Goiter

Recent, mild ?

Thyroid destruction

Choriocarcinoma Excess production of TRH (possibly) TSH-producing adenoma ‘‘Pituitary T3 /T4 resistance’’ Struma ovari

Thyroid ablation

⫹ Family history, germ line mutation

Suppressed TSH and TG, ↓ RAIU

Variable

High HCG, low or absent anti-TPO

Adenomectomy, somatostatin, thyroid ablation Not certain; possibly T3, triac, somatostatin, thyroid ablation Surgery

Excess alpha subunits, ↑ TSH, pituitary adenoma Elevated or normal TSH, no tumor, no α subunit, mild thyrotoxicosis Positive scan result or operation

Reported with 131 I therapy, lymphoma, other causes cited above such as subacute thyroiditis Avoid meat trimmings, including thyroid tissue None, ATD, Abortion

Surgery, chemotherapy Not known

Increased HCG ? Poor response to TRH

RAI Therapy 173

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procedure. Radioactive iodide is withheld by many physicians for patients younger than age 18, except in unusual settings, because of continued fear that it may induce malignant change in the thyroid in some (1). There is, however, a growing tendency to balance this risk against possible adverse effects of surgery, including hypothyroidism, recurrent nerve damage, hypoparathyroidism in 1–10% of children, and the rare fatality (2,3). If antithyroid drug treatment is unsuccessful, this author prefers surgical resection for individuals under age 18, if a well-trained surgeon is available. This concept seems especially important the younger the patient is. If a well-trained surgeon is not available, RAI may carry less risk in individuals 12–18 years of age, and perhaps in this age group the aim should be complete ablation of thyroid tissue. The patient over age 18 with an average case of Graves’ disease is offered therapy with antithyroid drugs or 131 I by most thyroidologists in the United States and Europe (4,5). Exceptions to this may be individuals in whom therapy is urgent, patients who have very large glands, patients in whom RAI uptake is contraindicated by prior administration of iodine, and those who are pregnant or who wish to become pregnant in the immediate future. For these patients, surgery remains an acceptable alternative. Surgery is also favored in individuals with very large goiters, those who have serious ophthalmopathy (at least by some individuals, as discussed below), in the presence of a nodule suspicious for malignancy, and when patients have fear of isotope administration. 131 I treatment is definitely contraindicated in nursing women, during pregnancy, and if RAI uptake (RAIU) is suppressed. Relative contraindications include the presence of a discrete nodule in the thyroid, and moderate to severe ophthalmopathy. Whether to use radioactive iodide in the presence of a nodule is complicated. Clearly one alternative is to do fine needle aspiration (FNA) of the nodule, and consider 131 I treatment if the nodule is benign, or surgery if it is questionable or malignant (6). On the other hand, one may be concerned that radiation to a benign growth in the thyroid, given by the gamma rays administered during 131 I treatment, might lead to malignant change. For this reason, this therapist believes that in the presence of a discrete nodule in the thyroid, surgery is the preferred treatment. Fairly large goiters can be treated by either surgery or radioactive iodide. The cosmetic effect generally will be better with surgery, since huge glands will not shrink to a nonobservable size after 131 I treatment (7).

III. METHOD OF TREATMENT A.

131

I Treatment

Patients with mild-to-moderate hyperthyroidism and moderate-sized goiters (45–60 g) are often treated without antithyroid drug pretreatment. Patients who have coincident heart disease, potential arrhythmias, and large glands, or with severe thyrotoxicosis, are preferably pretreated with antithyroid drugs until they have been rendered euthyroid (8). This approach has the obvious advantage of bringing their thyrotoxicosis under prompt control, and reduces the supply of hormones stored in the gland that might be released after 131 I treatment, leading to a worsening of hyperthyroidism and possible cardiovascular problems (9). While these are rare complications, they can occur. It is unclear whether pretreatment with antithyroid drugs has any effect on potential exacerbation of exophthalmos. If antithyroid drugs are given, they must be stopped by 48 h prior to determination of radioactive iodide uptake or treatment (10). Many studies have evaluated the potential effect of pretreatment with antithyroid drugs on the outcome of therapy, and the results are mixed.

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Some studies indicate that pretreatment lowers the efficacy of 131 I treatment and that fewer patients are rendered euthyroid, while others show no difference (11). Medical therapy before, during, and after 131 I may also include propranolol, 40–160 mg/day, or atenolol, 50–150 mg/day, to reduce tachycardia and ameliorate symptoms of hyperthyroidism. Before treatment, a 24 h radioactive iodide uptake test is performed. This is important for a variety of reasons. First it helps ascertain whether coincident excess iodide administration has not dropped radioactive iodide to a low level. Also, it helps rule out the possibility of so-called painless thyroiditis, the inflammatory thyroid condition that is a variety of hyperthyroiditis occurring independently or in a postpartum state, causing transient release of hormone from the gland and transient thyrotoxicosis associated with low or zero uptake (12). Isotope imaging of the thyroid is generally not required, unless there is a question of a nodule in the thyroid. Even in this case ultrasonography is probably of more value than isotope scintiscanning in planning the treatment. Isotope imaging plays a role in diagnosis of rare cases of thyroid cancer producing thyrotoxicosis, or with ectopic thyroid tissue such as struma ovarii. Apparently 131 I availability, when given in a capsule, is less than when given in solution (13). It has been suggested that uptake and treatment should be done both with capsules, or both with liquid, to avoid errors in treatment. The battle over how to determine the dosage of 131 I has raged for years between those who use some arbitrary fixed dose and others who have proposed specific schemes for treatment based on thyroid weight and 131 I uptake (14–18). The radiation delivered to the thyroid by a dose of 131 I is given by the following equation: Rads ⫽ 63 ⫻ 0.2 ⫻ (microCuries given/volume of gland in ml) ⫻ fractional uptake ⫻ biological half-time. The important variables in this equation are the volume of the gland and the fractional uptake. Variations in these two factors can alter the radiation dose delivered to the gland, by any given amount of 131 I, over a range of 10-fold or greater. Efficacy of 131 I treatment does depend on the radiation dose delivered to the gland, although it is difficult to calculate the exact amount of radiation dose required to control hyperthyroidism. It is almost impossible to determine a dose that will uniformly produce euthyroidism without hypothyroidism. Nevertheless it seems appropriate to base the administered dose on a formula that takes into account uptake at 24 h and apparent size of the gland as determined by palpation or, preferably, ultrasonography. A scale using these factors to provide a useful therapeutic dose is given in Table 2, based on experience over several decades in the Thyroid Clinic at the University of Chicago. However, many therapists simply use a scale of increasing doses based on their estimate of the amount needed, with doses ranging from 5 to 15 or 20 mCi, on some arbitrary base (16,17). The average thyroid in a patient with Graves’ disease weighs approximately 45 g. Based on Table 2, the average dose administered is approximately 9 mCi. The milliCuries given under this program translates to a rad dose to the thyroid of approximately 7400, for the average 9 mCi dose. This radiation dose produces euthyroidism with one administration in 80–90% of patients. A small proportion will require a second dose some months later, and a rare patient will require a third or even fourth dose. This dose is not sufficient to ablate all thyroid tissue routinely, and, as noted, some patients will remain hyperthyroid. Smaller doses will be less effective at prompt induction of euthyroidism. Very large doses are more apt to induce painful thyroiditis or to exacerbate thyrotoxicosis.

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Table 2 Dosage Schedule for

131

I Therapy

Low-dosage protocol Thyroid weight (g)

Desired µCi retained/g thyroid at 24 h

Average dose (rads) assuming 5.9 day thyroid 131 I t1/2

µCi/g

Rads

10–20 21–30 31–40 41–50 51–60 61–70 71–80 81–90 91–100 100⫹

40 45 50 60 70 75 80 85 90 100

3310 3720 4135 4960 5790 6200 6620 7030 7440 8270

80 90 100 120 140 150 160 170 180 200

6200 7440 8270 9920 11580 12400 13240 14060 14880 16540

Moderate-dosage protocol

In contrast to the large radiation dose given to the thyroid, the body dose is roughly a thousandfold lower. The body dose approximates 1 rad/per mCi given and is delivered during both the iodide phase and the phase of distribution of 131 I-labeled hormone produced in the radioactive iodide-treated gland (Table 3). This whole body dose of 5–10 rads is considered insignificant and has never been shown to be associated with induction of genetic defects (18). Medical procedures such as barium enemas can give 1–3 rads, computed tomograms up to 10 rads to the area examined, and the natural background radiation we all receive is approximately 10 rads by age 30. Thus the radiation dose given by radioactive iodide is close to background levels. It is logical to expect that the effects of this radiation would be extremely difficult to discern (Table 3). The possibility of inducing thyroid malignancy has been extensively examined (20). Reports of production of tumors in young children exposed to radioactive iodide, at Chernobyl (1), and in the occasional occurrence of anaplastic carcinoma in patients who have been treated with radioactive iodide, have continued to raise some concern. However, extensive studies conducted in the United States and Europe found that 131 I therapy was not associated with a greater Table 3 Gonadal Radiation Dose (in Rads) from Diagnostic Procedures and

131

I Therapy Males

Females

Procedure

Median

Range

Barium meal Intravenous pyelogram Retrograde pyelogram Barium enema Femur x-ray film 131 I therapy (5 mCi)

0.0300 0.005–0.23 0.43 0.015–2.09 0.58 0.15–2.09 0.3 0.095–1.59 0.92 0.23–1.71 Usually below 1.6

Source: Adapted with permission from J Nucl Med 1976; 17:826.

Median

Range

0.34 0.06–0.83 0.59 0.27–1.16 0.52 0.085–1.4 0.87 0.46–1.75 0.24 0.058–0.68 Usually below 1.6

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incidence of thyroid malignancy than, for example, surgical treatment of the hyperthyroidism (21,22). This may be due to the fact that a high proportion of patients treated with radioactive iodide have no viable thyroid cells left. Very long-term follow-up studies find that radiation is associated with a minute increase in the incidence of gastric, bladder, small bowel, and thyroid cancer, presumably because of the high levels of radiation given to these areas during the treatment (23,24). This risk remains exceedingly low. The course after treatment is usually gradual improvement or stability. Exacerbation of hyperthyroidism can occur in the weeks after 131 I therapy due to damage to the gland and release of preformed hormone, but is exceptional and found primarily when large goiters are treated with high doses of 131 I (7). Hormone levels are generally not increased above pretreatment levels, except in patients who may be rebounding from prior antithyroid drug treatment (25). Over the course of 2–12 weeks, the free thyroxine gradually falls toward normal or below. With 131 I doses such as those described above, approximately 30% of patients will be hypothyroid within 6–12 months. This proportion will increase gradually, so that by 5–10 years, 80 or 90% of patients are hypothyroid and require replacement therapy. However, many of these patients will have some residual thyroid present that may remain active under stimulation by thyroid-stimulating immunoglobulins. Characteristically, the replacement dose of thyroxine required for patients after radioactive iodide treatment is less than that required for complete replacement in patients who, for example, have had total thyroidectomy, reflecting this residual function. Occasionally patients have pain in or swelling of the thyroid during the first weeks after radioactive iodide treatment. This may be due to the beta irradiation and associated gamma ray radiation from 131 I, or to augmented antithyroid immunity. Approximately 90% of the effect of the radiation is due to beta rays, which have a very low range of penetration. Ten percent of the radiation is present as gamma rays, and these certainly can irradiate surrounding structures. Rarely hypoparathyroidism is induced by radiation damage. A high proportion of patients are cured by one treatment, but this is not always the case. Some patients remain toxic and will require antithyroid drug treatment after radioactive iodide therapy. It is preferable to wait for 5–7 days before starting antithyroid drugs, since earlier administration will significantly reduce the effect of radiation to the thyroid. In patients with severe hyperthyroidism, it is conventional to readminister antithyroid drugs approximately 5 days after the isotope is given and to continue the antithyroid drugs until the patient becomes euthyroid. When antithyroid drugs are stopped, or during the untreated course after therapy, it may become apparent that hyperthyroidism has not been cured. Ideally one should wait 3–6 months before giving a second dose of 131 I, to be certain that the full effect of the first dose has been achieved. Sometimes, however, severe hyperthyroidism warrants more prompt retreatment. Although retreatment doubles the radiation administered to the whole body, this remains at a low level, and there is no real objection to administering a second dose, if needed, or even the unusual third dose, for control of hyperthyroidism. Coincident administration of lithium has been used to augment effective radiation to the gland (26). However, this is not a routine procedure. In administering second doses or third doses, it is useful to consider the possibility of ineffective treatment due to rapid 131 I turnover. The biological half-time of the iodide in the thyroid is normally approximately 6 days. In some glands, however, especially those subjected to previous surgery or prior radiation, turnover of the iodide can be accelerated to 1 or 2 days (27). This radically reduces the effect of radiation. It is easy to do a turnover study by measuring uptake at 8, 12, and 48 h after the tracer administration, to make

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certain that turnover is not excessively rapid. If it is found to be accelerated, an appropriate increase in the isotope dose should be given. An alternative to administration of antithyroid drugs for control of hyperthyroidism posttherapy is the administration of potassium iodide, such as two drops of SSKI twice daily, or eight drops of Lugol’s daily (28). This treatment has been used extensively in some clinics. Typically the SSKI is started approximately a week after treatment and brings the patient’s hyperthyroidism down to the normal range. However, potassium iodide administration often induces hypothyroidism in patients previously treated with radioactive iodide. If the iodide is then stopped, the patient may rebound to euthyroidism or even hyperthyroidism. For this reason, it has seemed practical to most therapists to use antithyroid drugs for temporary control if there is no specific contraindication. Another approach to therapy, used in patients in whom it seems important to induce euthyroidism rapidly, is to administer antithyroid drugs beginning 24 h after therapy, and add to two drops of potassium iodide twice daily, beginning with the second dose of the antithyroid drugs (29,30). This combined treatment clearly reduces the radioactive iodide radiation to the thyroid by approximately 30%, but will induce rapid control of hyperthyroidism and is of value in patients with coincident cardiovascular disease. B.

Follow-Up After Treatment

Patients should generally be evaluated at 1 month after treatment and then at 1–2 month intervals until the course has stabilized, with TSH and free T4 levels obtained at each visit. The f T4 provides the most valuable guide to the need for institution of T4 replacement. Supplementation should be started with partial replacement if fT4 approaches low normal, but this may not be needed permanently. TSH may remain suppressed for several months and is thus not always a reliable guide in this period. C.

Radiation Safety

At the practical level, patients who have been given treatment for Graves’ disease can be assured that, by following easy precautions, they will not represent a radiation hazard or harm anyone by casual exposure. The Nuclear Regulatory Commission (NRC) guidelines allow release of patients when the radiation dose to the public will presumably not exceed 0.5 rem in a year, and with written instructions regarding precautions if this dose might exceed 1 rem/year (31). It should always be noted that the isotope can in practice only be passed from person to person by ingestion of bodily secretions such as saliva and urine. The precautions in Table 4 are suggested (31–33).

Table 4 Radiation Precautions 1. 2. 3. 4.

To avoid excess radiation to another person, do not pass bodily secretions to another person, and avoid prolonged exposure within arm’s length (3 ft). Contact with children and pregnant women should be avoided for 3–6 days. Maintain normal hygiene, including washing dishes, not sharing food or beverages, and fully flushing urine. Patients may wish to sleep alone and should avoid close contact over several hours in automobiles and airplanes during the first week after treatment.

RAI Therapy

IV.

179

SPECIAL PROBLEMS

A. Failure to Cure The occasional requirement for multiple 131 I doses administered at intervals of 3–6 months has been described above. If the thyroid can pick up radioactive iodide, there is reason to believe that this therapy can cure hyperthyroidism. However, in some patients, in the presence of large glands and very rapid turnover, the amount of isotope that needs to be administered in some patients becomes very large, and in these patients surgery can be considered. In rare cases surgery is performed after so-called failure of one or two doses of radioactive iodide. There is no special complication associated with surgery after 131 I therapy. B.

Children

The hesitancy to use isotopes in individuals under age 18, and the slow acceptance of its use in children down to age 12, has been described above. C.

Pregnancy

In every female patient of potential child-bearing age, it must be ascertained that she is not pregnant, either by administering the isotope during a known menstrual cycle, or determining by test that pregnancy is not present. If isotope is inadvertently given to a woman who is pregnant, the risk to the fetal thyroid is low prior to the twelfth week of fetal life. After this, because the thyroid is accumulating iodide, destruction of the fetal thyroid can occur. On the other hand, fear of adverse effects of radiation to the developing fetus, or the induction of later malignancy, are serious considerations, so isotope administration any time during pregnancy must be avoided. D. Nursing Women Large amounts of iodide will be transferred into breast milk and can have serious adverse effects on the infant’s thyroid. Isotope therapy must be postponed until after weaning. E.

Relation to Conception

It is not possible to prove that there is any increased risk of having an infant with a congenital abnormality caused by a parent’s recent exposure to 131 I therapy. However, patients are generally advised to wait 4–6 months after 131 I therapy before attempting to conceive. Possibly this allows any radiation damage to DNA to be repaired. F. Antithyroid Drugs As indicated above, many patients can be treated directly without antithyroid drug. If pretreatment these agents are given, it is usual to stop administration for 48 h prior to 131 I uptake or treatment. However, it has been shown that antithyroid drug administration is often associated with only partial inhibition of iodide binding and, in some clinics, patients are treated while taking antithyroid drugs (34). Although this approach is possible in the hands of those who have carefully analyzed and adapted their procedure, because of the logical possibility of reducing the effectiveness of isotope treatment, this method is generally to be avoided.

180

G.

DeGroot

Thyrotoxicosis After Treatment

Exacerbation of hyperthyroidism can occur in patients with very large glands and receiving high treatment doses, and can induce congestive heart failure (CHF), angina, or, more commonly, arrhythmias. Treatment is by addition of antithyroid drugs (especially propylthiouracil to inhibit T4 → T3 conversion), with or without use of potassium iodide, along with specific therapy for associated problems such as CHF or arrhythmias.

V.

OPHTHALMOPATHY

The relationship of 131 I therapy to exacerbation of ophthalmopathy remains important, and controversial. The ophthalmopathy associated with Graves’ disease generally begins during the development of hyperthyroidism and regresses gradually after therapy. Mild ophthalmopathy may be present in most patients, but in approximately 25% of patients the eye signs are clinically significant. In a small fraction (perhaps 5%) the ocular problem is severe (35). Smoking is known to be associated with a higher incidence and progression of ophthalmopathy. Careful studies by Tallstedt et al. (36,37) showed that radioactive iodide administration was more likely to be associated with progression or exacerbation of ophthalmopathy than was antithyroid drug treatment or surgery. Although these findings have been contested (38), there is also corroborating evidence (39–43). A corollary of this study is that radioactive iodide treatment should be carefully considered in patients with significant ophthalmopathy. A study by Bartalena et al. has shown that administration of prednisone (0.5 mg/kg bw for 30–60 days), beginning at the time of RAI administration, can reduce the incidence of exacerbation of ophthalmopathy, compared to the administration of radioactive iodide alone (44). Current evidence suggests that ophthalmopathy is initiated by immune responses initially directed to the TSH receptor (TSHR) present in the thyroid. T cells and possibly antibodies carrying out the process in the orbits are attacking cells such as orbital preadipocytes and muscle cells that bear the TSHR protein (45). Destruction of the thyroid by radiation can release antigens and augments antithyroid peroxidase (TPO), antithyroglobin (TG), and TSHR antibody levels (46), augments T-cell reactivity to TSHR (47), and thus may logically exacerbate ophthalmopathy. Reduction in antigenic load by removal of the thyroid could be expected to reduce the immune response gradually, although this would not remove the putative antigen from the orbit, or reduce the secondary immunity to orbital antigens that can develop during the course of the ophthalmopathy. There is no unanimity in how to apply such concepts to practice, but the following can be suggested for guidelines. In patients with no significant clinical ophthalmopathy, radioactive iodide can be given and ophthalmopathy, should it develop, can be treated by corticosteroids or radiation. In patients who present with moderate ophthalmopathy, such as Hertel readings ⬎20 mm, significant inflammation of the muscles, or periorbital edema, but without more serious signs, it is appropriate to administer prednisone at the time of radioactive iodide treatment and for at least 1 month, with tapering of the dose after that time (44). However, this author believes that patients with severe ophthalmopathy (Hertel readings ⬎23 or 24 mm, diplopia, severe periorbital edema, and especially if signs are progressing) are best treated by preparation with antithyroid drugs, thyroidectomy, and radioactive iodide ablation of residual thyroid tissue (with prednisone coverage) (39,40). Although this approach cannot certify that the autoimmune process exacerbating ophthalmopathy will be avoided, it does offer the theoretical foundation for curing the hyperthy-

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181

roidism and removing exposure to antigens from the thyroid. In our experience it has been successful in ameliorating ophthalmopathy. VI.

COURSE AFTER TREATMENT

After radioactive iodide administration, it is typical for antithyroid antibodies to become more elevated and for thyroid-stimulating immunoglobulin levels to be augmented for 6– 12 months, probably due to release of antigen from the thyroid. This process tends to subside along with the onset of hypothyroidism in most patients during the second year after treatment. The long-term effects associated with radioactive iodide administration have been studied. There is some decrease in longevity due to cardiac problems, bone fractures, and other problems (48). However, these effects appear to be intrinsic to the hyperthyroidism rather than an effect of the radioactive iodide treatment. The very small risk of radiation-induced bladder or stomach cancer has been described above (23,24). VII.

DIALYSIS

Patients on dialysis can be treated with 131 I. Typically iodide levels in blood are elevated in such patients, and isotope retention is prolonged (49). The conventional dose calculation described above can be used but, for safety’s sake, it is probably best to reduce administered doses by 50–80% of standard calculations. All disposable dialysis equipment must be treated as being contaminated with radioactive iodide. Fluids can be disposed of in ordinary sewage, as can patients’ urine or feces. VIII. SPECIAL ASPECTS OF RADIOACTIVE IODIDE TREATMENT Occasionally patients remain resistant to radioactive iodide treatment and the possibility of surgical resection appears, as described above. There is no contraindication to surgery after radioactive iodide treatment. Patients with so-called painless thyroiditis or transient thyrotoxicosis cannot be treated at the time they are hyperthyroid, because the RAI uptake is low or zero. Occasionally such patients have multiple recurrences of the problem. Radioactive iodide has been administered in the interim after an episode when RAIU is normal, to ablate the gland and prevent recurrence. The use of radioactive iodide to ablate the thyroid in patients who have progressive ophthalmopathy after RAI therapy is also possible. This concept has been described above. After radioactive iodide treatment, some patients experience exacerbation of ophthalmopathy. Such patients may be intrinsically hypothyroid and receiving replacement therapy, but often they will be found to have a functioning thyroid gland, as measured by radioactive iodide uptake, which is under continued stimulation by TSI, even though they are unable to maintain euthyroidism without supplementation. It is logical to assume that the presence of the thyroid tissue stimulated by TSI, releasing antigenic material into the bloodstream, can be related to continuing and worsening ophthalmopathy. This author believes it is appropriate to ablate such residual tissue by radioactive iodide treatment, and we have done so in a large series of patients with generally beneficial results. The dose of radioactive iodide given is chosen to ablate residual tissue; usually 20–30 mCi are administered. If uptake is significant, in the range of 5–15%, it is appropriate to administer prednisone as described above during the administration and in the 2–3 months posttreat-

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ment, to prevent possible exacerbation of ophthalmopathy by 131 I-induced release of antigens from the thyroid. This prophylaxis does not guarantee that exacerbation will not occur, but has been shown to be useful and beneficial (39). The effects of such treatment are usually seen gradually over the subsequent 3–12 months. A careful prospective randomized study is needed to prove whether such therapy is beneficial. However, it is certain that destruction of such thyroid tissue has no adverse effect (other than possible exacerbation of the ophthalmopathy), since the most that it can induce is a slight increase in the dosage of thyroxine required for replacement. The whole-body radiation associated with this is considered unimportant. Thyroid ablation as treatment for progressive ophthalmopathy can be done along with any other therapy that may be required, such as the use of steroids, radiation, or even, in rare cases, decompression. ACKNOWLEDGMENTS This work was supported by National Institutes of Health Grant No. 2-RO1-DK27384, the Knoll Pharmaceutical Company, and the David Wiener Research Fund. REFERENCES 1. Pacini F, Vorontsova T, Demidchik E, Molinaro E, Agate L, Romei C, Shavrova E, Cherstvoy E, Ivashkevitch Y, Kuchinskaya E, Schlumberger M, Rouga G, Felesi M, Pinchera A. PostChernobyl thyroid carcinoma in Belarus children and adolescents: comparison with naturally occurring thyroid carcinoma in Italy and France. J Clin Endocrinol Metab 1997; 82:3563– 3569. 2. Rivkees SA, Sklar C, Freemark M. The management of Graves’ disease in children, with special emphasis on radioiodine treatment. J Clin Endocrinol Metab 1998; 83:3767–3776. 3. Hamburger JI. Management of hyperthyroidism in children and adolescents. J Clin Endocrinol Metab 1985; 60:1019–1024. 4. Leech NJ, Dayan CM. Controversies in the management of Graves’ disease. Clin Endocrinol 1998; 49:273–280. 5. Wartofsky L, Glinoer D, Solomon B, Nagataki S, LaGasse R, Nagayama Y, Izumi M. Differences and similarities in the diagnosis and treatment of Graves’ disease in Europe, Japan, and the United States. Thyroid 1991; 1:129–135. 6. Cantalamessa L, Baldini M, Orsatti A, Meroni L, Amodei V, Castagnone D. Thyroid nodules in Graves’ disease and the risk of thyroid carcinoma. Arch Intern Med 1999; 159:1705–1708. 7. Sabri O, Zimny M, Schreckenberger M, Reinartz P, Ostwald E, Buell U. Radioiodine therapy in Graves’ disease patients with large diffuse goiters treated with or without carbimazole at the time of radioiodine therapy. Thyroid 1999; 9:1181–1188. 8. Kaplan MM, Meier DA, Dworkin HJ. Treatment of hyperthyroidism with radioactive iodine. Endocrinol Metab Clin North Am 1998; 27:205–221. 9. Stensvold AD, Jorde R, Sundsfjord J. Late and transient increases in free T4 after radioiodine treatment for Graves’ disease. J Endocrinol Invest 1997; 20:580–584. 10. Cooper DS, Bode HH, Nath B, Saxe V, Maloof F, Ridgway EC. Methimazole pharmacology in man: studies using a newly developed radioimmunoassay for methimazole. J Clin Endocrinol Metab 1984; 58:473–479. 11. Marcocci C, Gianchecchi D, Masini I, Golia F, Ceccarelli C, Bracci E, Fenzi GF, Pincher A. A reappraisal of the role of methimazole and other factors on the efficacy and outcome of radioiodine therapy of Graves’ hyperthyroidism. J Endocrinol Invest 1990; 13:513–520. 12. Ginsberg J, Walfish PG. Post-partum transient thyrotoxicosis with painless thyroiditis. Lancet 1977; 1:1125–1128.

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33. 34.

35. 36. 37.

38.

39. 40.

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44.

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46. 47.

48. 49.

DeGroot from adult patients receiving 131 I therapy for thyrotoxicosis. Nucl Med Commun 1993; 14: 160–168. Grigsby PW, Siegel BA, Baker S, Eichling JO. Radiation exposure from outpatient radioactive iodine (131 I) therapy for thyroid carcinoma. JAMA 2000; 283:2272–2274. Sabri O, Zimny M, Schulz G, Schreckenberger M, Reinartz P, Willmes K, Buell U. Success rate of radioiodine therapy in Graves’ disease: the influence of thyrostatic medication. J Clin Endocrinol Metab 1999; 84:1229–1233. Sridama V, DeGroot LJ. Treatment of Graves’ disease and the course of ophthalmopathy. Am J Med 1989; 87:70–73. Tallstedt L, Lundell G, Torring O, Wallin G, Ljunggren JG, Blomgren H, Taube A. Occurrence of ophthalmopathy after treatment for Graves’ disease. N Engl J Med 1992; 326:1733–1738. Torring O, Tallstedt L, Wallin G, Lundell G, Ljunggren J-G, Taube A, Saaf M, Hamberger B, Thyroid Study Group. Graves’ hyperthyroidism: treatment with antithyroid drugs, surgery, or radioiodine—a prospective, randomized study. J Clin Endocrinol Metab 1996; 81:2986– 2993. Manso PG, Furlanetto RP, Wolosker AMB, Paiva ER, de Abreu MT, Maciel RMB. Prospective and controlled study of ophthalmopathy after radioiodine therapy for Graves’ hyperthyroidism. Thyroid 1998; 8:49–52. DeGroot LJ, Benjasuratwong Y. Evaluation of thyroid ablative therapy for ophthalmopathy of Graves’ disease. Orbit 1996; 15:187–196. DeGroot LJ, Gorman CA, Pinchera A, Bartalena L, Marcocci C, Wiersinga WM, Prummel MF, Wartofsky L. Radiation and Graves’ ophthalmopathy. J Clin Endocrinol Metab 1995; 80:339–349. De Bellis A, Bizzaro A, Perrino S, Coronclla C, Iorio S, Pepe M, Guaglione M, Wall JR, Bellastella A. Improvement of severe ophthalmopathy and decrease of antibodies against extraocular muscles, G2s, and Fp subunit of succinate dehydrogenase after near-total thyroidectomy in Graves’ disease. J Endocrinol Invest 2000; 23:14. Moleti M, Mattina F, Lo Presti VP, Baldari CS, Bonanno N, Trimarchi F, Vermiglio F. Role of residual thyroid tissue ablation after thyroidectomy for Graves’ disease: its effects on the course of related ophthalmopathy. J Endocrinol Invest 2000; 23:37. Fernandez Sanchez JR, Rosell Pradas J, Carazo Martinez O, Torres Vela E, Escobar Jimenez F, Garbin Fuentes I, Vara Thorbeck R. Graves’ ophthalmopathy after subtotal thyroidectomy and radioiodine therapy. Br J Surg 1993; 80:1134–1136. Bartalena L, Marcocci C, Bogazzi F, Manetti L, Tanda ML, Dell’Unto E, Bruno-Bossio G, Nardi M, Bartolomei MP, Lepri A, Rossi G, Martino E, Pinchera A. Relation between therapy for hyperthyroidism and the course of Graves’ ophthalmopathy. N Engl J Med 1998; 338:73– 78. Bahn RS, Dutton CM, Natt N, Joba W, Spitzweg C, Heufelder AE. Thyrotropin receptor expression in Graves’ orbital adipose/connective tissues: potential autoantigen in Graves’ ophthalmopathy. J Clin Endocrinol Metab 1998; 83:998–1002. Fenzi G, Hashizume K, Roudebush CP, DeGroot LJ. Changes in thyroid-stimulating immunoglobulins during antithyroid therapy. J Clin Endocrinol Metab 1979; 48:572–576. Soliman M, Kaplan EL, Abdel-Latif A, Scherberg N, DeGroot LJ. Does thyroidectomy, RAI therapy, or antithyroid drug treatment alter reactivity of patients’ T cells to epitopes of thyrotropin receptor in autoimmune thyroid diseases? J Clin Endocrinol Metab 1995; 80:2312–2321. Franklyn JA, Maisonneuve P, Sheppard MC, Betteridge J, Boyle P. Mortality after the treatment of hyperthyroidism with radioactive iodine. N Engl J Med 1998; 338:712–718. Kaptein EM, Levenson H, Siegel ME, Gadallah M, Akmal M. Radioiodine dosimetry in patients with end-stage renal disease receiving continuous ambulatory peritoneal dialysis therapy. J Clin Endocrinol Metab 2000; 85:3058–3064.

19 Thyroidectomy for Graves’ Hyperthyroidism JIN-WOO PARK and ORLO H. CLARK University of California, San Francisco, and Mount Zion Medical Center, San Francisco, California, U.S.A.

I.

INTRODUCTION

Graves’ disease is the most common cause of hyperthyroidism. The hyperthyroidism associated with Graves’ disease is caused by autoantibodies (TSAb) against thyroidstimulating hormone (TSH) receptors that stimulate thyroid cells. The exact mechanism of recognition of autoantigens and production of autoantibodies is, however, not known. The cause of Graves’ disease is generally thought to be multifactorial based on both genetic susceptibility and environmental factors (Table 1). In most patients the diagnosis of Graves’ disease is suspected based on diffuse thyroid enlargement, eye signs (ophthalmopathy), with characteristic clinical manifestations of hyperthyroidism. When the clinical manifestations are mild, early, or atypical, laboratory confirmation of hyperthyroidism (elevated serum thyroid hormone levels and decreased TSH) and presence of autoantibodies (thyroid peroxidase–microsomal antigen, antithyroglobulin, or TSH receptor antibody) are helpful to differentiate Graves’ disease from other causes of hyperthyroidism (1). Treatment options differ according to the causes of hyperthyroidism. It is therefore most important to diagnose accurately the cause of the disease (Table 2). Graves’ disease can be differentiated from other causes of hyperthyroidism by the presence of a family history, bilateral diffuse thyroid enlargement, an increased radioactive iodine uptake (RAIU), eye signs, and the presence of high antithyroid antibody titers. Currently three effective treatment modalities are available for treating the overactive thyroid gland in patients with Graves’ disease: antithyroid drug treatment, radioiodine therapy, and surgery (thyroidectomy). Antithyroid medication results in inhibition of thyroid hormone synthesis. Ablative treatment with radioiodine therapy or surgical resection results in reduction 185

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Table 1 Causative Factors in Graves’ Disease Genetic factors

Environmental factors

HLA; HLA-DRB3 (89,90), HLA-DQB (91,92) IFN-γ microsatellite polymorphism (93) CTLA-4 (94) GD-1, GD-2, and GD-3 genes (95) 18q21 locus (96)

Iodine intake (2,3) Smoking (4) Stressful life event (5,6) Infectious agents; retrovirus (7) Yersinia enterocolitica. (8,9)

in thyroid gland mass and secretion of thyroid hormone. There is no exclusive treatment for all patients with Graves’ disease because each treatment has its own advantages and disadvantages. Thyroidectomy was the first successful treatment for patients with Graves’ disease. The results of thyroid surgery have improved because of advances in perioperative treatments and modern operative technique. When performed by an experienced surgeon, thyroidectomy is the most reliable treatment for inducing the euthyroid state rapidly and maintaining it for a long time without significant complications. II. PREOPERATIVE PREPARATION Prior to surgery, all patients should be rendered euthyroid to prevent thyroid storm during or immediately after surgery. Thionamide antithyroid drugs, beta-blockers, and iodine have been used to control hyperthyroidism for a short time before operation. Thionamide drugs such as propylthiouracil (PTU) and methimazole inhibit thyroid hormone synthesis. It usually requires a high oral loading dosage (PTU 100–300 mg four times daily or methimazole 10–30 mg three times daily) at first. The dosage can be reduced to a maintenance level (PTU 100–300 mg daily or methimazole 10 mg daily) in about 6 weeks when the patient becomes euthyroid. Propranolol, a beta-blocker, controls the peripheral manifestations of hyperthyroidism in various dosages (40–480 mg/day, orally). Preparing patients with beta-blockers can relieve the clinical manifestations of hyperthyroidism rapidly but the patients remain Table 2 Differential Diagnosis of Hyperthyroidism According to Its Cause Increased thyroid hormone secretion

Increased thyroid hormone release

Increased thyroid or thyroid hormone intake

Other disorders

Graves’ disease Toxic multinodular goiter Toxic adenoma Jod-Basedow hyperthyroidism Metastatic functioning thyroid cancer TSH secreting pituitary tumors (rare) Subacute thyroiditis Hashimoto’s thyroiditis Infiltration of the thyroid with tumors or infection Factitious and medicamentosa Intake of desiccated thyroid Intake of raw or undercooked thyroid Choriocarcinoma Hydatidiform mole Struma ovarii

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biochemically hyperthyroid (10). Additional medications are therefore required to control the hyperthyroidism. Short-term use of iodine induces inhibition of thyroid hormone release (11). Iodine also decreases the vascularity of the thyroid gland (12). A saturated solution of potassium iodide (SSKI; 3 drops three times daily) or a Lugol’s solution (iodine and potassium iodide, 3 drops two times daily) should be administered for a least 1 week before thyroidectomy. Thionamide drugs and iodine are discontinued on the day of surgery, but propranolol should be tapered over 3 or 4 days after thyroidectomy because of the long half-life of thyroid hormone. Antithyroid drugs and beta-blockers are commonly used together because they relieve symptoms and return the patient to a euthyroid state (10,13). The most common regimen is a combination of thionamide drugs with beta-blockers and institution of iodine 10 days prior to surgery. For patients who are allergic to antithyroid drugs and betablockers, sodium ipodate (14), lithium carbonate (15), glucocorticoid therapy (16), and plasmapheresis (17) can be used to prepare for surgery.

III. SURGICAL OPTIONS: THYROIDECTOMY Thyroidectomy removes most or all of the diseased gland, depending upon the extent of surgery, and therefore immediately reduces thyroid hormone secretion. It also appears to reduce the autoimmune reaction in some patients. Although bilateral subtotal thyroidectomy or a total lobectomy on one side and a subtotal on the other have been recommended as a first choice in surgical treatment for Graves’ disease, the ideal size of the thyroid remnant is still debated. The smaller the remnant, the lower the risk of recurrent or persistent hyperthyroidism but the higher risk of postoperative hypothyroidism (18,19). Most experienced surgeons recommend leaving a 4–7 g remnant. When less than 4 g thyroid tissue is left, the risk of hypothyroidism is relatively high (about 40%). When more than 7 g thyroid tissue is left, the recurrence rate of hyperthyroidism is relatively high (about 15%). When the size of thyroid remnant is compared as a contributing factor to surgical result, the method of its measurement and vascular supply must be considered. At operation, a portion of the resected thyroid gland weighing 5 g can be precisely weighed so that the desired size of the remnant can be accurately determined. Branches of the inferior thyroid artery supplying the remnant should be preserved. There are two methods of leaving remnant thyroid tissue after thyroidectomy: small remnants of 2–3 g bilaterally or a single 4–5 g remnant on one side. Bilateral remnants can potentially increase the morbidity associated with injuries of recurrent laryngeal nerves or parathyroid glands. We prefer to leave tissue only on one side or to use the Hartley-Dunhill operation. Although subtotal thyroidectomy cannot reliably avoid recurrent hyperthyroidism, near-total and total thyroidectomy are effective and safe. Nowadays near-total (18,20) or total thyroidectomy (21–23) is increasingly recommended by many, but certainly not all, to treat benign thyroid conditions. Proponents of total thyroidectomy in the treatment of Graves’ disease suggest that it avoids the worsening of thyroid humoral autoimmunity and the relapse of hyperthyroidism without increasing the complication rate compared with subtotal thyroidectomy (23–25). Total thyroidectomy appears to improve Graves’ ophthalmopathy in some but certainly not all patients (24). A disadvantage of total thyroidectomy is that it results in expected hypothyroidism and patients require life-long hormonal replacement.

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The extent of thyroidectomy should be based on its specific risks and benefits. The authors recommend the Hartley-Dunhill operation (total lobectomy on one side and subtotal lobectomy on the other side, leaving 4–5 g thyroid tissue) for most patients and total thyroidectomy for patients with Graves’ ophthalmopathy or nodules suspicious for cancer (26). IV.

POSTOPERATIVE THYROID FUNCTION

Either subtotal or total thyroidectomy by meta-analysis is more than 90% successful in treating patients with Graves’ disease (27). No cases of recurrent hyperthyroidism occurred after total thyroidectomy. Subtotal thyroidectomy induced a euthyroid state in almost 60% of patients, with an 8% rate of persistent or recurrent hyperthyroidism (27). When the aim of surgery in Graves’ disease is to avoid recurrent hyperthyroidism, total thyroidectomy is an ideal choice when it can be done safely. Total thyroidectomy, however, results in hypothyroidism. When one wishes to maintain normal thyroid function, an adequate amount of the thyroid gland should be preserved by subtotal thyroidectomy. Although a total thyroid remnant of about 5 g can maintain the euthyroid state, preserving thyroid tissue increases the risk of recurrent hyperthyroidism. Thyroid remnant size is the key predictor of postoperative thyroid function (28). The activity of the remnant, however, cannot always be predicted. Remnant size does correlate with recurrent hyperthyroidism (larger remnant) or postoperative hypothyroidism (small, less than 4 g, or no remnant) (18,29,30). Young patients (especially under 20 years) are at higher risk of recurrent hyperthyroidism (31,32). Therefore a small remnant should be left. Other factors, although weak, that increase the risk of recurrent hyperthyroidism include antimicrosomal hemagglutination antibodies (MCHA) (32), elevated TSH-binding inhibition immunoglobulins (TBII) or TSH receptor antibodies before or after operation (29,30,33,34), pre-existing ophthalmopathy (34), and lymphocytic infiltration of the remnant (35). Vascular impairment or fibrosis of the remnant, in contrast, increases the risk of hypothyroidism. V.

POSTOPERATIVE COMPLICATIONS

Surgical complications include bleeding, infection, and hoarseness due to injury to the recurrent laryngeal nerve injury or external laryngeal nerve injury, as well as hypoparathyroidism, keloid, or seroma formation. Postoperative bleeding can be prevented by meticulous hemostasis. Thyroidectomy is somewhat more difficult in patients with Graves’ disease than in patients with nodular goiter because of the increased vascularity. It is therefore not surprising that complications are more common, especially after total thyroidectomy (36). Advances in thyroid surgery during the last several decades have reduced the frequency of serious complications such as hypoparathyroidism and recurrent laryngeal nerve paralysis with rates now lower than 1% (27,37). The incidence of complications after total or near-total thyroidectomy is now reported to be comparable to that of subtotal thyroidectomy (18,23,27). VI.

POSTOPERATIVE FOLLOW-UP

Total or near-total thyroidectomy obviously results in hypothyroidism. Patients must therefore receive life-long replacement therapy with thyroxine. In surgically induced hypothy-

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roidism, a positive correlation has been reported to exist between the TSH level and TSAb and TPO autoantibody levels. Replacement with thyroid hormone should be instituted within several days following thyroidectomy in patients with total or near total thyroidectomy. This will eliminate transient hypothyroidism and stimulation of autoantibody levels (18,38). Subtotal thyroidectomy stimulates autoantibody production less than treatment with radioiodine. Most patients are euthyroid after subtotal thyroidectomy that leaves 4–7 g of thyroid tissue. Unfortunately it does not always result in a permanent euthyroid condition (39). Some patients subsequently experience hypothyroidism, with an incidence of less than 1% per year in contrast to the 3% per year after 131I treatment. Overall, 20– 30% of patients experience hypothyroidism (31,40,41) and 7–15% experience recurrent hyperthyroidism, depending on the size of the remnant (27,41). Long-term follow-up with blood TSH level obtained each year is therefore necessary. VII.

SPECIAL CONSIDERATIONS

A. Graves’ Disease Associated with Pregnancy Graves’ disease is the most common cause of thyrotoxicosis in pregnant women. During pregnancy, a euthyroid state is maintained but there are complex changes in thyroid physiology. Pregnancy elevates total serum T4 by an increase in maternal T4 secretion by human chorionic gonadotropin (HCG) and an increase in thyroxine-binding globulin (TBG) (42). Diagnosing Graves’ disease during pregnancy may be difficult or delayed because both conditions may have similar clinical manifestations, and because pregnancy induces physiological changes in thyroid function. Characteristic clinical features such as diffuse thyroid enlargement, eye signs, and a suppressed TSH level with an elevated T3 or free T4 level help to confirm the diagnosis. The treatment of hyperthyroidism associated with pregnancy may be challenging because both the fetus and mother must be considered. The mainstay of treatment is antithyroid medication. When antithyroid drugs fail to restore the euthyroid state or high levels of medications are required, surgical treatment is a safe and effective alternative therapy during the second semester (43,44). Radioiodine ablation is obviously contraindicated because of its transplacental passage to fetus with destruction of the fetal thyroid gland. The fetal or neonatal thyroid gland can be stimulated by transplacental passage of maternal thyroid stimulating antibodies in patients with Graves’ disease (45). As a result, fetal and neonatal hyperthyroidism can be induced. Fetal hyperthyroidism may be associated with intrauterine growth retardation, and even intrauterine death. Treatment of fetal hyperthyroidism includes administration of antithyroid drugs to the mother with careful fetal monitoring (46). Hyperthyroid neonates should be treated with antithyroid drugs, beta-blockers, and iodine. Nonremitting causes of neonatal hyperthyroidism rarely require surgical treatment (46). B.

Children

Optimal treatment for thyrotoxicosis remains controversial in adults, but more so in children because of additional factors such as growth and development and the potential longterm effects of radioiodine. Most children with Graves’ disease are initially treated with antithyroid drugs combined with a beta-adrenergic blocking agent to control symptoms rapidly. Although antithyroid drugs can induce long-term remission in 40–60% of patients

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(those with small goiters responding best), some children have disease refractory to this treatment (47–49). Although high thyroidal radioactive iodine uptake, the presence of TSH-binding-inhibiting antiglobulin (TBII) or TSAb, and elevated serum thyroglobulin levels can help predict relapse of hypothyroidism. Negative studies are far from precise in predicting permanent remission (50). The main reasons for failure of treatment with antithyroid drugs are side effects and noncompliance. Children who fail to respond to antithyroid drug therapy can be treated with surgery or radioiodine therapy. We prefer to avoid radioiodine therapy except in medical centers with protocols to evaluate such children prospectively, because thyroid cancer and primary hyperparathyroidism have been reported in children with Graves’ disease treated with radioiodine (51,52). Although radioiodine therapy induces long-term remission from hyperthyroidism in about 90% of patients within several months, virtually all successfully treated children eventually experience hypothyroidism (53,54). Because of a high rate of relapse following medical therapy, and because of the reluctance to use radioiodine therapy in children, thyroidectomy is usually recommended. The extent of thyroidectomy in children is controversial. Because recurrent hyperthyroidism is more common in children most authorities recommend either leaving less than 2– 3 g thyroid tissue, or performing a total or near-total thyroidectomy (26,55,56). Surgical treatment provides a safe, rapid, and cost-effective treatment with a high success rate in childhood Graves’ disease. Careful follow-up with yearly blood TSH testing after operation is essential to detect hypothyroidism. C.

Ophthalmopathy

Graves’ ophthalmopathy is a serious extrathyroidal manifestation of Graves’ disease that can impair the quality of life of affected patients. Ophthalmopathy is considered to be at least as troublesome as the systemic thyroid problems in about one-third of patients (57). Despite recent advances in the understanding of its pathogenesis, treatment of these ophthalmic manifestations remains difficult (58). Prevention or correction of both hyper- and hypothyroidism is essential because ophthalmopathy can be aggravated by either of these conditions. Most recent studies suggest that radioiodine therapy has a higher risk for aggravating Graves’ ophthalmopathy than does thyroidectomy (59–61). This might be due to the relatively longer exposure to a noneuthyroid state during radioiodine therapy than for other treatments and because thyroid-stimulating antibody levels are higher after radioiodine therapy. Several predisposing factors for exacerbation of Graves’ ophthalmopathy after radioiodine treatment have been reported, including preexisting active ophthalmopathy, smoking, high pretreatment T3 levels, and high posttreatment TSH levels (62,63). Surgical treatment can also aggravate Graves’ ophthalmopathy immediately after operation, and one should always wait until the eyes have stabilized before performing thyroidectomy. Thyroidectomy is contraindicated in patients with rapidly progressive ophthalmopathy unless steroids are used during the perioperative period. Despite the above comments several reports have documented that surgical treatment for patients with changing ophthalmopathy, regardless of its extent of thyroidectomy, is not associated with postoperative aggravation of ophthalmopathy (20,24,33,64). Some authors, including our group, recommend total thyroidectomy for patients who have Graves’ ophthalmopathy (26,34). Thyroid ablation by total thyroidectomy rather than subtotal thyroidectomy can theoretically improve the ophthalmopathy by decreasing the autoimmune reaction directed

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against antigens shared by the thyroid and the orbit. In some patients, Graves’ ophthalmopathy dramatically regresses after total thyroidectomy, but the results are unpredictable. D. Cancers Associated with Graves’ Disease Controversy remains concerning whether patients with Graves’ disease are more likely to have or to develop thyroid cancers. It is also uncertain whether radioiodine therapy is more likely to result in benign and malignant thyroid tumors than is subtotal thyroidectomy in these patients. According to the Collaborative Thyrotoxicosis Study Group (CTSG), long-term risk of developing benign thyroid nodules was more likely after ablative therapy with radioiodine therapy, but thyroid cancers did not seem to occur more frequently (65). More recent reports, however, suggest a very low but significant risk of thyroid cancer occurring after radioiodine therapy for Graves’ disease (66,67). There also appears to be an increased risk of premature death in patients with Graves’ disease who are treated with radioiodine (51). Thyroid cancer has been documented in 2.6–6.4% of surgically treated patients (68–73). In those patients with thyroid nodules, the incidence of thyroid carcinoma is 10–21.4% (69,70,74). Some authors recommend total thyroidectomy for all patients with Graves’ disease and a thyroid nodule (69,70). However thyroid nodules in Graves’ disease are common (70,74), and the majority of these are benign. Although the preoperative diagnosis of thyroid carcinoma associated with Graves’ disease is usually difficult because of masking by the diffusely enlarged goiter and the typically low index of suspicion, a thyroid scan and fine needle aspiration cytology (FNAC) are helpful for evaluating nodules in Graves’ glands (74,75). Papillary thyroid carcinoma is the most frequent thyroid cancer in Graves’ goiter; follicular carcinomas are infrequent (25,68,69,71). The behavior of thyroid carcinomas associated with Graves’ disease is of interest and several investigators have reported that thyroid carcinomas in this setting are more aggressive. They suggest that the cancers are stimulated by thyroid-stimulating antibodies and have suggested total ablation for these patients (68,71,76,77). Other investigators have failed to show significant differences in prognosis or tumor behavior in these patients (78,79). Although TSAb may play a role in tumor behavior in patients with Graves’ disease, a delay in diagnosis may also contribute to a more advanced thyroid cancer at diagnosis in some patients. Therefore, conventional treatments for differentiated thyroid carcinomas can be used in patients with thyroid carcinomas associated with Graves’ disease and thyroid nodules, but at least a total lobectomy should be done on the side of a nodule that could be cancer. Immunosuppressive therapy should be considered for patients with recurrent or persistent thyroid cancer whose disease fails to respond to total or near-total thyroidectomy, radioiodine ablation, and TSH-suppressive therapy (26). E.

Treatment for Recurrent Hyperthyroidism After Thyroidectomy

Recurrent hyperthyroidism after thyroidectomy can be treated surgically or with another dose of 131I. For most patients with recurrent hyperthyroidism after subtotal thyroidectomy, radioiodine therapy is usually recommended. Overt recurrent hyperthyroidism is often relatively refractory to antithyroid drug therapy, but in latent hyperthyroidism remission can be achieved spontaneously in some patients (80). Although surgery is generally not considered for the treatment of relapses after subtotal thyroidectomy, reoperation can be safe and effective when done by an experienced surgeon (81). When the Hartley-Dunhil operation is used as the initial surgical option, that is removing all thyroid tissue on one side and a

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subtotal on the other, reoperation is easier since it now becomes a unilateral procedure (26). When patients are reoperated on for recurrence, total thyroidectomy or near-total thyroidectomy, in which the remnant size should be less than 2 g, is recommended (81). VIII. ADVANTAGES OF SURGERY The ideal treatment for Graves’ disease includes quick restoration and maintenance of the euthyroid state without relapse. Unfortunately antithyroid medications, radioiodine ablations, and thyroidectomy cannot routinely provide this outcome. The benefit of thyroidectomy is that it provides prompt relief of hyperthyroidism, and is the treatment most likely to render the patient euthyroid. Treatment with antithyroid medications also restores the euthyroid state in most patients, but it usually takes several weeks and long-term remission only occurs in about 30% of patients when the antithyroid medications are discontinued. The disadvantages of surgical treatment for Graves’ disease are that it requires an operation and hospitalization. The cost of surgical treatment is somewhat higher than that of radioiodine ablation, but it is comparable to antithyroid medication if the relapse costs are included (57). Ablative therapy for Graves’ disease such as thyroidectomy or radioiodine therapy can induce long-term remission in about 90% of cases. Recurrent hyperthyroidism is a potential risk with all treatment modalities. It is highest after treatment with antithyroid drugs. It is lowest after treatment with radioiodine, except where a low dose is used in which case persistent hyperthyroidism is common. Permanent hypothyroidism occurs most often after treatment with radioiodine. Hypothyroidism is rare after treatment with antithyroid drugs but overall recurrence of hyperthyroidism after antithyroid drug treatment is high: up to 70% (33,82,83). Rates of hyper- and hypothyroidism after surgery depend upon the extent of thyroidectomy. Subtotal thyroidectomy restores the euthyroid state quickly and maintains it in about 60% of patients, but a small percentage (⬍1%) may progress to hypothyroidism. Hypothyroidism is less frequent and recurrent hyperthyroidism is slightly more frequent after subtotal thyroidectomy than after radioiodine therapy. To avoid recurrent hyperthyroidism, total or near-total thyroidectomy is an alternative in high-risk and young patients. Graves’ ophthalmopathy may become aggravated after 131I therapy (59,60). Surgical treatment regardless of the extent of thyroidectomy, is rarely associated with postoperative aggravation of ophthalmopathy (20,24,33,64). Total thyroidectomy appears to be the preferred treatment for patients with active Graves’ ophthalmopathy, although more data are required to support this recommendation. Side effects of antithyroid drugs occur in 3–5% of patients and are usually mild. These include agranulocytosis (0.1–0.5% of patients) (84), severe hepatitis (85), vasculitis (86) rarely. With radioiodine therapy, short-term complications are minor and infrequent. It only minimally increases the risks of thyroid or nonthyroid cancers (51,65,87,88), but a recent investigation demonstrated significant increases in the incidence of and mortality from cancers of the small bowel and thyroid after 131I treatment (66). Thyroidectomy can be used in all age groups without these concerns. It can be used in cases of very large goiter, those associated with nodules, and those with relatively low iodine uptake. Advances in thyroid surgery have also reduced the frequency of serious complications, with rates now lower than 1% (27,37). Thus, total or near-total thyroidectomy is now a safe procedure when performed by experienced surgeons (18,23,27).

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Another advantage of thyroidectomy is that it provides tissue diagnosis of coexisting pathology, especially in the patients with thyroid nodules. Thyroidectomy is safe during the second trimester of pregnancy and in the elderly. By selecting subtotal, near-total, or total thyroidectomy based on what is best for a particular patient, optimal results can be obtained. Thyroidectomy is therefore the treatment of choice for children, pregnant women, patients with a large goiter, patients with coexistent thyroid cancer, patients with serious ophthalmopathy, and patients who refuse treatment with radioiodine or have allergic reaction to radioiodine. We believe that surgical treatment of Graves’ disease is currently underused in the United States despite its unique advantages. REFERENCES 1. DeGroot LJ, Larsen PR, Hennemann G. The Thyroid and Its Disease. 6th ed. New York: Churchill Livingstone, 1996. 2. Lind P, Langsteger W, Molnar M, Gallowitsch HJ, Mikosch P, Gomez I. Epidemiology of thyroid diseases in iodine sufficiency. Thyroid 1998; 8(12):1179–1183. 3. Stanbury JB, Ermans AE, Bourdoux P, Todd C, Oken E, Tonglet R, Vidor G, Braverman LE, Medeiros-Neto G. Iodine-induced hyperthyroidism: occurrence and epidemiology. Thyroid 1998; 8(1):83–100. 4. Bertelsen JB, Hegedu¨s L. Cigarette smoking and the thyroid. Thyroid 1994; 4(3):327–331. 5. Radosavljevic VR, Jankovic SM, Marinkovic JM. Stressful life events in the pathogenesis of Graves’ disease. Eur J Endocrinol 1996; 134(6):699–701. 6. Yoshiuchi K, Kumano H, Nomura S, Yoshimura H, Ito K, Kanaji Y, Ohashi Y, Kuboki T, Suematsu H. Stressful life events and smoking were associated with Graves’ disease in women, but not in men. Psychosom Med 1998; 60(2):182–185. 7. Nagasaka A, Nakai A, Oda N, Kotake M, Iwase K, Yoshida S. Reverse transcriptase is elevated in the thyroid tissue from Graves’ disease patients. Clin Endocrinol 2000; 53(2):155–159. 8. Luo G, Seetharamaiah GS, Niesel DW, Zhang H, Peterson JW, Prabhakar BS, Klimpel GR. Purification and characterization of Yersinia enterocolitica envelope proteins which induce antibodies that react with human thyrotropin receptor. J Immunol 1994; 152(5):2555–2561. 9. Zhang H, Kaur I, Niesel DW, Seetharamaiah GS, Peterson JW, Justement LB, Prabhakar BS, Klimpel GR. Yersinia enterocolitica envelope proteins that are crossreactive with the thyrotropin receptor (TSHR) also have B-cell mitogenic activity. J Autoimmun 1996; 9(4):509–516. 10. Feek CM, Sawers JS, Irvine WJ, Beckett GJ, Ratcliffe WA, Toft AD. Combination of potassium iodide and propranolol in preparation of patients with Graves’ disease for thyroid surgery. N Engl J Med 1980; 302(16):883–885. 11. Emerson CH, Anderson AJ, Howard WJ, Utiger RD. Serum thyroxine and triiodothyronine concentrations during iodide treatment of hyperthyroidism. J Clin Endocrinol Metab 1975; 40(1):33–36. 12. Rodier JF, Janser JC, Petit H, Schneegans O, Ott G, Kaissling A, Grob JC, Velten M. Effect of preoperative administration of Lugol’s solution on thyroid blood flow in hyperthyroidism Ann Chir 1998; 52(3):229–233. 13. Lee KS, Kim K, Hur KB, Kim CK. The role of propranolol in the preoperative preparation of patients with Graves’ disease. Surg Gynecol Obstet 1986; 162(4):365–369. 14. Tomaski SM, Mahoney EM, Burgess LP, Raines KB, Bornemann M. Sodium ipodate (oragrafin) in the preoperative preparation of Graves’ hyperthyroidism. Laryngoscope 1997; 107(8):1066–1070. 15. Takami H. Lithium in the preoperative preparation of Graves’ disease. Int Surg 1994; 79(1): 89–90. 16. Ozawa Y, Daida H, Shimizu T, Shishiba Y. Rapid improvement of thyroid function by using

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Park and Clark glucocorticoid indicated for the preoperative preparation of subtotal thyroidectomy in Graves’ disease. Endocrinol Jpn 1983; 30(1):93–100. Neimark II, Dudarev VA. Preoperative preparation with plasmapheresis of patients with diffuse toxic goiter and intolerance to antithyroid drugs. Probl Endokrinol 1986; 32(3):24–27. Hermann M, Roka R, Richter B, Freissmuth M. Early relapse after operation for Graves’ disease: postoperative hormone kinetics and outcome after subtotal, near-total, and total thyroidectomy. Surgery 1998; 124(5):894–900. Pelizzo MR, Bernante P, Toniato A, Piotto A, Grigoletto R. Hypoparathyroidism after thyroidectomy. Analysis of a consecutive, recent series. Minerva Chir 1998; 53(4):239–244. Marcocci C, Bruno-Bossio G, Manetti L, Tanda ML, Miccoli P, Iacconi P, Bartolomei MP, Nardi M, Pinchera A, Bartalena L. The course of Graves’ ophthalmopathy is not influenced by near-total thyroidectomy: a case–control study. Clin Endocrinol 1999; 51(4):503–508. Bergamini C, Borrelli A, Reddavide S, Borrelli D. The results of total thyroidectomy in Basedow’s disease. The authors’ personal experience of 180 cases. G Chir 2000; 21(4):160–166. Gough IR, Wilkinson D. Total thyroidectomy for management of thyroid disease. World J Surg 2000; (8):962–965. Miccoli P, Vitti P, Rago T, Iacconi P, Bartalena L, Bogazzi F, Fiore E, Valeriano R, Chiovato L, Rocchi R, Pinchera A. Surgical treatment of Graves’ disease: subtotal or total thyroidectomy? Surgery 1996; 120(6):1020. Linos DA, Karakitsos D, Papademetriou J. Should the primary treatment of hyperthyroidism be surgical? Eur J Surg 1997; 163(9):651–657. Razack MS, Lore JM Jr, Lippes HA, Schaefer DP, Rassael H. Total thyroidectomy for Graves’ disease. Head Neck 1997; 19(5):378–383. Alsanea O, Clark OH. Treatment of Graves’ disease: the advantages of surgery. Endocrinol Metab Clin North Am 2000; 29(2):321–337. Palit TK, Miller CC III, Miltenburg DM. The efficacy of thyroidectomy for Graves’ disease: a meta-analysis. J Surg Res 2000; 90(2):161–165. Ozaki O, Ito K, Mimura T, Sugino K, Ito K. Factors affecting thyroid function after subtotal thyroidectomy for Graves’ disease: case control study by remnant-weight matched-pair analysis. Thyroid 1997; 7(4):555–559. Sugino K, Mimura T, Ozaki O, Iwasaki H, Wada N, Matsumoto A, Ito K. Preoperative change of thyroid stimulating hormone receptor antibody level: possible marker for predicting recurrent hyperthyroidism in patients with Graves’ disease after subtotal thyroidectomy. World J Surg 1996; 20(7):801–807. Sugino K, Mimura T, Ozaki O, Kure Y, Iwasaki H, Wada N, Matsumoto A, Ito K. Early recurrence of hyperthyroidism in patients with Graves’ disease treated by subtotal thyroidectomy. World J Surg 1995; 19(4):648–652. Cusick EL, Krukowski ZH, Matheson NA. Outcome of surgery for Graves’ disease re-examined. Br J Surg 1987; 74(9):780–783. Okamoto T, Fujimoto Y, Obara T, Ito Y, Aiba M. Retrospective analysis of prognostic factors affecting the thyroid functional status after subtotal thyroidectomy for Graves’ disease. World J Surg 1992; 16(4):690. To¨rring O, Tallstedt L, Wallin G, Lundell G, Ljunggren JG, Taube A, Saä¨f M, Hamberger B. Graves’ hyperthyroidism: treatment with antithyroid drugs, surgery, or radioiodine—a prospective, randomized study. Thyroid Study Group. J Clin Endocrinol Metab 1996; 81(8):2986– 2893. Winsa B, Rastad J, Akerstro¨m G, Johansson H, Westermark K, Karlsson FA. Retrospective evaluation of subtotal and total thyroidectomy in Graves’ disease with and without endocrine ophthalmopathy. Eur J Endocrinol 1995; 132(4):406–412. Kasuga Y, Sugenoya A, Kobayashi S, Shimizu T, Onuma H, Shingu K, Asanuma K, Hama Y, Iida F. Significance of values of thyrotropin binding inhibitor immunoglobulins and appearance of intrathyroidal lymphocytes at subtotal thyroidectomy for Graves’ disease. J Am Coll Surg 1994; 178(6):589–594.

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36. Foster RS Jr. Morbidity and mortality after thyroidectomy. Surg Gynecol Obstet 1978; 146(3): 423–429. 37. Ro¨her HD, Goretzki PE, Hellmann P, Witte J. Complications in thyroid surgery. Incidence and therapy. Chirurg 1999; 70(9):999–1010. 38. Rieu M, Richard A, Sadoudi R, Berrod JL. Effects of thyroid status on thyroid autoimmunity expression in surgically induced hypothyroid patients with Graves’ disease. Hormone Res 1995; 44(1):29–34. 39. Kasuga Y, Kobayashi S, Fujimori M, Shingu K, Asanuma K, Hama Y, Ito K, Maruyama M, Amano J. Changes in thyroid function and immunological parameters long after subtotal thyroidectomy for Graves’ disease. Eur J Surg 1998; 164(3):173–178. 40. Simms JM, Talbot CH. Surgery for thyrotoxicosis. Br J Surg 1983; 70(10):581–583. 41. Sugrue DD, Drury MI, McEvoy M, Heffernan SJ, O’Malley E. Long term follow-up of hyperthyroid patients treated by subtotal thyroidectomy. Br J Surg 1983; 70(7):408–411. 42. Becks GP, Burrow GN. Thyroid disease and pregnancy. Med Clin North Am 1991; 75(1): 121–150. 43. Stice RC, Grant CS, Gharib H, van Heerden JA. The management of Graves’ disease during pregnancy. Surg Gynecol Obstet 1984; 158(2):157–160. 44. Sugino K, Ito K, Ozaki O, Mimura T, Iwasaki H, Wada N. Postoperative changes in thyrotropin-binding inhibitory immunoglobulin level in patients with Graves’ disease: is subtotal thyroidectomy a suitable therapeutic option for patients of childbearing age with Graves’ disease? World J Surg 1999; 23(7):727–731. 45. Clavel S, Madec AM, Bornet H, Deviller P, Stefanutti A, Orgiazzi J. Anti TSH-receptor antibodies in pregnant patients with autoimmune thyroid disorder. Br J Obstet Gynaecol 1990; 97(11):1003–1008. 46. Zimmerman D. Fetal and neonatal hyperthyroidism. Thyroid 1999; 9(7):727–733. 47. Barnes HV, Blizzard RM. Antithyroid drug therapy for toxic diffuse goiter (Graves disease): thirty years experience in children and adolescents. J Pediatr 1977; 91(2):313–320. 48. Boiko J, Le´ger I, Raux-Demay MC, Cabrol S, Le Bouc Y, Czernichow P. Basedow disease in children: clinical and evolutive aspects. Arch Pediatr 1998; 5(7):722–730. 49. Raza J, Hindmarsh PG, Brook CG. Thyrotoxicosis in children: thirty years’ experience. Acta Paediatr 1999; 88(9):937–941. 50. Ikenoue H, Okamura K, Sato K, Kuroda T, Yoshinari M, Tokuyama T, Nakagawa M, Fujishima M. Prediction of relapse in drug-treated Graves’ disease using thyroid stimulation indices. Acta Endocrinol 1991; 125(6):643–650. 51. Franklyn JA, Maisonneuve P, Sheppard MC, Betteridge J, Boyle P. Mortality after the treatment of hyperthyroidism with radioactive iodine. N Engl J Med 1998; 338(11):712–718. 52. Esselstyn CB Jr, Schumacher OP, Eversman J, Sheeler L, Levy WJ. Hyperparathyroidism after radioactive iodine therapy for Graves disease. Surgery 1982; 92(5):811–813. 53. Freitas JE, Swanson DP, Gross MD, Sisson JC. Iodine-131: optimal therapy for hyperthyroidism in children and adolescents? J Nucl Med 1979; (8):847–850. 54. Moll GW Jr, Patel BR. Pediatric Graves’ disease: therapeutic options and experience with radioiodine at the University of Mississippi Medical Center. South Med J 1997; 90(10):1017– 1022. 55. O’Neill JA, Row MI, Grosfeld JL, Fonkalsrud EW, Coran AG. Pediatric Surgery. 5th ed. St. Louis: CV Mosby, 1998:746–747. 56. So¨reide JA, van Heerden JA, Lo CY, Grant CS, Zimmerman D, Ilstrup DM. Surgical treatment of Graves’ disease in patients younger than 18 years. World J Surg 1996; 20(7):794–799. 57. Ljunggren JG, To¨rring O, Wallin G, Taube A, Tallstedt L, Hamberger B, Lundell G. Quality of life aspects and costs in treatment of Graves’ hyperthyroidism with antithyroid drugs, surgery, or radioiodine: results from a prospective, randomized study. Thyroid 1998; 8(8):653– 659. 58. Bartalena L, Pinchera A, Marcocci C. Management of Graves’ ophthalmopathy: reality and perspectives. Endocr Rev 2000; 21(2):168–199.

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59. Bartalena L, Marcocci C, Bogazzi F, Manetti L, Tanda ML, Dell’Unto E, Bruno-Bossio G, Nardi M, Bartolomei MP, Lepri A, Rossi G, Martino E, Pinchera A. Relation between therapy for hyperthyroidism and the course of Graves’ ophthalmopathy N Engl J Med 1998; 338(2): 73–78. 60. Tallstedt L, Lundell G. Radioiodine treatment, ablation, and ophthalmopathy: a balanced perspective. Thyroid 1997; 7(2):241–245. 61. Tallstedt L, Lundell G, Tørring O, Wallin G, Ljunggren JG, Blomgren H, Taube A. Occurrence of ophthalmopathy after treatment for Graves’ hyperthyroidism. The Thyroid Study Group. N Engl Med 1992; 326(26):1733–1738. 62. Kung AW, Yau CC, Cheng A. The incidence of ophthalmopathy after radioiodine therapy for Graves’ disease: prognostic factors and the role of methimazolee. J Clin Endocrinol Metab 1994; 79(2):542–546. 63. Wiersinga WM. Preventing Graves’ ophthalmopathy. N Engl J Med 1998; 338(2):121–122. 64. Abe Y, Sato H, Noguchi M, Mimura T, Sugino K, Ozaki O, Yoshimura H, Ito K. Effect of subtotal thyroidectomy on natural history of ophthalmopathy in Graves’ disease. World J Surg 1998; 22(7):714–717. 65. Dobyns BM, Sheline GE, Workman JB, Tompkins EA, McConahey WM, Becker DV. Malignant and benign neoplasms of the thyroid in patients treated for hyperthyroidism: a report of the cooperative thyrotoxicosis therapy follow-up study. J Clin Endocrinol Metab 1974; 38(6): 976–998. 66. Franklyn JA, Maisonneuve P, Sheppard M, Betteridge J, Boyle P. Cancer incidence and mortality after radioiodine treatment for hyperthyroidism: a population-based cohort study. Lancet 1999; 353(9170):2111–2115. 67. Ron E, Doody MM, Becker DV, Brill AB, Curtis RE, Goldman MB, Harris BS III, Hoffman DA, McConahey WM, Maxon HR, Preston-Martin S, Warshauer ME, Wong FL, Boice JD Jr. Cancer mortality following treatment for adult hyperthyroidism. Cooperative Thyrotoxicosis Therapy Follow-up Study Group. JAMA 1998; 280(4):347–355. 68. Behar R, Arganini M, Wu TC, McCormick M, Straus FH II, DeGroot LJ, Kaplan EL. Graves’ disease and thyroid cancer. Surgery 1986; 100(6):1121–1127. 69. Kraimps JL, Bouin-Pineau MH, Marećhaud R, Barbier J. Basedow’s disease and thyroid nodules. A common association. Ann Chir 1998; 52(5):449–451. 70. Kraimps JL, Bouin-Pineau MH, Mathonnet M, De Calan L, Ronceray J, Visset J, Marechaud R, Barbier J. Multicentre study of thyroid nodules in patients with Graves’ disease. Br J Surg 2000; 87(8):1111–1113. 71. Ozaki O, Ito K, Kobayashi K, Toshima K, Iwasaki H, Yashiro T. Thyroid carcinoma in Graves’ disease. World J Surg 1990; 14(3):437. 72. Pacini F, Elisei R, Di Coscio GC, Anelli S, Macchia E, Concetti R, Miccoli P, Arganini M, Pinchera A. Thyroid carcinoma in thyrotoxic patients treated by surgery. J Endocrinol Invest 1988; 11(2):107–112. 73. Vaiana R, Cappelli C, Perini P, Pinelli D, Camoni G, Farfaglia R, Balzano R, Braga M. Hyperthyroidism and concurrent thyroid cancer. Tumori 1999; 85(4):247–252. 74. Carnell NE, Valente WA. Thyroid nodules in Graves’ disease: classification, characterization, and response to treatment. Thyroid 1998; 8(8):647–652. 75. Joseph UA, Jhingran SG. Graves’ disease and concurrent thyroid carcinoma. The importance of thyroid scintigraphy in Graves’ disease. Clin Nucl Med 1995; 20(5):416–418. 76. Belfiore A, Garofalo MR, Giuffrida D, Runello F, Filetti S, Fiumara A, Ippolito O, Vigneri R. Increased aggressiveness of thyroid cancer in patients with Graves’ disease. J Clin Endocrinol Metab 1990; 70(4):830–835. 77. Pellegriti G, Belfiore A, Giuffrida D, Lupo L, Vigneri R. Outcome of differentiated thyroid cancer in Graves’ patients. J Clin Endocrinol Metab 1998; 83(8):2805–2809. 78. Hales IB, McElduff A, Crummer P, Clifton-Bligh P, Delbridge L, Hoschl R, Poole A, Reeve TS, Wilmshurst E, Wiseman J. Does Graves’ disease or thyrotoxicosis affect the prognosis of thyroid cancer. J Clin Endocrinol Metab 1992; 75(3):886–889.

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20 Overview of Thyroid Eye Disease: Immunological Mechanisms JONATHAN J. DUTTON Atlantic Eye and Face Center, Cary, and University of North Carolina, Chapel Hill, North Carolina, U.S.A.

I.

INTRODUCTION

Immune-mediated inflammatory processes usually occur in response to foreign antigens: immune cells recognize structures and molecular signals that are different from ‘‘self’’ (1). Under certain circumstances, however, such processes occur in the apparent absence of foreign antigens, and host tissue becomes involved by a destructive immune reaction, known as an autoimmune disease. Graves’ disease is a chronic autoimmune disorder of uncertain cause. Robert Graves first described it clinically in 1835, although probable cases were mentioned by other authors earlier. Yet it has only been in the past two decades that we have begun to understand the immunological basis for this disease, as well as for other chronic autoimmune disorders (1). Although many questions remain to be answered and numerous controversies need to be clarified, it now appears certain that the thyroidal and extrathyroidal manifestations associated with Graves’ disease are related to T-cell activation and immunological interaction with specific tissue antigens. In Graves’ disease, pathological development is influenced by genetic, hormonal, environmental, and perhaps other factors (2). The immunological model for organ-specific autoimmune diseases presumes T-cell recognition of a peptide processed by antigenpresenting cells residing in the disease compartment, with subsequent activation of the immune system. This requires the participation of costimulatory molecules and results in the recruitment of other immune cells with release of various cytokines. These cytokines act to propagate the local immune response and to stimulate particular metabolic, immune, and proliferative functions of the target cells. Such processes result in characteristic pathological changes specific to the autoimmune disease and tissue (3). 199

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II. PRIMARY GRAVES’ DISEASE The pathophysiology of autoimmune disease in the thyroid gland is not entirely clear. Dendritic and other antigen-presenting cells (APC) are attracted to the thyroid, perhaps related to antigens of viral or bacterial origin, or perhaps to cellular debris released by toxic agents. These APCs travel from the thyroid gland to the draining lymph nodes where they present thyroid antigens to T cells. Here, for reasons that remain unknown, selftolerance is lost and the autoimmune response is initiated (4). In Graves’ disease the thyroid gland often shows areas of focal thyroiditis, similar to that seen in Hashimoto’s disease (5). These consist of organized lymphoid tissue located adjacent to stimulated thyroid follicles (6). The architecture of this lymphoid tissue is similar to mucosa-associated lymphoid tissue (MALT), and has been referred to as thyroidassociated lymphoid tissue (TALT). In the animal model, TALT presents weeks after the appearance of thyroid autoantibodies in the circulation. Cytokines produced in the TALT are believed to induce the expression of major histocompatibility complex (MHC) class II molecules on neighboring thyrocytes (7). It seems likely that the TALT is involved in thyroid autoantibody production as well as in the local generation of autoreactive T cells. The development of TALT depends upon the formation of special high endothelial venules normally present in lymph tissues and MALT, which allow the homing of lymphocytes into the tissue. Their development in the thyroid gland facilitates the influx of autoreactive lymphocytes initiated in the draining lymph nodes (8). This homing concerns the trafficking of naı¨ve cells and memory/effector populations that display tissue-selective patterns of recirculation to sites where they are likely to re-encounter their specific antigen (1). In this regard, trafficking of leukocytes is influenced by soluble mediators secreted by endothelial cells, including chemokines that may selectively encourage transmigration of certain types of T cell (9), and by a complex signaling cascade mediated by surface-expressed adhesion molecules (10,11). Once T cells are activated, they initiate a number of effector functions, such as the activation of other effector cells via various signaling molecules including cytokines. In addition to signaling other types of cells, cytokines can also affect the T cells themselves, most notably proliferation and activation of additional T cells that amplify the immune reaction (1). It seems well established that the primary target of the autoimmune reaction in Graves’ disease is the thyroid-stimulating hormone (TSH) receptor on the thyrocyte. The large extracellular domain of the TSH receptor (TSHR) is the target for thyrotropin, TSHR antibodies, and for immune effector cells. It plays a central role in TSHR function and immune recognition. The anti-TSHR–T-cell interaction with this receptor activates thyroid hormone production independent of the hypothalamic–pituitary–thyroid axis. Various TSHR-blocking antibodies and cytotoxic antibodies directed against other thyrocyte cellular components may supervene to result in variations in patient response, and also may explain the variant of euthyroid Graves’ disease.

III. THYROID EYE DISEASE Graves’ disease is associated with several extrathyroidal manifestations. Pretibial myxedema is a diffuse or circumscribed form of mucinous dermopathy occurring in a small proportion of patients with severe ophthalmopathy and high serum titers of thyrotropin receptor antibodies (12). Certainly the major extrathyroidal manifestation is thyroid eye

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disease, an inflammatory process involving multiple orbital tissues. The earliest systematic account of the natural history of the orbital disease is attributed to Rundle (13). The typical orbital findings include periorbital edema, conjunctival injection, eyelid retraction, proptosis, and restrictive ophthalmoplegia. All of these signs are directly related to inflammation in specific retro-orbital tissues that eventuate in anatomical changes. In addition, a number of orbital findings result as secondary manifestations stemming from the primary anatomical alterations. Within this group, in rare cases, is compressive optic neuropathy resulting from enlarged extraocular muscles in the posterior orbit. Corneal exposure and ulceration can likewise be associated with severe eyelid retraction and impaired blink reflex. Congestive orbitopathy from compression of the superior ophthalmic and other veins can inhibit vascular outflow and cause a secondary type of glaucoma that can be refractory to usual therapeutic regimens. Both extrathyroidal inflammatory processes are likely driven by T cells that access and infiltrate the orbital and pretibial space via certain adhesion molecules (14); with the release of various cytokines capable of stimulating cell proliferation, glycosaminoglycan synthesis, and expression of immunomodulatory molecules in microvascular endothelial cells, dendritic cells, and fibroblasts (15–18) (Fig. 1). Trafficking and homing patterns of thyroid-reactive T lymphocytes may also play a role in the orbital disease. Selective homing patterns are thought to exist for thyroid-reactive lymphocytes to the draining lymph

Figure 1 Diagrammatic and highly simplified schema of likely events mediating the immune response in Graves’ orbital disease. Stimulation of Th-1 lymphocytes (T) by antigen-presenting cells (apc) activates the autoimmune reaction targeted against the TSH-receptor on the thyrocyte, resulting in a hyperthyroid response. Homing and migration of activated T cells across vascular endothelial cells (ec) into secondary target sites, such as the orbit, occurs under the influence of various vascular and intercellular adhesion molecules. Interaction with secondary TSHR epitopes, presumably on the orbital fibroblast (OF), results in the release of chemokines, cytokines, growth factors, and proinflammatory mediators that initiate the immune reaction, recruit and activate additional inflammatory T cells, and initiate a series of effector cell responses that result in tissue edema, fibrosis, and the manifestations of thyroid eye disease.

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nodes (superior deep cervical nodes) and the thyroid gland. These lymphocytes might carry addressins and other homing molecules recognized by structures on thyroidal and thyroid–lymph nodal vessels. Periorbital and perhaps some deep orbital tissues share the superior deep cervical draining lymph nodes with the thyroid gland, and such T cells may preferentially home to the orbit. Evidence strongly supports the concept of shared antigenic proteins between the thyrocyte and certain secondary target tissues. Over the past several decades a number of candidates have been proposed for this shared target antigen in the orbit. While certain extraocular muscle antigens appear to be targeted by autoantibodies in Graves’ disease (19), and while these certainly contribute to the overall picture of the orbital disease, it has still not been demonstrated whether these antibodies are primary to the disease or secondary to other adjacent inflammatory processes. Orbital fibroblasts in the endomysium and perimysium of the extraocular muscles express MHC class II molecules, suggesting that they are prime targets of the autoimmune attack in the orbit. Focal organized accumulations of lymphocytes similar to the TALT structures in the thyroid gland are also present (20). To date, the most likely candidate for the primary immunological target is the retroorbital preadipocyte fibroblast-like cell (21,22). It is also well established that orbital fibroblasts display immunological differences compared to most dermal fibroblasts (21,22). For example, interferon-gamma (INF-γ) and leukoregulin selectively upregulate hyaluronan accumulation in orbital fibroblasts, and they express a characteristic profile of receptors, gangliosides, cytokines, and patterns of protein induction (23–28). Also, preadipocyte fibroblasts appear to occur only within the orbital fibroblast population (29). These cells are capable of undergoing adipocyte differentiation, which contributes to the overall orbital volume augmentation so characteristic of thyroid eye disease (30). RNA transcripts and proteins representing extracellular domain TSHR are expressed in orbital preadipocytes and some pretibial fibroblasts (31). These orbital TSHR antigens are present in patients with thyroid eye disease, while they are absent in normal orbital tissues (32). Thus, it now seems probable that the orbital preadipocyte fibroblast expresses the TSHR antigen and that an autoimmune response to this effector cell is the initiating event in thyroid eye disease (33). Interactions between target orbital fibroblasts and immunocompetent cells that infiltrate the orbit are thought to be important in the pathogenesis of the orbital changes (16). The initial insult in Graves’ orbital disease involves the production of chemokines or migration and homing molecules as well as intercellular and vascular endothelial cell adhesion molecules (ICAM, VCAM) (11). These encourage further infiltration of activated T-cell lymphocytes into the inflammatory site. The ensuing antigen–antibody interaction releases a variety of chemical proinflammatory factors. Inflammatory mediators such as prostaglandin E2, nitric oxide, histamine, and specific proteases result in lymphatic relaxation, valve incompetence and stasis, as well as vascular dilatation, increased vascular permeability, and tissue edema. Transforming growth factors such as TGF-β stimulate further T-cell proliferation. Studies have shown that retro-orbital infiltrates of patients with thyroid eye disease contain cytolytic T cells with a Th1 cytokine profile similar to that found in the thyroid gland of Graves’ patients (34). These clones secrete interleukin-2 (IL-2), interferon-γ (INF-γ), and tissue necrosis factor-α (TNF-α), but not IL-4 or IL-5. This profile seems capable of initiating alterations in the orbital fibroblast such as collagen synthesis (35,36), glycosaminoglycan accumulation (36,37), increased susceptibility to IFN-γ-induced major


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histocompatibility complex class II antigen expression (38), and membrane expression of heat shock protein (39). Also, INF-γ and TNF-α can induce or enhance the expression of HLA-DR molecules to a greater extent in retro-orbital fibroblasts from Graves’ patients than in those from normal individuals (38). This antigen is a key factor in the induction and perpetuation of the autoimmune process. It is controlled by a gene that is found in higher frequency among patients with Graves’ disease than in normals, and may represent a genetic predisposition. The glycosaminoglycans (GAGs) accumulate throughout the orbit, resulting in increased thickness of extraocular muscles. The nature of these GAGs has been shown to differ from those in normal orbits, making them more hydrophilic; the resulting water binding causes increased tissue edema and is a major factor in the development of proptosis (40,41). Increased collagen synthesis and deposition result in thickening of fascial connective tissue systems causing adipose tissue interlobular fascial fibrosis, thickening of extraocular muscle sheaths and interfascicular membranes. This results in eventual restrictive myopathy, and contraction and scarring of eyelid suspensory ligaments leading to eyelid retraction. Cell-mediated cytotoxic activity has been demonstrated recently against Mu¨ller’s supratarsal muscle, perhaps further contributing to the eyelid retraction characteristic of this disease (42). IV.

EMERGING THERAPEUTIC OPTIONS

Armed with this emerging picture of the immunological mechanisms responsible for orbital pathology in patients with Graves’ disease, the next decade should witness new and innovative therapeutic approaches undreamed of only a few years ago. These will be targeted toward specific points along the immunological pathway. For example, immunomodulation of specific T-cell receptor sites might block the ability of activated T cells to bind to TSHR antigens. It may be possible to block antigen-presenting cell receptor sites, thus preventing T-cell activation. Some early work has been done in the engineering of a soluble human TSHR-neutralizing antigen (43). Cytokine modulation is probably the most imminent therapeutic option (44–46). Included in this are cytokine antagonists, cytokine-binding proteins, and cytokines that block other cytokines. Studies have demonstrated that interleukin-1α–induced GAG production by retro-orbital fibroblasts can be inhibited by recombinant IL-1 receptor antagonists and by soluble IL-1 receptors, suggesting that IL-1 antagonism might be therapeutically successful in patients with thyroid eye disease (47). Pentoxyfilline is known to have an effect on the production of cytokines. In early trials it has been shown to inhibit the release and activity of IL-1, INF-γ, and TNF-α and to inhibit the expression of HLA-DR and GAG synthesis induced by inflammatory cytokines in patients with thyroid eye disease (48–50). Finally, the long-acting somatostatin analogs octreotide and lanreotide have been shown in vitro and in vivo to inhibit the production of GAG and Th1 cytokine release (51–53). V. CONCLUSION Graves’ orbital disease is a secondary immunological manifestation of the primary antithyroid autoimmune disease. T-cell-mediated reactions are initiated probably through expression of TSHR epitopes located on the orbital preadipocyte fibroblast, and perhaps other cells. Release of proinflammatory mediators, chemokines, and a Th1-like cytokine profile

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induce effector cell proliferation and elaboration of GAG, collagen, and other products that contribute to the overall pathological picture. Armed with this emerging concept of immunological mechanisms operating in the orbit, new and exciting new therapeutic modalities are arising that may soon prevent the sometimes devastating visual consequences of this common disease. REFERENCES 1. Van Noort JM, Amor S. Cell biology of autoimmune diseases. Int Rev Cytol 1998; 178:127– 206. 2. Heufelder AE. Retro-orbital autoimmunity. Bailliers Clin Endocrinol Metab 1997; 11:499– 520. 3. Bahn RS. Cytokines in thyroid eye disease: potential for anticytokine therapy. Thyroid 1998; 8:415–418. 4. Delemarre FGA, Simons PJ, Drexhage HA. Histomorphological aspects of the development of thyroid autoimmune diseases: consequences for our understanding of endocrine ophthalmopathy. Thyroid 1996; 6:369–377. 5. Kabel PJ, Voorbij HAM, Haan-Meulman M de, Gaag RD van der, Drexhage HA. Intrathyroidal dendritic cells. J Clin Endocrinol Metab 1988; 65:199–207. 6. Pachke R, Bruckner N, Eck T, Back W, Usadel KH. Regional stimulation of thyroid epithelial cells in Graves’ disease by lymphocytic aggregates and plasma cells. Acta Endocrinol 1991; 125:459–465. 7. Weetman AP. The potential role of the thyroid cell in autoimmune thyroid disease. Thyroid 1994; 4:493–539. 8. Kabel PJ, van Dinther A, Haan-Meulman M de, Berghout A, Voorbij HAM, Drexhage HA. A diminished adherence of blood lymphocytes of patients with thyroid autoimmune disease to high endothelial venules in the thyroid and thyroid-draining lymph nodes. Autoimmunity 1990; 5:247–256. 9. Del Pozo MA, Mateo S, Sanchez-Madrid F. Cellular polarization induced by chemokines: a mechanism for leukocyte recruitment? Immunol Today 1996; 17:127–130. 10. Springer TA. Adhesion molecules of the immune system. Nature (London) 1990; 346:425– 434. 11. Madri JA, Graesser D, Haas T. The roles of adhesion molecules and proteinases in lymphocyte transendothelial migration. Cell Biol 1996; 74:749–757. 12. Fatourechi V, Pajouhi M, Fransway FA. Dermopathy of Graves’ disease (pretibial myxedema). Medicine 1994; 73:1–7. 13. Rundle FF, Wilson CW. Development and course of exophthalmos and ophthalmoplegia in Graves’ disease with special reference to the effect of thyroidectomy. Clin Sci 1945; 5:177– 194. 14. McMurray RW. Adhesion molecules in autoimmune disease. Semin Arthritis Rheum 1996; 25:215–233. 15. Burch HB, Wartofsky L. Graves’ ophthalmopathy: current concept regarding pathogenesis and management. Endocr Rev 1993; 14:747–793. 16. Bahn RS, Heufelder A. Mechanisms of diseases: pathogenesis of Graves’ ophthalmopathy. N Eng J Med 1993; 329:1468–1475. 17. Weetman AP. Thyroid associated eye disease: pathophysiology. Lancet 1991; 338:25–32. 18. Heufelder A, Wenzel BE, Scriba PC. Antigen receptor variable region repertoires expressed by T cells infiltrating thyroid, retroorbital and pretibial tissue in Graves’ disease. J Clin Endocrinol Metab 1996; 81:3733–3739. 19. Kubota S, Gunji K, Stolarski JS, Kennerdell JS, Wall J. Reevaluation of the prevalence’s of serum autoantibodies reactive with ‘‘64-kd eye muscles proteins’’ in patients with thyroidassociated ophthalmopathy. Thyroid 1998; 8:175–179.


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20. Weetman AP, Cohen S, Gatter KC, Fells P, Shine B. Immunohistochemical analysis of the retrobulbar tissues in Graves’ ophthalmopathy. Clin Exp Immunol 1989; 75:222–227. 21. Bahn R, Heufelder AE. Retroocular fibroblasts: important effector cells in Graves’ Ophthalmopathy. Thyroid 1992; 2:89–94. 22. Heufelder AE, Bahn RS. Evidence for the presence of functional TSH-receptor in retroocular fibroblasts from patients with Graves’ ophthalmopathy. Exp Clin Endocrinol 1992; 100:62– 67. 23. Smith TJ, Wang H-S, Hogg MG, Henrikson RC, Keese CR, Giaever I. Prostaglandin E2 elicits a morphological change in cultured orbital fibroblasts from patients with Graves’ ophthalmopathy. Proc Natl Acad Sci USA 1994; 91:5094–5098. 24. Smith TJ, Ahmed A, Hogg MG, Higgins PJ. Interferon gamma is an inducer of plasminogen activator inhibitor type 1 in human orbital fibroblasts. Am J Physiol 1992; 263:C24–C29. 25. Smith TJ, Higgins PJ. Interferon gamma regulation of de novo protein synthesis in human dermal fibroblasts in culture is anatomic site dependent. J Invest Dermatol 1993; 100:288– 292. 26. Smith TJ, Kottke RJ, Lum H, Anderson TT. Human orbital fibroblasts in culture bind and respond to endothelin. Am J Physiol 1993; 265:C138–C142. 27. Hogg MG, Evans CH, Smith TJ. Leukoregulin indiuces plasminogen activator inhibitor type 1 in human orbital fibroblasts. Am J Physiol 1995; 269:C359–C366. 28. Berenson CS, Smith TJ. Human orbital fibroblasts in culture express gangliosides profiles distinct from those in dermal fibroblasts. J Clin Endocrinol Metab 1995; 80:2668–2674. 29. Smith TJ, Sempoeski GD, Wang H-S, DelVecchio PJ, Lippe SD, Phipps RP. Evidence for cellular heterogeneity in primary cultures of human fibroblasts. J Clin Endocrinol Metab 1995; 80:2620–2625. 30. Sorisky A, Pardasani D, Gagnon A, Smith TJ. Evidence of adipocyte differentiation in human orbital fibroblasts in primary culture. J Clin Endocrinol Metab 1996; 81:3428–3431. 31. Stadlmayr W, Spitzweg C, Bichlmair A-M, Heufelder AE. TSH receptor transcripts and TSH receptor-like immunoactivity in orbital and pretibial fibroblasts of patients with Graves’ ophthalmopathy and pretibial myxedema. Thyroid 1997; 7:3–12. 32. Bahn RS, Dutton CM, Natt N, Joba C, Spitzweg C, Heufelder AE. Thyrotropin receptor expression in Graves’ orbital adipose/connective tissues: potential autoantigens in Graves’ ophthalmopathy. J Clin Endocrinol Metab 1998; 83:998–1002. 33. Ludgate M, Crist M, Lane C, Costagliola S, Vassart G, Weetman A, Daunerie C, Many MC. The thyrotropin receptor in thyroid eye disease. Thyroid 1998; 8:411–413. 34. Carli M de, D’Elois MM, Mariotti S, et al. Cytolytic T cells with Th-1 like cytokine profile predominate in retroorbital lymphocytic infiltrates of Graves’ ophthalmopathy. J Clin Endocrinol Metab 1993; 77:1120–1124. 35. Wall JR, Salvi M, Bernard NF, Boucher A, Haegert D. Thyroid-associated ophthalmopathy: a model for the association of organ-specific autoimmune disorders. Immunol Today 1991; 12:150–153. 36. Stover C, Otto E, Beyer J, Kahaly G. Cellular immunity and retrobulbar fibroblasts in Graves’ ophthalmopathy. Thyroid 1994; 4:161–165. 37. Smith TS, Bahn RS, Gorman CA, Cheavens M. Stimulation of glycosaminoglycan accumulation by interferon-gamma in cultured human retroocular fibroblasts. J Clin Endocrinol Metab 1991; 72:1167–1171. 38. Heufelder AE, Smith TJ, Gorman CA, Bahn RS. Increased induction of HLA-DR by interferon-γ in cultured fibroblasts derived from patients with Graves’ ophthalmopathy and pretibial dermopathy. J Clin Endocrinol Metab 1991; 73:307–313. 39. Heufelder AE, Wenzel BE, Bahn RS. Cell surface localization of a 72 kilodalton heat shock protein in retroocular fibroblasts from patients with Graves’ ophthalmopathy. J Clin Endocrinol Metab 1992; 74:732–736. 40. Hansen C, Otto E, Kuhlemann K, Fo¨rster G, Kahaly G. Glycosaminoglycans in autoimmunity. Clin Exp Rheumatol 1996; 14:59–67.

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41. Kahaly G, Hansen C, Stover C, Kuhlemann K, Beyer J, Otto E. Glycosaminoglycans and endocrine orbitopathy. Exp Clin Endocrinol 1994; 102:151–161. 42. Barsouk A, Peele KA, Kiljanski J, Stolarski C, Nebes V, Kennerdell JS, Volpe R, Wall JR. Antibody-dependent cell-mediated cytotoxicity against orbital target cells in thyroidassociated ophthalmopathy and related disorders; close relationship between serum cytotoxic antibodies and parameters of eye muscle dysfunction. J Endocrinol Invest 1996; 19: 334–341. 43. Chazenbalk GD, Jauma JC, McLachlan SM, Rappaport B. Engineering the human thyrotropin receptor ectodomain from a non-secretory for to a secreted, highly immunoreactive glycoprotein that neutralizes autoantibodies in Graves’ patients’ sera. J Biol Chem 1997; 272:18959– 18965. 44. Bahn RS. Cytokines in thyroid eye disease: potential for anticytokine therapy. Thyroid 1998; 8:415–418. 45. Weckmann AL, Alcocer-Valela J. Cytokine inhibitors in autoimmune disease. Semin Arthritis Rheum 1996; 26:539–557. 46. Weckmann AL, Alcocer-Varela J. Cytokine inhibitors in autoimmune disease. Semin Arthritis Rheum 1996; 26:539–557. 47. Tan GH, Dutton CM, Bahn RS. Interleukin-1 receptor antagonist and soluble interleukin-1 receptor inhibit interleukin-1 glycosaminoglycan production in cultured human orbital fibroblasts from patients with Graves’ ophthalmopathy. J Clin Endocrinol Metab 1995; 81:449– 452. 48. Balazs C, Kiss E, Vamos A, Molnar I, Farid NR. Immunomodulatory effect of pentoxifylline in Graves’ ophthalmopathy. Orv Hetil 1997; 138:2869–2874. 49. Balazs C, Kiss E, Vamos A, Molnar I, Farid NR. Beneficial effect of pentoxifylline on thyroid associated ophthalmopathy (TAO): a pilot study. J Clin Endocrinol Metab 1997; 82:1999– 2001. 50. Chang C, Chang TC, Kao YF, Chien LF. Pentoxifylline inhibits the proliferation and glycosaminoglycans synthesis of cultured fibroblasts derived from patients with Graves’ ophthalmopathy and pretibial myxedema. Acta Endocrinol (Copenh) 1993; 129:322–327. 51. Krassas GE. Somatostatin analogues in the treatment of thyroid eye disease. Thyroid 1998; 8:443–445. 52. Uyal AR, Corapcioglu D, Tonyukuk VC, Gullu VC, Sac H, Kamel N, Erdogan G. Effect of octreotide treatment on Graves’ ophthalmopathy. Endocr J 1999; 46:573–577. 53. Wiersinga WM, Gerding MN, Prummel MF, Krenning EP. Octreotide scintigraphy in thyroidal and orbital Graves’ disease. Thyroid 1998; 8:433–436.

21 Orbital Fibroblasts and the TSH Receptor in Graves’ Orbital Disease ARMIN E. HEUFELDER and WERNER JOBA Clinical Research Center, Munich, Germany

I.

INTRODUCTION

Graves’ disease (GD) is an autoimmune syndrome characterized by hyperthyroidism and a diffusely enlarged thyroid gland. The most prominent extrathyroidal manifestation of this thyroid disease is thyroid-associated or Graves’ ophthalmopathy (GO), a medically incurable and chronic autoimmune process that affects all orbital tissue compartments and leads to various eye complications such as discomfort, lid edema and retraction, proptosis, extraocular muscle dysfunction, diplopia, and sight loss. Various degrees of GO occur in 80–90% of patients with GD. In most instances, the orbital problems appear within 18 months after diagnosis of thyroid disease. The close clinical association of GD with GO and pretibial dermopathy (PTD), a less frequent extrathyroidal manifestation, suggests a common antigen for these affected tissues (1,2). Enlargement of extraocular muscle bodies together with an increase of orbital connective/fatty tissue within the bony orbits is responsible for most of the orbital problems in patients with severe active GO. This enlargement is caused by marked infiltration of immunocompetent cells, such as macrophages, T lymphocytes and some B cells, and by abundant quantities of collagen and hydrophilic glycosaminoglycans (GAGs). The inflammatory process is likely to be driven by T cells, which access and infiltrate the retro-orbital space after interaction with several adhesion molecules. Once recruited, T cells release numerous cytokines capable of stimulating cell proliferation, GAG synthesis, recruitment of new fat cells from orbital adipose precursor cells, and expression of various immunomodulatory molecules by orbital preadipocyte fibroblasts (3). Although these mechanisms may sufficiently explain various aspects of how GO may evolve and be propagated, the primary antigen for this autoimmune process has remained elusive. 207

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II. THYROID-STIMULATING HORMONE RECEPTOR: A LINK BETWEEN THE THYROID AND ORBIT IN GRAVES’ DISEASE? In recent years, significant efforts have been made to define the nature of the target autoantigen in GO. The hyperthyroidism of Graves’ disease results from uncontrolled stimulation of the thyroid-stimulating hormone receptor (TSHR) by antibodies directed against this autoantigen, which mimic the action of TSH by increasing intracellular cyclic adenosine monophosphate (cAMP) levels. This leads to increased thyrocyte function and growth, independent of the hypothalamic–pituitary–thyroid axis. Clinically, a close temporal relationship between the onset of GD and development of extrathyroidal manifestations, such as GO, PTD, or acropachy, is observed. Although a close correlation between the presence of TSHR-directed antibodies and the presence or severity of GO has not definitively been established, patients with GO and PTD almost uniformly display high titers of TSHRstimulating antibodies (TSAb). Moreover, severe GO frequently occurs in the presence of high concentrations of TSHR-stimulating immunoglobulins (4). Therefore, TSHR has become a favorite candidate autoantigen shared between the thyroid gland and the orbital/ dermal connective tissue (3,5).

III. EXPRESSION OF TSH RECEPTORS BY ORBITAL PREADIPOCYTE FIBROBLASTS TSHR is a member of the family of G-protein-coupled receptors with seven transmembrane domains (6,7). Its large extracellular domain serves as a target for thyrotropin, TSHR antibodies (TSAb, TBII), and immune effector cells, and therefore plays a central role in TSHR function and immune recognition (8,9). TSHR has long been considered a thyroidspecific protein, and expression of TSHR in nonthyroidal tissues has been the subject of controversy (10). However, the hypothesis that extrathyroidal adipose cells might express TSHR was forwarded by Rodbell, who demonstrated TSH-stimulated lipolysis in rat epididymal fat cells (11). In addition, TSH binding, TSH-mediated adenylate cyclase activity, TSH-induced lipolysis, and the presence of TSHR mRNA in guinea pig adipose and retroorbital tissues have been reported (12). Results from studies using human cells and tissues have generated more controversial results, with some investigators failing to demonstrate TSH binding to extrathyroidal tissues (13), whereas others have obtained evidence of low- or high-affinity binding to human adipocyte membranes (14,15). Using a variety of techniques (Northern blot analysis, ribonuclease protection assay, reverse transcriptase polymerase chain reaction (RT-PCR), in situ hybridization, immunoblotting, immunohistochemical staining, TSH binding assays), several groups of investigators have detected TSHR mRNA and protein expression in various extrathyroidal tissues, cultured cells and membrane preparations (16–23). A series of elegant experiments has recently demonstrated expression of TSHR in rat brain and in human astrocytes (24). TSHR protein expression has been detected in human neonatal adipocytes, where it declines rapidly with advancing age and becomes undetectable in adult adipocytes (25). The lipolytic effects of TSH are more evident in brown adipose tissue, which may explain why TSH-induced lipolysis in humans is detectable in neonates but is virtually absent during the prepubertal years. Recent reports have shown TSH-induced stimulation of TSHR expression in latepassage cultures of orbital preadipocyte fibroblasts (26). These results suggest that a humoral factor, present in certain patients with GD, might stimulate TSHR expression in orbital cells, which then can act as an orbital autoantigen in GO (27–31). Using a mono-

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clonal TSHR antibody generated by genetic immunization (32), TSHR expression in muscle biopsies and adipose tissue from patients with GO has been compared to that in muscle biopsies obtained from patients undergoing strabismus corrections, in normal orbital fat, and in orbital pseudotumor. In patients with GO, immunostaining was noted on elongated fibroblast-like cells, frequently located adjacent to clusters of adipocytes. No such staining was present in the strabismus or pseudotumor samples, implying that preadipocytes and mature adipocytes express the TSHR in GO. Moreover, using immunocytochemical staining with monoclonal antibodies to the TSHR, TSHR-like immunoreactivity has been demonstrated in orbital preadipocyte fibroblasts in culture and in GO adipose tissue specimens (32). In addition, it was demonstrated that TSHR-like immunoreactivity is detected in frozen sections of orbital tissue specimens obtained from three patients with GO, and to a lesser extent in two samples of normal orbital fat. In vitro, 1–5% of preadipocytes displayed TSHR immunoreactivity in five of six GO samples, in two of three normal orbital tissue samples, and in three of five nonorbital samples. Differentiation was induced in all 14 orbital samples examined, whereas three of four nonorbital samples contained occasional differentiated cells. Of note, 50–70% of differentiating cells demonstrated TSHR-like immunoreactivity. Furthermore, a TSH-mediated increase in cAMP was detected in GO orbital preadipocytes, in GO orbital mature adipocytes, and in nonorbital preadipocytes and mature adipocytes (32). IV.

FUNCTIONALITY OF TSH RECEPTORS IN ORBITAL PREADIPOCYTE FIBROBLASTS

The capacity of the extrathyroidal TSHR to transmit signals and thereby alter certain metabolic and immunological activities in target cells has been examined by several investigators. Earlier studies suggested that TSH and affinity-purified immunoglobulins with high TSHR-stimulating activity indeed alter, in a dose-dependent manner, certain metabolic (e.g., adenylate cyclase activity) and immunological functions (e.g., expression of human leukocyte antigen HLA-DR and ICAM-1) in nonthyroidal cells such as orbital fibroblasts and in transfected, TSHR-expressing CHO cells (31,33,34). Moreover, evidence has been presented suggesting that functional TSHRs are expressed by mature adipocytes,and induced upon preadipocyte differentiation (Fig. 1) (33,34). However, the hormones and cytokines responsible have yet to be characterized. Recently, Valyasevi and colleagues demonstrated that several proinflammatory cytokines such as IFN-γ and TNFα act to inhibit the differentation of orbital preadipocytes, and that IFN-γ, TNF-α, and TGF-β suppress TSHR expression and TSH-dependent cAMP production in orbital preadipocyte fibroblasts (35). Expression of functional TSHR in human preadipocytes and orbital fibroblasts is supported by a recent study by Bell and colleagues (36). Here, TSHR mRNA was detected in human abdominal adipose tissue by Northern blot analysis. Furthermore, TSHR protein was detected, by immunoblotting with two different TSHR autoantibodies, in preadipocytes isolated from human abdominal subcutaneous and omental adipose tissue and in derivative adipocytes differentiated in primary culture. Preadipocytes treated with TSH exhibited a sevenfold increase in the activity of the serine/threonine kinase p70 S6, a recently recognized downstream target of the TSHR in thyrocytes. Activation of p70 S6 kinase by TSH was also observed in orbital fibroblasts, indicating that TSHR expression is present in fibroblasts from various anatomical locations. These observations convincingly demonstrate the presence of functional TSHRs in preadipocyte fibroblasts and suggest that TSHR signaling may be involved in orbital and general

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Figure 1 Proposed roles of the orbital fibroblasts in the pathogenesis of Graves’ ophthalmopathy. TcR, T-cell receptor; VLA-4, very late antigen-4; LFA-1, leukocyte function-associated antigen-1; ICAM-1, intercellular adhesion molecule-1; VCAM-1, vascular cell adhesion molecule-1; Hsp 72, heat shock protein 72; RANTES, regulated on activation, normal T-cell-expressed and secreted; MCP-1, monocyte chemotactic protein-1; MIP-1, macrophage inflammatory protein-1; PDGF, platelet-derived growth factor; TGF-β, transforming growth factor-β; IGF-1, insulin-like growth factor-1; IFN-γ, interferon-γ; TNF-α, tumor necrosis factor-α; MMP-1, matrix metalloproteinase-1; TIMP-1, tissue inhibitor of metalloproteinase-1; PAI-1, plasminogen activator inhibitor-1; GAGs, glycosaminoglycans; PPAR-γ, peroxisome proliferator-activated receptor-γ; PGI2, prostaglandin I2 TSAb, thyroid-stimulating antibodies.

adipogenesis. However, they also indicate that factors other than site-limited TSHR expression are likely to be involved in restricting the distribution of the extrathyroidal manifestations in GD. While there is little doubt that the extrathyroidal TSHR is functional, this capacity must be clearly differentiated from its potential role to serve as an autoantigen. Although recognition of multiple epitopes of the TSHR extracellular domain by antigen-specific T cells has been demonstrated (35,36), it has not been specifically addressed whether autoreactive lymphocytes obtained from affected tissues recognize extrathyroidal TSH receptors following processing by local antigen-presenting cells. In addition, doubts have been raised as to whether the low levels of TSHR transcripts detected in extrathyroidal tissues may be biologically relevant and sufficient to trigger an immune response. However, since large amounts of TSHR protein are present within the thyroid gland that


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can generate large numbers of antigen-specific T cells, even small quantities of TSHR protein in extrathyroidal sites would be sufficient to serve this purpose. Once the autoimmune process is established, circulating sensitized T cells and antibodies could recognize even small quantities of a similar protein at remote sites. Consistent with this concept, several animal models of GD and GO, generated by transfer of TSHR-primed T cells onto BALBc mice, and by genetic immunization with TSHR DNA, have highlighted an important role for the TSHR in their pathogenesis (27–31). Taken together, there is now a significant body of evidence from several laboratories indicating that functional TSHR are expressed by preadipocytes along their differentation pathway towards mature adipocytes. Because orbital fat and fat in other anatomical areas appear to express the TSHR, local factors such as the intraorbital cytokine and hormone milieu, intraorbital pressure, tissue hypoxia, and oxygen free radical damage may promote the clinical expression of GO. In view of these considerations, combining immunomodulatory drugs with agents capable of inhibiting orbital adipogenesis and promoting intraorbital lipopytic activities may be a promising approach in the treatment of patients with active thyroid-associated ophthalmopathy. ACKNOWLEDGMENTS This work has been supported by grants from Deutsche Forschungsgemeinschaft, Bonn, Germany (He 1485/3-1 and He 1485/5-2 and 5-3, Gerhard-Hess-Program). REFERENCES 1. Bahn RS, Heufelder AE. Mechanisms of disease: pathogenesis of Graves’ ophthalmopathy. N Engl J Med 1993; 329:1468–1475. 2. Gorman CA, Heufelder AE, Bartley GB. Ophthalmopathy. In: DeGroot LJ, ed. Endocrinology. Philadelphia: Saunders, 1994:712–715. 3. Heufelder AE. Retro-orbital autoimmunity. Bailliere’s Clin Endocrinol Metab 1997; 11:499– 520. 4. Morris J, Hay ID, Nelson RE, Jiang Nai S. Clinical utility of thyrotropin receptor antibody assays: comparison of radioreceptor and bioassay methods. Mayo Clin Proc 1988; 63:707– 712. 5. Burch HB, Wartofsky L. Graves’ ophthalmopathy: current concepts regarding pathogenesis and management. Endocr Rev 1993; 14:747–793. 6. Nagayama Y, Kaufman KD, Seto P, Rapoport B. Molecular cloning, sequence and functional expression of the cDNA for the human thyrotropin receptor. Biochem Biophys Res Commun 1989; 165:1184–1190. 7. Parmentier M, Libert F, Maenhaut C, Lefort A, Gerard C, Perret J, Van Sande J, Dumont JE, Vassart G. Molecular cloning of the thyrotropin receptor. Science 1989; 246:1620–1622. 8. Murakami M, Mori M. Identification of immunogenic regions in human thyrotropin receptor for immunoglobulin G of patients with Graves’ disease. Biochem Biophys Res Commun 1990; 171:512–518. 9. Kosugi S, Akamizu T, Takai O, Prabhakar BS, Kohn LD. The extracellular domain of the TSH receptor has an immunogenic epitope reactive with Graves’ IgG but unrelated to receptor function as well as determinants having different roles for high affinity TSH binding and the activity of thyroid-stimulating autoantibodies. Thyroid 1991; 1:321–330. 10. Paschke R, Vassart G, Ludgate M. Current evidence for and against the TSH receptor being the common antigen in Graves’ disease and thyroid-associated ophthalmopathy. Clin Endocrinol 1995; 42:565–569.

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11. Rodbell M. Metabolism of isolated fat cells. I. Effects of hormones on glucose metabolism and lipolysis. J Biol Chem 1964; 239:375–380. 12. Roselli-Rehfuss L, Robbins LS, Cone RD. Thyrotropin receptor messenger ribonucleic acid is expressed in most brown and white adipose tissues in the guinea pig. Endocrinology 1992; 130:1857–1861. 13. Davies TF, Teng CS, McLachlan SM, Rees Smith B, Hall R. Thyrotropin receptors in adipose tissue, retro-orbital tissue and lymphocytes. Mol Cell Endocrinol 1978; 9:303–310. 14. Perros P, Kendall-Taylor P. Demonstration of thyrotropin binding sites in orbital connective tissue: possible role in the pathogenesis of thyroid associated ophthalmopathy. J Endocrinol Invest 1994; 17:163–170. 15. Mullin BR, Lee G, Ledley F, Winand R, Kohn L. Thyrotropin interactions with human fat cell membrane preparations and the finding of a soluble thyrotropin binding component. Biochem Biophys Res Commun 1976; 69:55–62. 16. Feliciello A, Porcellini A, Ciullo I, Bonavolonta G, Avvedimento EV, Fenzi G. Expression of thyrotropin-receptor mRNA in healthy and Graves’ retro-orbital tissue. Lancet 1993; 342: 337–338. 17. Endo T, Ohno M, Kotani S, Gunji K, Onaya T. Thyrotropin receptor in non-thyroid tissues. Biochem Biophys Res Commun 1993; 190:774–779. 18. Heufelder AE, Dutton CM, Sarkar G, Donovan KA, Bahn RS. Detection of TSH receptor RNA in cultured fibroblasts from patients with Graves’ ophthalmopathy and pretibial dermopathy. Thyroid 1993; 3:297–300. 19. Crisp MS, Lane C, Halliwell M, Wynford-Thomas D, Ludgate M. Thyrotropin receptor transcripts in human adipose tissue. J Clin Endocrinol Metab 1997; 82:2003–2005. 20. Hiromatsu Y, Sato M, Inoue Y, Koga M, Miyake I, Kameo J, Tokisawa S, Yang D, Nonaka K. Localization and clinical significance of thyrotropin receptor mRNA expression in orbital fat and eye muscle tissues from patients with thyroid-associated ophthalmopathy. Thyroid 1997; 6:553–562. 21. Spitzweg C, Joba W, Hunt N, Heufelder AE. Analysis of human thyrotropin receptor gene expression and immunoreactivity in human orbital tissue. Eur J Endocrinol 1997; 136:599– 607. 22. Stadlmayr W, Spitzweg C, Bichlmair AM, Heufelder AE. Full length TSH receptor transcripts and TSH receptor-like immunoreactivity in orbital and pretibial fibroblasts of patients with Graves’ ophthalmopathy and pretibial dermopathy. Thyroid 1997; 7:3–12. 23. Bahn RS, Dutton CM, Natt N, Joba W, Spitzweg C, Heufelder AE. Thyrotropin receptor expression in Graves’ orbital adipose/connective tissues: potential autoantigen in Graves’ ophthalmopathy. J Clin Endocrinol Metab 1998; 83:998–1002. 24. Crisanti P, Omri B, Hughes EJ, Meduri G, Hery C, Clauser E, Jacquemin C, Saunier B. The expression of thyrotropin receptor in the brain. Endocrinology 2001; 142:812–822. 25. Marcus C, Ehren H, Bolme P, Arner P. Regulation of lipolysis during the neonatal period: Importance of thyrotropin. J Clin Invest 1988; 82:1793–1797. 26. Bahn RS, Dutton CM, Joba W, Heufelder AE. Thyrotropin receptor expression in cultured Graves’ orbital preadipocyte fibroblasts is stimulated by thyrotropin. Thyroid 1998; 8:193– 196. 27. Costagliola S, Many M-C, Stalmans-Falys M, Tonacchera M, Vassart G, Ludgate M. Recombinant TSHR and the induction of autoimmune disease in BALBc mice, a new animal model. Endocrinology 1994; 135:2150–2159. 28. Costagliola S, Many M-C, Stalmans-Falys M, Vassart G, Ludgate M. The autoimmune response induced by immunizing female mice with the human TSHR varies with the genetic background. Mol Cell Endocrinol 1995; 115:119–206. 29. Costagliola S, Many M-C, Stalmans-Falys M, Vassart G, Ludgate M. Transfer of thyroiditis, with syngeneic spleen cells sensitized with the human thyrotropin receptor, to naive balb/c and NOD mice. Endocrinology 1996; 137:4637–4643.


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30. Costagliola S, Rodien P, Many M-C, Ludgate M, Vassart G. Genetic immunization against the human thyrotropin receptor causes thyroiditis and allows production of monoclonal antibodies recognizing the native receptor. J Immunol 1998; 160:1458–1465. 31. Ludgate M. Animal models of Graves’ disease. Eur J Endocrinol 2000; 142:1–8. 32. Crisp M, Starkey KJ, Lane C, Ham J, Ludgate M. Adipogenesis in thyroid eye disease. Invest Ophthalmol Vis Sci 2000; 41:3249–3255. 33. Valyasevi RW, Erickson DZ, Harteneck DA, Dutton CM, Heufelder AE, Jyonouchi SC, Bahn RS. Differentiation of human orbital preadipocyte fibroblasts induces expression of functional thyrotropin receptor. J Clin Endocrinol Metab 1999; 84:2557–2562. 34. Wu SL, Yang CS, Wang HJ, Liao CL, Chang TJ, Chang TC. Demonstration of thyrotropin receptor mRNA in orbital fat and eye muscle tissues from patients with Graves’ ophthalmopathy by in situ hybridization. J Endocrinol Invest 1999; 22:289–295. 35. Valyasevi RW, Jyonouchi SC, Dutton CM, Munsakul N, Bahn RS. Effect of tumor necrosis factor-alpha, interferon-gamma, and transforming growth factor-beta on adipogenesis and expression of thyrotropin receptor in human orbital preadipocyte fibroblasts. J Clin Endocrinol Metab 2001; 86:903–908. 36. Bell A, Gagnon A, Grunder L, Parikh SJ, Smith TJ, Sorisky A. Functional TSH receptor in human abdominal preadipocytes and orbital fibroblasts. Am J Physiol Cell Physiol 2000; 279: C335–C340. 37. Heufelder AE. Involvement of the orbital fibroblast and TSH receptor in the pathogenesis of Graves’ ophthalmopathy. Thyroid 1995; 5:331–340. 38. Heufelder AE, Bahn RS. Evidence for the presence of a functional TSH receptor in retroocular fibroblasts from patients with Graves’ ophthalmopathy. Exp Clin Endocrinol Diabetol 1992; 100:62–67. 39. Arnold K, Tandon N, McIntosh RS, Elisei R, Ludgate M, Weetman AP. T cell responses to orbital antigens in thyroid-associated ophthalmopathy. Clin Exp Immunol 1994; 96:329–334. 40. Akamizu T, Ueda Y, Hua L, Okuda J, Mori T. Establishment and characterization of an antihuman thyrotropin (TSH) receptor-specific CD4⫹ T cell line from a patient with Graves’ disease: evidence for multiple T cell epitopes on the TSH receptor including the transmembrane domain. Thyroid 1995; 5:259–264.

22 Role of Orbital Fat in ThyroidAssociated Ophthalmopathy TERRY J. SMITH Harbor–UCLA Medical Center, Torrance, and UCLA School of Medicine, Los Angeles, California, U.S.A.

I.

INTRODUCTION

Connective tissue investing the human orbit appears to be particularly susceptible to the factors directly responsible for the pathogenesis of Graves’ disease. The orbital disease, termed thyroid-associated ophthalmopathy (TAO), involves the extensive remodeling of connective tissue (1). While the proximate connection between the glandular disease and TAO remains unknown, trafficking of activated T lymphocytes to the thyroid gland and orbit represents a prominent feature of both. Why the connective/adipose tissue of the orbit should be singled out for disease targeting is uncertain but intrinsic differences in the resident cells might underlie this susceptibility. Another open question relates to the variations in clinical presentations among patients with TAO. Some manifest predominantly eye muscle enlargement while others exhibit disease limited to the fat/connective tissue depot behind the eye. The basis for this differential presentation could be related to distinct populations of fibroblasts inhabiting the extraocular muscles and adipose/connective tissue compartments. A topic of considerable interest has been the identification of an autoantigen exhibiting a pattern of expression limited to the orbit, thyroid, and the lower leg. These three sites manifest Graves’ disease most frequently (1). The thyrotropin receptor (TSHR) remains the likely candidate autoantigen, largely because of its well-established role in the pathogenesis of thyroid growth and hyperactivity associated with Graves’ disease. Just how it participates in orbital and dermal components of the disease remains to be elucidated. As will be discussed, the TSHR is expressed far more widely than was thought initially. Several tissues have been examined and found to express TSHR mRNA and/or protein. 215

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II. ORBITAL FIBROBLAST SUSCEPTIBILITY TO PROINFLAMMATORY CYTOKINES An important question concerning the remodeling associated with TAO is whether orbital connective tissues exhibit peculiar properties that underlie their vulnerability to disease. The predominant resident cell type in this tissue is the fibroblast. Orbital fibroblasts possess a phenotype, when cultured, that sets them apart from other fibroblasts. They have a distinct morphology and respond differently to thyroid hormone and glucocorticoids than do extraorbital fibroblasts (2). They display different profiles of surface receptors (3) and gangliosides (4). Cytokines enhance the generation of hyaluronan, a nonsulfated glycosaminoglycan, in orbital fibroblasts and the magnitude of this effect is considerably greater than that observed in other fibroblasts (5,6). This is the case for cultures derived from normal and TAO tissue. Interferon-γ upregulates hyaluronan accumulation in orbital fibroblasts but not in cultures from the skin (5). Leukoregulin, a proinflammatory product of activated T lymphocytes, and CD40 ligand, also known as CD154, induce hyaluronan production robustly in orbital fibroblasts (6,7). Moreover, interleukin (IL)-1β and other proinflammatory cytokines induce members of the hyaluronan synthase family (8) and the UDP-glucose dehydrogenase gene (9) in orbital fibroblasts. All three members of the HAS family are induced in orbital fibroblasts, but HAS2 mRNA is the most abundant isoform transcript detected under cytokine-activated culture conditions (8). These findings suggest that multiple enzymatic components of the hyaluronan biosynthetic pathway are regulated in these cells. Why multiple HAS enzymes might be expressed in orbital fibroblasts is unclear. However, the expression of several isoforms may be related to their potentially different roles in tissue function. Glucocorticoids can block partially the effects of cytokines on hyaluronan synthesis in orbital fibroblasts. These inhibitory actions are mediated through downregulation of enzyme mRNA expression (8,9). When profiles of expression in orbital and nonorbital fibroblasts are compared using two-dimensional electrophoresis, several individual proteins appear to be differentially regulated by proinflammatory cytokines (10,11). Among these, plasminogen activator inhibitor type-1, a 47 kDa glycoprotein serine protease inhibitor, is induced dramatically in orbital fibroblasts (10,12). This protein inhibits plasmin-mediated extracellular matrix proteolysis. The high level of expression in orbital fibroblasts following cytokine activation could result in a stabilized extracellular matrix and thus allow the accumulation of a number of molecules, the disposal of which would be retarded. Prostaglandin endoperoxide H synthase 2 (PGHS-2), the inflammatory cyclooxygenase, was found to be upregulated to extraordinary levels by cytokines such as IL-1β and leukoregulin in orbital cultures (13,14). A result of the induction of PGHS-2 is the greatly enhanced production of prostaglandin E2 (PGE2). It would appear that the exaggerated induction of PGHS-2 in orbital cultures might represent, at least in part, the molecular basis for the intense inflammation seen in the diseased orbit. Thus, the inhibition of PGHS-2 with nonsteroidal antiinflammatory drugs could represent an important and largely overlooked therapeutic strategy in patients manifesting active orbital inflammation.

III. ORBITAL FIBROBLAST EXPRESSION OF CD40 An important clue to the reactivity demonstrated by orbital connective tissues relates to the expression of CD40 by orbital fibroblasts (7,15). Cells derived from other tissues involved in autoimmune inflammation also express this receptor, including lung, gingival,

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and synovial fibroblasts. CD40, first recognized in B lymphocytes, is a member of the tumor necrosis factor (TNF)-α receptor family. When ligated by CD154, CD40 mediates B cell activation. CD154, a member of the TNF-α family, is expressed by T lymphocytes and the CD40/CD154 bridge is thought to represent an important activational conduit between these two lymphocyte types. Expression of CD154 has been recognized on a wide array of cells other than T lymphocytes and the CD40/CD154 bridge may well represent a widespread molecular platform for cell-to-cell interactions. In fact, mast cells and platelets also express particularly high levels of CD154. Moreover, some of the cell types expressing functional CD40 may also display CD154, suggesting a potential shortloop pathway involved in autocrine regulation. When orbital fibroblasts are treated with recombinant CD154, a number of proinflammatory genes are activated. These include IL-1α, IL-6, IL-8, and PGHS-2 (7,15). The induction of PGHS-2 results in a dramatic increase in the synthesis of PGE2. In addition, the production of hyaluronan in orbital fibroblasts is enhanced by CD40 ligation (7). Thus the CD40/CD154 bridge is potentially important for activating orbital fibroblasts through a direct interaction with activated T lymphocytes and mast cells. Moreover, several aspects of the fibroblast phenotype that would be involved in the tissue remodeling observed in TAO can be attributed to the known consequences of the CD40/CD154 activation. IV.

ORBITAL CONNECTIVE TISSUE FIBROBLAST SUBPOPULATIONS

Orbital fibroblasts derived from the adipose/connective tissue depot and cultivated in culture contain subpopulations of cells with distinct phenotypes. For instance, cells can be separated on the basis of the display of Thy-1, a surface glycoprotein (16). Approximately 50% of orbital fibroblasts, whether harvested from normal orbital connective tissue or from patients with TAO, express Thy-1 (17). This fraction remains relatively constant with prolonged culture over many population doublings (17). The Thy-1 is displayed on the surfaces of fibroblasts and may be competent to signal downstream targets. While the physiological significance of Thy-1 expression is uncertain, specific phenotypic attributes appear to cosegregate with its display. In murine lung fibroblasts, Thy-1-expressing cells utilize members of the IL-1 family of cytokines differently than do those without the determinant (18). Human leukocyte antigen (HLA)-DR class II molecule expression following priming with interferon-γ also differs (18). Thus there is reason to anticipate substantial variation in cell signaling in the two orbital fibroblast populations. Indeed, preliminary results suggest marked differences in proinflammatory cytokine production between the activated orbital fibroblast subsets. V. ORBITAL FIBROBLAST CELLS CAN UNDERGO ADIPOCYTE DIFFERENTIATION It would appear that a subpopulation of orbital cells undergoes adipogenic differentiation when they are incubated in culture medium supplemented with insulin, dexamethasone, prostaglandin I2 (PGI2), T3, and isobutylmethylxanthone (19). This transition occurs over the course of many days and culminates with cells accumulating droplets of triglyceride in their cytoplasm (19). The fraction of cells undergoing adipogenic change that could be discerned at the light microscopic level of detection was approximately 10% under the above described culture conditions (19). Because of the relatively small proportion of cells differentiating, the culture conditions have been modified subsequently to include

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the PPAR-γ ligand, rosiglitazone. Addition of this compound has yielded a consistently greater degree of differentiation and nearly 50% of the cells can undergo transition to mature adipocytes. When these mature adipocytes were stained subsequently for Thy-1 expression, the glycoprotein was undetectable, suggesting that those fibroblasts not displaying Thy-1 may represent a pool of preadipocytes. The implication of an adipogenic potential exhibited by orbital fibroblasts is substantial. It suggests that one mechanism for the increase in volume of orbital contents in TAO could relate to an expansion in the fat mass. Thus the tissue swelling may not be fully attributable to the accumulation of hyaluronan. It is possible that the number/size of the resident adipocytes in this disease increases from that found in healthy orbital tissue. Mature orbital adipocytes might express profiles of genes relevant to the pathogenesis of TAO that differ from those found in undifferentiated fibroblasts. In particular, expression of a pathogenic autoantigen might result as a consequence of fibroblast differentiation. With regard to clinical presentation, appreciating the capacity of orbital fibroblasts to undergo adipogenesis could explain the apparent fatty infiltration of extraocular muscle in TAO. This phenomenon has been documented with magnetic resonance imaging (MRI) and computed tomography (CT) (20). It is possible that the complex structure of the orbital fat could demarcate subpopulations of fibroblasts, each with a distinct adipogenic potential. Loss of this potential with aging could account for the more pronounced expansion of fat observed in children than in adults with TAO. These and other possibilities will need to be explored in future studies directed at more fully assessing the pattern of cellular differentiation of orbital preadipocytes. VI.

ORBITAL FIBROBLASTS EXPRESS THE TSH RECEPTOR

A great deal of excitement surrounded the cloning and molecular characterization of the TSHR. Soon after the initial reports, studies appeared demonstrating TSHR mRNA in orbital connective tissue from patients with Graves’ disease and from normal orbital contents (21). These were followed by similar observations in cultured orbital fibroblasts where the transcript could be detected (22). Early studies relied on mRNA detection utilizing reverse transcriptase–polymerase chain reaction (RT-PCR) and thus concerns were raised relating to the reliability of such measurements. Subsequently, studies involving in situ hybridization, nuclease protection, and northern hybridization documented the presence of the transcript, and western blot analysis of TSHR protein has confirmed expression in several extraorbital connective/adipose tissue depots and in cells derived from those tissues (23–27). A premise put forward by some investigators concerns the concept that the TSHR is expressed only in the tissues manifesting Graves’ disease, notably the orbit and skin of the lower leg. An early study demonstrated a truncated variant of the TSHR mRNA expressed in non-thyroidal tissue including fibroblasts from eye muscle (28). The authors concluded that the receptor was not functional since addition of recombinant TSH to the cultures failed to alter glycosaminoglycan production or cAMP generation (28). Full-length TSHR mRNA has been found subsequently in extra thyroidal tissues. TSHR mRNA was detected using northern analysis in the abdominal fat of infants and lower levels of the transcript were found in fat from adult donors (29). More recently, TSHR protein and/or mRNA was found to be expressed in fibroblasts from other connective tissues including preadipocytes harvested from the abdominal wall and from the omentum (27). Reports containing functional studies have largely focused on TSH eliciting increases in cAMP levels in preadipocytes/adipocytes. These data have been unconvincing largely

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because the magnitude of the effects has been small and the results appear inconsistent. TSH has been shown to stimulate mitogenesis in a rat thyrocyte cell line and this effect has been linked to the activation of the p70S6K pathway (30). This is noteworthy because of the recent finding that the TSHR in preadipocytes/fibroblasts might also signal through the p70S6K (27). It is thus possible that the signaling pathways utilized by the ligated TSHR may vary with the cell type. One recent study found increased TSHR expression following orbital fibroblast differentiation and this was coupled with an enhanced production of cAMP provoked by TSH (31). The authors claimed a 20% differentiation rate, which is inconsistent with the photomicrograph provided as evidence. Moreover, the large fractional increase in cellular response to TSH attributed to differentiation in 20% of the cells is surprising. A far more likely possibility, and one that was apparently not controlled for, relates to the impact certain cAMP-enhancing components of the medium might have exerted on the cells. These effects would not necessarily be related to adipogenic differentiation. A second such report, from a different laboratory, has also suggested that an increase in TSHR activity may accompany fibroblast differentiation (32). Further studies will be necessary to define more fully the pattern of TSHR expression in extrathyroidal tissues and to identify physiological roles for the receptor in cells of the fibroblast lineage. VII.

CONCLUSIONS

The adipose/connective tissue depot in the human orbit is susceptible to inflammation such as occurs in TAO. Why this tissue is singled out for involvement in this disease is uncertain. Preadipocytes/fibroblasts from the orbit exhibit a phenotype in culture that sets them apart from fibroblasts derived from other anatomical sites. They can differentiate into mature adipocytes and respond excessively to proinflammatory cytokines and other disease mediators. The proximate link between the orbit and thyroid leading to involvement in Graves’ disease is uncertain. Expression of the TSHR appears to be widespread among cells of the fibroblast lineage. Thus, the suggestion that orbital connective tissue is targeted for disease involvement by virtue of its TSHR expression is probably incorrect. With regard to the orbital fat, expansion of this compartment can result in significant morbidity associated with TAO. Understanding the biological properties of the fibroblasts from this tissue more completely may ultimately help us define the pathogenesis of TAO and other inflammatory diseases of the orbit. ACKNOWLEDGMENTS This work was supported in part by National Institutes of Health Grants EY08976 and EY11708 and by the Merit Review award from the Research Service of the Department of Veterans Affairs. REFERENCES 1. Smith TJ, Bahn RS, Gorman CA. Connective tissue, glycosaminoglycans, and diseases of the thyroid. Endocr Rev 1989; 10:366–391. 2. Smith TJ, Bahn RS, Gorman CA. Hormonal regulation of hyaluronate synthesis in cultured human fibroblasts: evidence for differences between retroocular and dermal fibroblasts. J Clin Endocrinol Metab 1989; 69:1019–1023.

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3. Smith TJ, Kottke RJ, Lum H, Andersen TT. Human orbital fibroblasts in culture bind and respond to endothelin. Am J Physiol 1993; 265:C138–C142. 4. Berenson CS, Smith TJ. Human orbital fibroblasts in culture express ganglioside profiles distinct from those in dermal fibroblasts. J Clin Endocrinol Metab 1995; 80:2668–2674. 5. Smith TJ, Bahn RS, Gorman CA, Cheavens M. Stimulation of glycosaminoglycan accumulation by interferon gamma in cultured human retroocular fibroblasts. J Clin Endocrinol Metab 1991; 72:1169–1171. 6. Smith TJ, Wang H-S, Evans CH. Leukoregulin is a potent inducer of hyaluronan synthesis in cultured human orbital fibroblasts. Am J Physiol 1995; 268:C382–C388. 7. Cao HJ, Wang H-S, Zhang Y, Lin H-Y, Phipps RP, Smith TJ. Activation of human orbital fibroblasts through CD40 engagement results in a dramatic induction of hyaluronan synthesis and prostaglandin endoperoxide H synthase-2 expression. J Biol Chem 1998; 273:29615– 29625. 8. Kaback LA, Smith TJ. Expression of hyaluronan synthase messenger ribonucleic acids and their induction by interleukin-1β in human orbital fibroblasts: potential insight into the molecular pathogenesis of thyroid-associated ophthalmopathy. J Clin Endocrinol Metab 1999; 84: 4079–4084. 9. Spicer AP, Kaback LA, Smith TJ, Seldin MF. Molecular cloning and characterization of the human and mouse UDP-glucose dehydrogenase genes. J Biol Chem 1998; 273:25117–25124. 10. Smith TJ, Ahmed A, Hogg MG, Higgins PJ. Interferon-γ is an inducer of plasminogen activator inhibitor type 1 in human orbital fibroblasts. Am J Physiol 1992; 263:C24–C29. 11. Young DA, Evans CH, Smith TJ. Leukoregulin induction of protein expression in human orbital fibroblasts: evidence for anatomical site-restricted cytokine-target cell interactions. Proc Natl Acad Sci USA 1998; 95:8904–8909. 12. Hogg MG, Evans CH, Smith TJ. Leukoregulin induces plasminogen activator inhibitor type 1 in human orbital fibroblasts. Am J Physiol 1995; 269:C359–C366. 13. Wang H-S, Cao HJ, Winn VD, Rezanka LJ, Frobert Y, Evans CH, Sciaky D, Young DA, Smith TJ. Leukoregulin induction of prostaglandin-endoperoxide H synthase-2 in human orbital fibroblasts: an in vitro model for connective tissue inflammation. J Biol Chem 1996; 271: 22718–22728. 14. Cao HJ, Smith TJ. Leukoregulin upregulation of prostaglandin endoperoxide H synthase-2 expression in human orbital fibroblasts. Am J Physiol 1999; 277:C1075–C1085. 15. Sempowski GD, Rozenblit J, Smith TJ, Phipps RP. Human orbital fibroblasts are activated through CD40 to induce proinflammatory cytokine production. Am J Physiol 1998; 274:C707– C714. 16. Morris RJ, Ritter MA. Association of Thy-1 cell surface differentiation with certain connective tissues in vivo. Cell Tissue Res 1980; 206:459–475. 17. Smith TJ, Sempowski GD, Wang H-S, Del Vecchio PJ, Lippe SD, Phipps RP. Evidence for cellular heterogeneity in primary cultures of human orbital fibroblasts. J Clin Endocrinol Metab 1995; 80:2620–2625. 18. Phipps RP, Baecher C, Frelinger JG, Penney DP, Keng P, Brown D. Differential expression of interleukin 1α by Thy-1⫹ and Thy-1⫺ lung fibroblast subpopulations: enhancement of interleukin 1α production by tumor necrosis factor-α. Eur J Immunol 1990; 20:1723–1727. 19. Sorisky A, Pardasani D, Gagnon A, Smith TJ. Evidence of adipocyte differentiation in human orbital fibroblasts in primary culture. J Clin Endocrinol Metab 1996; 81:3428–3431. 20. Kemp EG, Rootman J. Lipid deposition within the extra-ocular muscles of a patient with dysthyroid ophthalmopathy. Orbit 1989; 8:45–48. 21. Feliciello A, Porcellini A, Ciullo I, Bonavolota` G, Avvedimento E, Fenzi G. Expression of thyrotropin-receptor mRNA in healthy and Graves’ disease retroorbital tissue. Lancet 1993; 342:337–338. 22. Heufelder AE, Dutton CM, Sarkar G, Donovan KA, Bahn RS. Detection of TSH receptor RNA

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in cultured fibroblasts from patients with Graves’ ophthalmopathy and pretibial dermopathy. Thyroid 1993; 3:297–300. Wu S-L, Yang C-SJ, Wang H-J, Liao C-L, Chang T-J, Chang T-C. Demonstration of thyrotropin receptor mRNA in orbital fat and eye muscle tissues from patients with Graves’ ophthalmopathy by in situ hybridization. J Endocrinol Invest 1999; 22:289–295. Crisp MS, Lane C, Halliwell M, Wynford-Thomas D, Ludgate M. Thyrotropin receptor transcripts in human adipose tissue. J Clin Endocrinol Metab 1997; 82:2003–2005. Spitzweg C, Joba W, Hunt N, Heufelder AE. Analysis of human thyrotropin receptor gene expression and immunoreactivity in human orbital tissue. Eur J Endocrinol 1997; 136:599– 607. Burch HB, Sellitti D, Barnes SG, Nagy EV, Bahn RS, Burman KD. Thyrotropin receptor antisera for the detection of immunoreactive protein species in retroocular fibroblasts obtained from patients with Graves’ ophthalmopathy. J Clin Endocrinol Metab 1994; 78:1384–1391. Bell A, Gagnon A, Grunder L, Parikh SJ, Smith TJ, Sorisky A. Functional TSH receptor in human abdominal preadipocytes and orbital fibroblasts. Am J Physiol 2000; 279:C335–C340. Paschke R, Metcalfe A, Alcalde L, Vassart G, Weetman A, and Ludgate M. Presence of nonfunctional thyrotropin receptor variant transcripts in retroocular and other tissues. J Clin Endocrinol Metab 1994; 79:1234–1238. Janson A, Rawet H, Perbeck L, Marcus C. Presence of thyrotropin receptor in infant adipocytes Pediatr Res 1998; 43:555–558. Cass LA, Meinkoth JL. Differential effects of cyclic adenosine 3′, 5′-monophosphate on p70 ribosomal S6 kinase. Endocrinology 1998; 139:1991–1998. Valyasevi RW, Erickson DZ, Harteneck DA, Dutton CM, Heufelder AE, Jyonouchi SC, Bahn RS. Differentiation of human orbital preadipocyte fibroblasts induces expression of functional thyrotropin receptor. J Clin Endocrinol Metab 1999; 84:2257–2262. Crisp M, Starkey KJ, Lane C, Ham J, Ludgate M. Adipogenesis in thyroid eye disease. Invest Ophthalmol Vis Sci 2000; 41:3249–3255.

23 Eye Muscle Autoantibodies in Graves’ Orbital Disease MASAYO YAMADA Yamanashi University, Yamanashi, Japan AUDREY WU LI, CHENG-HSIEN CHANG, and JACK R. WALL Dalhousie University, Halifax, Nova Scotia, Canada

I.

INTRODUCTION

The exophthalmos and visual damage seen in some patients with Graves’ hyperthyroidism are well-known extrathyroidal manifestations of that disease (1–3). Acropachy and pretibial myxedema, or dermopathy, are also components of what is known as Graves’ disease. Exophthalmos, or proptosis, occurs because of swelling of the orbital contents, in particular the extraocular muscles and the surrounding orbital connective tissue. Graves’ orbital disease, or ophthalmopathy, occurs in 25–50% of patients with Graves’ hyperthyroidism, occasionally in patients with Hashimoto’s thyroiditis, and rarely in those with no evident thyroid disease (4,5). In this chapter we use the term thyroid-associated ophthalmopathy (TAO) to indicate ophthalmopathy associated with Graves’ hyperthyroidism or Hashimoto’s thyroiditis. The eye changes of Graves’ disease can be classified as infiltrative or noninfiltrative (6). Features of infiltrative ophthalmopathy include edema of the lids, periorbital tissues, and conjunctiva; conjunctival injection and eye pain; irritation; and a sensation of grittiness. These features comprise what has been called the congestive ophthalmopathy subtype of TAO (7). The extraocular muscles may be infiltrated, inflamed, and enlarged, affecting the eye’s ability to move and resulting in diplopia and sometimes a complete loss of oculomotor activity. These latter changes comprise the ocular myopathy subtype of TAO. In other patients both types occur in mixed disease. TAO is a progressive eye disorder in which there is good evidence for immunemediated inflammation of the extraocular muscles and orbital connective tissue (6). The nature of the initial events leading to orbital disease in patients with thyroid autoimmunity 223

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and the identity of the target antigens are still poorly understood and hotly debated. It is now known that serum antibodies against 55 kDa and 64 kDa eye muscle membrane proteins are important markers of eye muscle damage in patients with thyroid autoimmunity. These proteins have recently been sequenced and characterized, and new information using an experimental model for TAO (8) is expected to lead to a better understanding of the causes of this common orbital disorder. Studies aimed at elucidating the pathogenesis of the eye muscle component of Graves’ orbital disease are summarized in this chapter. Although TAO is generally considered to have an autoimmune cause, the identity and nature of the principal target antigens, the mechanism for the close association of ophthalmopathy with thyroid autoimmunity, and the basis for the localization of a muscle reaction in the orbit are unclear (9,10). The notion of TAO subtypes is consistent with the two main hypotheses for the pathogenesis of ophthalmopathy. Some workers believe that the orbital connective tissue and fat are the sites of the primary inflammatory reaction and that eye muscle damage is secondary to this (11,12). No candidate antigens have been conclusively identified in this compartment although the thyrotropin (TSH) receptor (TSHR) is thought by many to be the sought-after thyroid and orbit shared antigen (13,14). We, and others, have postulated a role of eye muscle antigens, in particular those eye muscle membrane proteins of 55 and 64 kDa identified by immunoblotting, and suggest that stimulation of the orbital fibroblasts may be secondary to eye muscle inflammation (15–19). It has been difficult to convincingly demonstrate eye muscle fiber damage in the early stages of TAO. This may reflect the fact that eye muscle tissue from patients with Graves’ hyperthyroidism without eye signs is usually unavailable for examination.

II. ORBITAL HISTOPATHOLOGICAL FINDINGS A.

By Light Microscopy

The most apparent clinical anatomical abnormality in TAO is the enlargement of extraocular muscles, although the orbital fat/connective tissue is also involved. The extraocular muscle fibers themselves usually appear normal, but are widely separated by increased amounts of connective tissue and hydrophilic extracellular matrix compounds (20–24). The initial infiltrate is both focal and diffuse and consists mainly of T lymphocytes. Lymphocytes are also seen in the connective tissue surrounding the extraocular muscle cells and in the fatty tissue (25,26). At a later stage, fibroblasts enlarge and proliferate, and muscle edema, related to increased deposition of glycosaminoglycans by activated fibroblasts, is found (27). Finally, the muscles become fibrotic and atrophy (28,29). B.

By Electron Microscopy

Recent electron microscopic findings in orbital tissue from patients with severe, active TAO have revealed extensive muscle fiber damage ranging from dissolution of the Z bands, abnormalities in the mitochondria, enlargement and displacement of the nuclei and lipid vacuoles, to massive necrosis of the myocytes associated with fibrosis (19). These findings suggest a role for autoimmunity against eye muscle antigens in the expression of TAO. The relative contributions of cytotoxic antibodies and cellular mechanisms for eye muscle fiber destruction are not known. Because of the unavailability of orbital tissues from patients with Graves’ hyperthyroidism showing no evident ophthalmopathy, it has not been possible to document the earliest stages of TAO.

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III. EYE MUSCLE AUTOANTIGENS Serum antibodies against eye muscle antigens of MW 55–95 kDa are detected in about 70% of patients with active ophthalmopathy and eye muscle dysfunction (2,5,30–34), although some others have not found such a close association (35,36). Kubota et al. (37) have recently reported that eye muscle membrane antigens of 63–67 kDa include three proteins: the flavoprotein (Fp) subunit of the mitochondrial enzyme succinate dehydrogenase, the ‘‘64 kDa protein’’ (29,30); a non–tissue-specific membrane protein called 1D (38–40); and the calcium-binding protein calsequestrin, which is localized in the sarcoplasmic reticulum of the skeletal muscle fiber (41). These proteins have small differences in MW and band density on immunoblotting (37). A. 64 kDa Protein Antibodies reactive with the Fp subunit of the mitochondrial enzyme succinate dehydrogenase are most closely associated with progressive ophthalmopathy (30,31,42–46), whereas those reactive with a 55 kDa eye muscle protein may be the first produced in patients with TAO (47). Serum autoantibodies reactive with a 64 kDa protein were detected in 62% of patients with recent onset of TAO, in 33% of those with chronic stable disease, in 39% with Graves’ hyperthyroidism, in 25% of patients with Hashimoto’s thyroiditis, and in 16% of normal subjects (43) (Table 1). When Fp, purified from beef heart succinate dehydrogenase, was used as antigen in Western blotting, the prevalences were 67% in active TAO, 30% in chronic disease of ⬎3 years duration, 30% in Graves’ hyperthyroidism, and 7% of normal subjects (30) (Table 2). Antibodies against Fp were detected in 73% of patients with active TAO; in 5% with more chronic, stable disease; in 14% with

Table 1 Prevalences of Serum Antibodies Against 55 and 64 kDa Eye Muscle Antigens in Patients with Thyroid-Associated Ophthalmopathy, Thyroid Autoimmunity Without Ophthalmopathy, and Control Patients and Subjects, Measured by Western Blotting Positive testsa Group TAO ⬍1 yr TAO ⬎3 yr Graves’ hyperthyroidism Hashimoto’s thyroiditis Normals a

64 kDa protein

55 kDa protein

62% p ⬍ 0.05b 33% NS 39% NS 25% NS 16%

35% p ⬍ 0.01 NT 42% p ⬍ 0.01 17% NS 0%

Taken as a band at stated mol wt by comparison with standards. Statistical analyses refer to differences in prevalences in test groups, compared to control mice, assessed using Fisher’s direct test. A p value of ⬍0.05 is taken as significant. NS, not significant; NT, not tested. Source: From Refs. 43 and 45. b

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Table 2 Prevalences of Serum Antibodies Against Purified Fp and G2s in Patients with ThyroidAssociated Ophthalmopathy, Thyroid Autoimmunity Without Ophthalmopathy, and Control Patients and Subjects, Measured by Western Blotting Positive testsa Group TAO ⬍1 yr TAO ⬎3 yr Graves’ hyperthyroidism Hashimoto’s thyroiditis Normals

Fp

G2s

67% p ⬍ 0.001b 30% NS 30% NS NT

70% p ⬍ 0.001 53% p ⬍ 0.01 36% p ⬍ .01 17% NS 16%

7%

a

Taken as a band at stated mol wt by comparison with standards. Statistical analyses refer to differences in prevalences in test groups, compared to control mice, assessed using Fisher’s direct test. A p value of ⬍0.05 is taken as significant. NS, not significant; NT, not tested. Source: From Refs. 30 and 32. b

Graves’ hyperthyroidism without ophthalmopathy; in 20% of patients with Hashimoto’s thyroiditis; but in only 7% of normal subjects, by enzyme-linked immunosorbent assay (ELISA) (Table 3) (30). In a serial study of over 100 patients with Graves’ hyperthyroidism, serum antibodies against Fp predicted the development of ocular myopathy in five of the six patients in whom this occurred following antithyroid drug treatment. However, it did not predict congestive ophthalmopathy, which also occurred in six patients (31), as summarized in Figure 1. The preparation of Fp that we used in these studies contained, as well as Fp, the flavine adenine dinucleotide (FAD) cofactor. A small proportion of sera from patients with TAO react with FAD, which is covalently bound to succinate dehydrogenase, sarcosine dehydrogenase, and dimethylglycine dehydrogenase. A proportion of so-called false-positive reactions in subjects without ophthalmopathy in our earlier studies can be explained by reaction against FAD (Wall et al., unpublished data). Antibodies against Fp were also found in the great majority of patients with ocular myasthenia gravis and generalized myasthenia gravis, in one study (48), suggesting that these antibodies are secondary to eye muscle damage of an immune nature and not specific to TAO. It is also possible that these antibodies are secondary to cardiac muscle damage (e.g., following myocardial infarction, myocarditis, or nonspecific cardiomyopathy), although this has not yet been studied. B.

55 kDa Protein

Another protein closely associated with TAO is the so-called 55 kDa protein. The 55 kDa eye muscle protein was recently cloned and named G2s (32). G2s is a novel thyroid and eye muscle shared protein. G2s is now identified as the terminal 141 amino acids of the


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Table 3 Prevalences of Serum Antibodies Against Purified Fp and G2s in Patients with Thyroid-Associated Ophthalmopathy, Thyroid Autoimmunity Without Ophthalmopathy, and Control Patients and Subjects, Measured in Enzyme-Linked Immunosorbent Assay Positive testsa Group TAO ⬍1 yr TAO ⬎3 yr Graves’ hyperthyroidism Hashimoto’s thyroiditis Normals

Fp

G2s

73% p ⬍ 0.001b 5% NS 14% NS 20% NS 12%

54% p ⬍ 0.001 33% NS 36% NS 54% p ⬍ 0.001 11%

Taken as OD ⬎ mean ⫹ 2SD for normals. Statistical analyses refer to differences in prevalences in test groups, compared to control mice, assessed using Fisher’s direct test. A p value of ⬍0.05 is taken as significant. NS, not significant. Source: From Refs. 30 and 32. a

b

Figure 1 Serial anti-Fp antibody levels in the 12 out of 101 patients with Graves’ hyperthyroidism who developed ophthalmopathy after treatment with methimazole, studied prospectively. Blood was drawn at approximately 3 monthly intervals after the commencement of treatment of the hyperthyroidism, and serum was tested, by ELISA, for antibodies reactive against flavoprotein. The results are expressed as OD at 410 nM. Serum anti-Fp subunit antibody levels in 6 patients who developed eye muscle disease after treatment of the hypertyroidism (A) and 6 patients who developed congestive ophthalmopathy but no evident eye muscle disease (B), are shown. The hatched horizontal line at 0.200 OD is the upper limit of normal, calculated as mean ⫹2SD for a panel of 10 age- and sex-matched normal subjects tested concurrently. (From Ref. 31.)

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winged-helix transcription factor Foxp1. The prevalence of antibodies targeting the 55 kDa protein was 35% in patients with TAO and 42% in those with Graves’ hyperthyroidism, by Western blotting (Table 1) (45). Antibodies against a G2s fusion protein were detected in 54% of patients with TAO of ⬍1 year duration, 33% of those with stable disease of ⬎3 years duration, 36% with Graves’ hyperthyroidism, 54% with Hashimoto’s thyroiditis, and in 11% of normal subjects, by ELISA (32) (Table 3). By Western blotting, the prevalences were 70% in patients with active TAO, 53% in those with chronic disease, 36% in Graves’ hyperthyroidism, 17% in patients with Hashimoto’s thyroiditis, and 16% in normal subjects (32) (Table 2). Antibodies reactive against the 55 kDa protein were shown to be closely associated with extraocular muscle enlargement as demonstrated by orbital computed tomography (15). In one patient with TAO, serum concentration of antibodies against the 55 kDa protein decreased during treatment of the ophthalmopathy (47), suggesting that this antibody is an early marker of ophthalmopathy. It is most likely that eye muscle damage in ophthalmopathy is mediated by cytotoxic antibodies or CD8⫹ T lymphocytes targeting a cell membrane antigen, such as G2s, and that sensitization to Fp, and some other proteins to be discussed below, is secondary. In a prospective study following antithyroid drug therapy, antibodies against a G2s-fusion protein predicted the development of both congestive ophthalmopathy and ocular myopathy in patients with Graves’ hyperthyroidism. In the same study anti-Fp antibodies were detected only in those patients who developed the ocular myopathy subtype of TAO (31,49). G2s is potentially an important and interesting antigen in TAO because it is strongly expressed in both thyroid and eye muscle, but not in orbital connective tissue (32). Thus it is a good candidate for an eye muscle and thyroid shared antigen that may be the basis for some relationship between ophthalmopathy and thyroid autoimmunity. G2s is also expressed in some other tissues that are not usually the sites of autoimmune attack in Graves’ disease. While not explained, this may reflect the unique characteristics of the eye muscle fiber. Others (10–14,50–52) have shown that the TSHR is expressed in the orbital preadipocyte and postulate that targeting of this protein is the mechanism for the association. One group (53) has demonstrated expression of the receptor protein in ‘‘eye muscle,’’ although the precise cellular site of the protein was not shown in that study. The relationship between G2s and the other eye muscle antigens that have been identified is unknown. The pathogenetic role of anti-G2s antibodies has not been established and they may be secondary to autoimmune attack against another, as yet unidentified, orbital cell membrane antigen. C.

Cytotoxic Antibodies

In earlier studies, we demonstrated the presence of cytotoxic antibodies against cultured normal human eye muscle cells, but not orbital fibroblasts, in serum from patients with TAO in antibody-dependent cell-mediated cytotoxicity (ADCC) (54–57). It seems likely that such antibodies play a role in the development of the ocular myopathy subtype of TAO, although the target antigen(s) has not been identified. D.

Other Antibodies

Some other eye muscle antigens were also identified by cloning an eye muscle expression library with patient antibodies or oligonucleotides, including the calcium-binding protein calsequestrin (41), the tissue nonspecific protein 1 D (38), and sarcolumenin (Wall et al., unpublished data). Antibodies against the 63 kDa protein calsequestrin were found in about 30% of patients with TAO and in a few normal subjects (41). Although not closely


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related to ophthalmopathy, such antibodies are another example of secondary immune reaction following eye muscle membrane damage and release of intracellular proteins. Antibodies to sarcolumenin are likewise found in a small proportion of patients with ophthalmopathy and eye muscle damage (Wall et al., unpublished data).

IV.

ANIMAL MODELS

In recent animal studies thyroiditis has been induced in naive BALB/c and NOD mice by immunizing with human TSHR, either expressed as a bacterial fusion protein or by genetic immunization (58–60). In initial studies, carried out by Ludgate and colleagues, BALB/c mice developed a Th2-like response to the receptor while NOD mice developed a Th1-like response with thyrocyte destruction (58). Orbital infiltration by mast cells and lymphocytes, and adipose accumulation, was found in 68% of the BALB/c mice but in none of the NOD mice (59). These authors proposed that a Th2 autoimmune response against a TSHR protein in the preadipocyte cell was the initiating event for ophthalmopathy in their model. In our own studies currently underway we have obtained similar results in BALB/c and outbred mice immunized with cDNAs for G2s and the TSHR (8). Groups of mice were immunized with G2s, G2s and TSH receptor, G2s and IL-4 (to bias to a Th2 autoimmune reaction), G2s and IL-12 (to bias to a Th1 reaction), and empty carrier as control. Serum from mice immunized with G2s contained antibodies to G2s, beginning at about week 3 and increasing throughout weeks 12–16 of the study. Antibodies to Fp were also produced, but generally later than those to G2s, and levels were greater (Figs. 2, 3). These results strongly confirm our clinical findings that antibodies against Fp are

Figure 2 Serial levels of serum antibodies against G2s (upper panel) and Fp (lower panel) in individual outbred mice immunized with cDNA for G2s, G2s ⫹ TSH-R, G2s ⫹ IL-4, G2s ⫹ IL-12, or sucrose as control. Results are expressed as optical density at 405 nM in ELISA.

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Figure 3 Mean serum antibodies against G2s (upper panel) and Fp (lower panel) in mice immunized with cDNA for G2s, G2s ⫹ TSH-R [‘‘TSHR’’], G2s ⫹ IL-4 [‘‘IL-4’’], G2s ⫹ IL-12 [‘‘IL-12’’] or empty carrier, assessed at 17 wk. TSHR ⫽ Thyrotropin receptor, IL-12 ⫽ interleukin-12, IL-4 ⫽ interleukin-4. Results are expressed as mean (⫹/⫺ SD) optical density at 405 nM in ELISA. Statistical analyses refer to unpaired Student’s ‘‘t’’ tests, where a P value of ⬍0.05 is taken as significant. secondary to the eye muscle damage induced by autoimmunity against some other protein, such as G2s, in eye muscle membranes. There was no obvious ophthalmopathy in these mice. On histological examination of the orbital tissues from G2s-immunized mice the only abnormalities were mild inflammation with lymphocytes and inflammatory cells and some separation of eye muscle fibers (8). In current experiments we are immunizing mice with cDNAs for collagen XIII, an antigen associated with the congestive ophthalmopathy subtype of TAO (61), and Fp, and carrying out the same tests. We are also measuring expression of G2s and Fp in eye muscle membranes, cytokine expression in the orbital tissues, and cytotoxic T-lymphocyte reactivity against autologous eye muscle cells. With the availability of a fully developed model equivalent to the human disease it will be possible to address the key questions, including the following: Does radioactive iodine treatment of the associated hyperthyroidism lead to worsening of eye disease or its development? What is the relationship between the eye muscle and orbital connective tissue components of TAO? What is the initial reaction leading to the development of orbital inflammation in patients with thyroid autoimmunity? The possible role of cytotoxic antibodies in ADCC can also be assessed. V.

CONCLUSION

Recognition of a TSHR protein in orbital preadipocytes by circulating antibodies targeted to the thyrocyte TSHR may be the initial event leading to homing of lymphocytes into orbital tissue. In the course of Graves’ inflammation, antibodies and T cells reactive against


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G2s may react with G2s expressed in thyroid membrane and in the eye muscle fiber, and this may be a factor leading to eye muscle damage and dysfunction. Antibodies against Fp are secondary to eye muscle fiber damage but sensitive markers of immune-mediated fiber necrosis in patients with Graves’ hyperthyroidism. A recently developed experimental model for TAO provides a promising insight into the early stages of ophthalmopathy and its evolution. REFERENCES 1. Weetman AP. Thyroid-associated eye disease: pathophysiology. Lancet 1991; 338:25–28. 2. Yamada M, Li AW, Wall JR. Thyroid-associated ophthalmopathy: clinical features, pathogenesis and management. Crit Rev Clin Lab Sci 2000; 37:523–549. 3. Bahn RS, Heufelder AE. Pathogenesis of Graves’ ophthalmopathy. N Engl J Med 1993; 329: 1468–1475. 4. Teng CS, Yeo PP. Ophthalmic Graves’ disease: natural history and detailed thyroid function studies. Br Med J 1977; 1:273–275. 5. Salvi M, Zhang ZG, Haegert D, et al. Patients with endocrine ophthalmopathy not associated with overt thyroid disease have multiple thyroid immunological abnormalities. J Clin Endocrinol Metab 1990; 70:89–94. 6. Burch HB, Wartofsky L. Graves’ ophthalmopathy: current concepts regarding pathogenesis and management. Endocr Rev 1993; 14:747–793. 7. Solovyena TP. Endocrine ophthalmopathies. Problems of rational classification. Orbit 1989; 3:193–198. 8. Yamada M, Li AW, Chang H-C, Watanabe C, Wall JR. A model for thyroid-associated ophthalmopathy in BALB/C mice immunized with thyrotrophin receptor and G2s. In: Proceedings 12th International Thyroid Congress, Kyoto, Japan, October 2000; (abstract P-366/D). 9. Ross PV, Koenig RJ, Arscott P, et al. Tissue specificity and serologic reactivity of an autoantigen associated with autoimmune thyroid disease. J Clin Endocrinol Metab 1992; 77:433–438. 10. Weetman AP. Thyroid-associated ophthalmopathy. Autoimmunity 1992; 12:215–222. 11. Bahn RS. The fibroblast is the target cell in the connective tissue manifestations of Graves’ disease. Int Arch Allergy Immunol 1995; 106:213–218. 12. Heufelder AE. Involvement of the orbital fibroblast and TSH receptor in the pathogenesis of Graves’ ophthalmopathy. Thyroid 1995; 5:331–340. 13. Feliciello A, Porcellini A, Ciullo I, et al. Expression of thyrotropin-receptor mRNA in healthy and Graves’ disease retro-orbital tissue. Lancet 1993; 342:337–338. 14. Endo T, Ohta K, Haraguchi K, et al. Cloning and functional expression of a thyrotropin receptor cDNA from rat fat cells. J Biol Chem 1995; 270:10833–10837. 15. Chang TC, Chang TJ, Huang YS, et al. Identification of autoantigen recognized by autoimmune ophthalmopathy sera with immunoblotting correlated with orbital computed tomography. Clin Immunol Immunopathol 1992; 65:161–166. 16. Kiljanski JI, Nebes V, Wall JR. The ocular muscle cell is a target of the immune system in endocrine ophthalmopathy. Int Arch Allergy Immunol 1995; 106:204–212. 17. Wall JR, Salvi M, Bernard NF, et al. Thyroid-associated ophthalmopathy—a model for the association of organ-specific autoimmune disorders. Immunol Today 1991; 12:150–153. 18. Wall J. Extrathyroidal manifestations of Graves’ disease. Editorial. J Clin Endocrinol Metab 1995; 80:3427–3429. 19. Wall JR, Bernard N, Boucher A, et al. Pathogenesis of thyroid-associated ophthalmopathy: an autoimmune disorder of the eye muscle associated with Graves’ hyperthyroidism and Hashimoto’s thyroiditis. Clin Immunol Immunopathol 1993; 68:1–8. 20. Riley FC. Orbital pathology in Graves’ disease. Mayo Clin Proc 1972; 47:975–979. 21. Trokel SL, Jakobiec FA. Correlation of CT scanning and pathologic features of ophthalmic Graves’ disease. Ophthalmology 1981; 88:553–564.

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22. Smith TJ, Bahn RS, Gorman CA. Connective tissue, glycosaminoglycans, and diseases of the thyroid. Endocr Rev 1989; 10:366–391. 23. Tallstedt L, Norberg R. Immunohistochemical staining of normal and Graves’ extraocular muscle. Invest Ophthalmol Vis Sci 1988; 29:175–184. 24. Hufnagel TJ, Hickey WF, Cobbs WH, et al. Immunohistochemical and ultrastructural studies on the exenterated orbital tissues of a patient with Graves’ disease. Ophthalmology 1984; 91: 1411–1419. 25. Kroll AJ, Kuwabara T. Dysthyroid ocular myopathy. Anatomy, histology, and electron microscopy. Arch Ophthalmol 1966; 76:244–247. 26. Weetman AP, Cohen S, Gatter KC, et al. Immunohistochemical analysis of the retrobulbar tissues in Graves’ ophthalmopathy. Clin Exp Immunol 1989; 75:222–227. 27. Heufelder AE, Bahn RS. Detection and localization of cytokine immunoreactivity in retroocular connective tissue in Graves’ ophthalmopathy. Eur J Clin Invest 1993; 23:10–17. 28. Campbell RJ. Pathology of Graves’ Ophthalmopathy. New York: Raven Press, 1984. 29. Weetman AP. Autoimmunity in Graves’ ophthalmopathy. J R Soc Med 1989; 82:153–158. 30. Kubota S, Gunji K, Ackrell BA, et al. The 64-kilodalton eye muscle protein is the flavoprotein subunit of mitochondrial succinate dehydrogenase: the corresponding serum antibodies are good markers of an immune-mediated damage to the eye muscle in patients with Graves’ hyperthyroidism. J Clin Endocrinol Metab 1998; 83:443–447. 31. Gunji K, De Bellis A, Kubota S, et al. Serum antibodies against the flavoprotein subunit of succinate dehydrogenase are sensitive markers of eye muscle autoimmunity in patients with Graves’ hyperthyroidism. J Clin Endocrinol Metab 1999; 84:1255–1262. 32. Gunji K, De Bellis A, Kubota S, et al. Cloning and characterization of the novel thyroid and eye muscle shared protein G2s-autoantibodies against G2s are closely associated with ophthalmopathy in patients with Graves’ hyperthyroidism. J Clin Endocrinol Metab 2000; 85: 1641–1647. 33. Nauman JA. Biological activity of antibodies circulating in endocrine ophthalmopathy. Dev Ophthalmol 1993; 25:29–37. 34. Kodama K, Sikorska H, Bandy DP, et al. Demonstration of a circulating autoantibody against a soluble eye-muscle antigen in Graves’ ophthalmopathy. Lancet 1982; 2:1353–1356. 35. Kadlubowski M, Irvine WJ, Rowland AC. The lack of specificity of ophthalmic immunoglobulins in Graves’ disease. J Clin Endocrinol Metab 1986; 63:990–995. 36. Ahmann A, Baker JR, Jr, Weetman AP, et al. Antibodies to porcine eye muscle in patients with Graves’ ophthalmopathy: identification of serum immunoglobulins directed against unique determinants by immunoblotting and enzyme-linked immunosorbent assay. J Clin Endocrinol Metab 1987; 64:454–460. 37. Kubota S, Gunji K, Stolarski C, et al. Reevaluation of the prevalences of serum autoantibodies reactive with ‘‘64-kDa eye muscle proteins’’ in patients with thyroid-associated ophthalmopathy. Thyroid 1998; 8:175–179. 38. Dong Q, Ludgate M, Vassart G. Cloning and sequencing of a novel 64-kDa autoantigen recognized by patients with autoimmune thyroid disease. J Clin Endocrinol Metab 1991; 72:1375–1381. 39. ID Zhang ZG, Salvi M, Miller A, Bernard N, Arthurs B, Wall JR. Restricted tissue reactivity of autoantibodies to a 64 kDa eye muscle membrane antigen in thyroid-associated ophthalmopathy. Clin Immunol Immunopathol 1992; 62:183–189. 40. Zhang ZG, Rodien P, Dong Q, Bernard NF, Salvi M, Miller A, Vassart G, Ludgate M, Wall JR. Autoantibodies in the serum of patients with autoimmune thyroid disorders react with a recombinant 98 amino acid fragment of a 64 kDa eye muscle recombinant protein which is also expressed in the thyroid. Autoimmunity 1992; 13:151–157. 41. Gunji K, Kubota S, Stolarski C, et al. A 63 kDa skeletal muscle protein associated with eye muscle inflammation in Graves’ disease is identified as the calcium binding protein calsequestrin. Autoimmunity 1999; 29:1–9. 42. Kubota S, Gunji K, Stolarski C, et al. Role of eye muscle antibody measurement in diagnosis of thyroid-associated ophthalmopathy: a laboratory update. Endocr Pract 1998; 4:127–132.


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43. Salvi M, Miller A, Wall JR. Human orbital tissue and thyroid membranes express a 64 kDa protein which is recognized by autoantibodies in the serum of patients with thyroid-associated ophthalmopathy. FEBS Lett 1988; 232:135–139. 44. Salvi M, Bernard N, Miller A, et al. Prevalence of antibodies reactive with a 64 kDa eye muscle membrane antigen in thyroid-associated ophthalmopathy. Thyroid 1991; 1:207–213. 45. Miller A, Arthurs B, Boucher A, et al. Significance of antibodies reactive with a 64 kDa eye muscle membrane antigen in patients with thyroid autoimmunity. Thyroid 1992; 2:197–202. 46. Wu YJ, Clarke EM, Shepherd P. Prevalence and significance of antibodies reactive with eye muscle membrane antigens in sera from patients with Graves’ ophthalmopathy and other thyroid and nonthyroid diseases. Thyroid 1998; 8:167–174. 47. Wall J, Barsouk A, Stolarski C, et al. Serum eye muscle and TSH receptor antibodies predicted the development of ophthalmopathy in a euthyroid subject with a family history of autoimmunity. Thyroid 1998; 6:353–358. 48. Gunji K, Skolnick C, Bednarczuk T, Benes S, Ackrell BA, Cochran B, Kennerdell JS, Wall JR. Eye muscle antibodies in patients with ocular myasthenia gravis: possible mechanism for eye muscle inflammation in acetylcholine-receptor antibody-negative patients. Clin Immunol Immunopathol 1998; 87:276–281. 49. Archibald C, Kaspar M, Cheng H-C, Ackrell BAC, Li AW, Yamada M, De Bellis AM, Wall JR. Orbital antibodies and subclass of ophthalmopathy. Proceedings, International Symposium on Thyroid Associated Ophthalmopathy, Kyoto, Japan, October 2000. Thyroid (suppl) (in press). 50. Paschke R, Metcalfe A, Alcalde L, et al. Presence of nonfunctional thyrotropin receptor variant transcripts in retroocular and other tissues. J Clin Endocrinol Metab 1994; 79:1234–1238. 51. Karlsson F, Dahlberg PA, Jansson R, et al. Importance of TSH receptor activation in the development of severe endocrine ophthalmopathy. Acta Endocrinol (suppl) 1989; 121:132–141. 52. Bahn RS, Dutton CM, Natt N, et al. Thyrotropin receptor expression in Graves’ orbital adipose/connective tissues: potential autoantigen in Graves’ ophthalmopathy. J Clin Endocrinol Metab 1998; 83:998–1002. 53. Major BJ, Cures A, Frauman AG. The full length and splice variant thyrotropin receptor is expressed exclusively inskeletal muscle of extraocular origin: a link to the pathogenesis of Graves’ ophthalmopathy. Biochem Biophys Res Commun. 1997; 23;230:493–496. 54. Wang PW, Hiromatsu Y, Laryea E, Wosu L, How J, Wall JR. Immunologically-mediated cytotoxicity against human eye muscle cells in Graves’ ophthalmopathy. J Clin Endocrinol Metab 1986; 63:316–322. 55. Hiromatsu Y, Wang PW, Wosu L, How J, Wall JR. Mechanisms of immune damage in Graves’ ophthalmopathy. Horm Res 1987; 26:198–207. 56. Hiromatsu Y, Fukazawa H, How J, Wall JR. Antibody-dependent cell-mediated cytotoxicity against human eye muscle cells and orbital fibroblasts in Graves’ ophthalmopathy—roles of Class II MHC antigen expression and gamma-interferon actions on effector cells. Clin Exp Immunol 1987; 70:593–603. 57. Hiromatsu Y, How J, Miller A, Guinard F, Salvi M, Wall JR. A new thyroid cytotoxic antibody that cross-reacts with an eye muscle cell surface antigen may be the cause of thyroid-associated ophthalmopathy. J Clin Endocrinol Metab 1988; 67:565–570. 58. Costagliola S, Rodien P, Many MC, et al. Genetic immunization against the human thyrotropin receptor causes thyroiditis and allows production of monoclonal antibodies recognizing the native receptor. J Immunol 1998; 160:1458–1465. 59. Many MC, Costagliola S, Detrait M, et al. Development of an animal model of autoimmune thyroid eye disease. J Immunol 1999; 162:4966–4974. 60. Ludgate M, Crisp M, Lane C, et al. The thyrotropin receptor in thyroid eye disease. Thyroid 1998; 8:411–413. 61. Wall JR, Blanchard ME, West K, et al. Autoantibodies against the plasm membrane protein type XIII collagen are new markers of congestive ophthalmopathy. 72nd Annual meeting of the American Thyroid Association, Portland, OR, September 1999. Thyroid (suppl):50 (abstract).

24 Glycosaminoglycans in Graves’ Orbitopathy GEORGE J. KAHALY Gutenberg University Hospital, Mainz, Germany

I.

INTRODUCTION

Glycosaminoglycans (GAG) are linear polysaccharides found ubiquitously in extracellular matrix, on cell surfaces, and in the intracellular compartment of mast cells (heparin). GAG macromolecules are characterized by a strong polyanionic and hydrophilic charge. After synthesis onto core proteins in the Golgi apparatus within the fibroblasts and related cells, the abundant majority of GAG is released into the extracellular matrix where they are bound to structural proteins to form proteoglycans. Free GAG chains are encountered in considerable amounts in the blood from where they are eliminated in the kidney. GAG as major compounds of proteoglycans in the extracellular matrix, are essential for the structure and function of connective tissues. The strong polyanionic and hydrophilic charge of GAG components, which is fundamental for the water content and electrolyte composition of the extracellular space, is due to multiple carboxyl and sulfate residues. These linear polysaccharides are composed of repetitive disaccharides consisting of one hexosamine (d-glucosamine, d-galactosamine) and one uronic acid (d-glucuronic acid, l-iduronic acid). Different substitutions and structures of the disaccharides allow the formation of various GAG components, including hyaluronic acid (HA), chondroitin sulfate (CS), and dermatan sulfate (DS), with highly variable charge and chain lengths (1–6). GAGs take part in extracellular matrix organization, the regulation of cell proliferation and differentiation, regulation of diffusion of macromolecules through tissues, growth factor attachment, cell-to-cell interaction, and regulation of interleukin-1 (IL-1) production in local inflammatory response. HA is the largest GAG molecule, containing several thousand repeated disaccharides. In contrast to the other GAG components, HA is unsulfated. Binding to HA generally takes place through specific, noncovalent interactions of proteins 235

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and other organic molecules to a defined binding site of several disaccharide units on the HA monomer. One HA backbone molecule can associate with up to 200 proteoglycans through stabilizing link proteins to form large space-consuming herringbone aggregates with molecular weights from 5 ⫻ 107 to 5 ⫻ 108. These are essential for the water and electrolyte content of the extracellular matrix. Recent results of histochemical, biochemical, and clinical studies provide strong evidence for an involvement of connective tissue in autoimmune diseases. Specific HA, HS, and other polysulfated GAG antibodies were studied in sera of patients with Graves’ orbitopathy (GO), and a GAG-stimulatory lymphokine that selectively increases GAG synthesis in normal human dermal fibroblasts has been demonstrated. Furthermore, the role of cell surface HA receptor CD44 in T-cell activation and proliferation has been shown. Cell surface HA receptors (CD44) are expressed on a variety of immune-competent cells and tissue cells, including lymphocytes, monocytes, granulocytes, medullar thymocytes, erythrocytes, epithelial cells, fibroblasts, skeletal muscle, and tumor cells (7–12). Proptosis, a prominent feature in patients with GO, is mainly caused by enhanced GAG deposition in the orbital space. Histological examination of orbital tissue in GO demonstrates mononuclear cell infiltration including activated, somatostatin-receptor bearing T cells, a few B cells, and macrophages. A current hypothesis is that cytokines released by immunocompetent cells stimulate orbital fibroblasts to proliferate and to secrete GAG in GO patients. As well as the increased GAG production, an alteration of the structure and distribution pattern of single GAG components may be the cause for an increased water-binding capacity of orbital connective tissue in GO (13–22). The biochemical composition of these hydrophilic polysaccharides has been determined by a sensitive and highly reproducible method.

II. CONCENTRATION OF GAG IN ORBITAL TISSUE Based on our studies total tissue GAG is markedly increased in GO patients as compared to normal controls (Fig. 1). In comparison, the protein concentration in orbital connective and adipose tissue is similar in both groups. Marked differences in the tissue fraction of CS, DS, and HA can also be detected. CS is the major GAG compound in orbital connec-

Figure 1 Concentration of total GAG (µg/g wet tissue) in orbital tissue of both patients with GO as well as controls (data shown as mean ⫾ SEM).

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Figure 2 Distribution pattern (displayed as percentage) of orbital GAG in GO patients and controls.

tive tissue of patients with GO, whereas DS is dominant in controls (Fig. 2). The ratio of HA content in relation to total GAG concentration shows no difference. An increase in the several disaccharide digestion products of CS, DS (Di-6S, p ⫽ 0.0001, Fig. 3; Di0S, Di-4S, and Di-diS2, p ⬍ 0.05); and HA (Di-UA2S, p ⬍ 0.0001) is seen in patients in comparison to controls. Orbital tissue content of the HA disaccharide Di-HA and the Di-diS1 disaccharide of CS and DS show no alterations. In our study the ratio of sulfated vs. total disaccharides was 85 ⫾ 6% in Graves’ patients and only 65 ⫾ 5% in controls (p ⬍ 0.05, Fig. 4). We found a similar distribution of GAG content of orbital tissue, urine, and serum samples obtained at the same time, in three patients with severe and clinically active GO, and all measurements from Graves’ patients were markedly increased (p ⬍ 0.0001) in comparison to controls. We did not find a correlation between orbital and peripheral GAG values, and thyroid-stimulating hormone (TSH)-receptor autoantibody titers. III. DISCUSSION In our laboratory, for the first time, the distribution pattern and biochemical composition of the major GAG components CS, DS, and HA have been quantified in orbital tissue of GO patients and in controls by high-performance liquid chromatographic (HPLC) analysis. In GO patients we noted a marked increase of all three GAG molecules and a shift to

Figure 3 Amount of disaccharide-6-sulfate in the orbital tissue (µg/g tissue) in patients with GO and control subjects (data shown as mean ⫾ SEM).

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Figure 4 Ratio sulfated disaccharides/total disaccharides in orbital tissue of GO patients and controls (data shown as mean ⫾ SEM).

higher sulfated, negatively charged compounds, making them especially potent as waterbinders. Thus, structural alteration of GAG may elucidate the massive increase of the orbital volume, leading to an elevated pressure in the bony orbit and to displacement of the globe anteriorly. Structural modifications of all GAG components, which may reflect pathological alterations, can be examined directly on the basis of the disaccharide HPLC-elution pattern. By means of this column it is possible to separate uncharged, low charged, and high charged disaccharide units and to determine the absolute concentration of the different GAG compounds. In previous work, the results of the urinary disaccharide analysis showed a marked increase in total GAG as well as CA, DS, and HA concentrations in patients with GO in comparison to healthy controls. The major portion of the elevated GAG is represented by CA, which can be related to the findings in normal urine samples where low-molecular-weight CA and heparan sulfate are the major urinary GAG compounds. DS and HA, which are detected in low concentrations in urinary samples of GO patients and controls, are also elevated. Elevated GAG synthesis by stimulated cultured orbital fibroblasts from GO patients has been reported (35). In this paper, analysis of orbital GAG showed that the highly sulfated CS represented the major portion of orbital GAG in patients (48%), whereas DS was dominant in controls (46%). The tissue fraction of HA, which does not contain sulfate residues, was similar in both groups (22 vs. 23%). CS was also the most prominent GAG compound in serum and urine samples. A previous publication investigating the biochemical composition of orbital tissue in human cadavers 48 h postmortem by cetylpyridinium chloride (CPC)-cellulose chromatography described that HA (51% of total GAG) and DS (31%) were the two major GAG components (36). The different GAG distributions in the two studies may be related to an overestimation of HA caused by coelution of HA with structurally related GAG components at similar salt concentrations, and/or to the fact that GAG concentration was only measured by quantification of the uronic acid portions of GAG (31). GAG synthesis by human orbital fibroblasts of GO patients is influenced by several cytokines derived from activated T lymphocytes and macrophages (37). IL-1 receptor antagonists and soluble IL-1 receptors significantly inhibit stimulation of GAG synthesis in orbital fibroblasts by IL-1. Furthermore, IL-1 and TGF-1β increase the rate of [S-35] sulfate incorporation into proteoglycans two to five times over controls in cultured orbital fibroblasts (38). IL-1 increases [S-35] sulfate incorporation into proteoglycan by increas-

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Figure 5 Mechanisms for increased GAG deposition into the orbit.

ing the net increase of proteoglycan synthesis and by increasing the number of GAG chains attached to core protein in vitro. Imai et al. (37) showed that IL-1 and TGF-1β did not change the size of GAG chains in vitro. However, stimulation analysis of cultured orbital fibroblasts may not completely correspond to the findings in vivo. In comparison, HPLC disaccharide analysis reveals that GAG contains elongated chains composed of monosulfated CS, DS disaccharides (Di-6S, Di-4S), and oversulfated CS, DS compounds (Di-diS1, Di-diS2), showing that significant oversulfation of GAG chains is present in GO patients. Thus, different mechanisms for an increased GAG deposition into the orbital tissue are possible, including net increase of proteoglycan synthesis, increase of both number of GAG chains and GAG-producing cells, elongation, oversulfation, and/or decreased GAG degradation (Fig. 5). A comparable orbital and peripheral GAG distribution in patients with GO was observed. In this sense, multifocal fibroblast activation with resulting overproduction of certain GAG compounds, especially CS, leads to the hypothesis that we are dealing with a systemic autoimmune disease.

IV.

SUMMARY

Accumulation of interstitial GAG in orbital tissue of patients with GO leads to edema, increased orbital pressure, and proptosis. Total tissue GAG is elevated in GO patients and the various GAG polymers show significant differences in distribution. CS, HA, and DS are all elevated compared to normal controls. In GO patients, CS is the major GAG component whereas DS is dominant in controls (46 ⫾ 8 vs. 30 ⫾ 5%). The sulfated disaccharide digestion products are also markedly increased in patients, and the ratio of sulfated vs. total disaccharide content is higher in patients compared to controls. Since accumulation of negatively charged sulfate residues in GAG disaccharides results in enhanced waterbinding capacity, as well as inflammation and increased volume of the orbital adipose tissue, the altered structure and nature of sulfated GAG units in the orbit may be responsible for the pathogenic changes in Graves’ orbitopathy.

REFERENCES 1. Newton DJ, Scott JE, Ahmad S. Circadian rythmus and the urinary excretion of acid glycosaminoglycans in normal human adults. Connective Tissue Res 1979; 7:47–55. 2. Iozzo RU. Proteoglycans: structure, function and role in neoplasia. Lab Invest 1985; 53:373– 395.

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3. Poulsen JH. Urine and tissue glycosaminoglycans and their interrelations. Dan Med Bull 1986; 33:75–96. 4. Heinegard D, Sommarin Y. Proteoglycans: an overview. Meth Enzymol 1987; 144:319–372. 5. Ruoslahti E. Structure and biology of proteoglycans. Annu Rev Cell Biol 1988; 4:229–255. 6. Wight TN, Heinegard DK, Hascall VC. Proteoglycans, structure and function. In: Hay ED, ed. Cell Biology of Extracellular Matrix, 2nd ed. New York: Plenum Press, 1991: 45–78. 7. Kahaly G, Hansen C, Stover C, Beyer J, Otto E. Glycosaminoglycan antibodies in endocrine ophthalmopathy. Horm Metab Res 1993; 25:637–639. 8. Hansen C, Irmscher A-K, Kuhlemann K, Beyer J, Kahaly G. Insulin-dependent diabetes mellitus and glycosaminoglycans. Horm Metab Res 1995; 27:555–558. 9. Hansen C, Otto E, Kuhlemann K, Fo¨rster G, Kahaly G. Glycosaminoglycans in autoimmunity. Clin Exp Rheumatol 1996; 14:59–67. 10. Aruffo A, Stamenkovic I, Melnick M, Underhill CB, Seed B. CD44 is the principal cell surface receptor for hyaluronate. 1990; Cell 61:1303–1313. 11. Conrad P, Rothmann BL, Kelly KA, Blue ML. Mechanism of peripheral T cell activation by coengagement of CD44 and CD2. J Immunol 1992; 149:1830–1833. 12. Koenig A, Norgard-Sumnicht K, Linhardt R, Varki A. Differential interactions of heparin and heparan sulfate glycosaminoglycans with selectins. J Clin Invest 1998; 101:877–889. 13. Kahaly G, Stover C, Otto E, Beyer J, Schuler M. Glycosaminoglycans in thyroid-associated ophthalmopathy. Autoimmunity 1992; 13:81–88. 14. Kahaly G, Stover C, Beyer J, Otto E. In vitro synthesis of glycosaminoglycans in endocrine ophthalmopathy. Acta Endocrinol 1992; 127:397–402. 15. Kahaly G, Hansen C, Stover C, Kuhlemann K, Beyer J, Otto E. Glycosaminoglycans and endocrine orbitopathy. Exp Clin Endocrinol 1994; 102:151–161. 16. Kahaly G, Hansen C, Felke B, Dienes HP. Immunohistochemical staining of retrobulbar adipose tissue in Graves’ ophthalmopathy. Clin Immunol Immunopathol 1994; 73:53–62. 17. Otto E, Ochs K, Hansen C, Wall J, Kahaly GJ. Orbital tissue-derived T lymphocytes from patients with Graves’ ophthalmopathy recognize autologous orbital antigens. J Clin Endocrinol Metab 1996; 81:3045–3050. 18. Kahaly G, Otto E, Fo¨rster G, et al. T cells and orbital connective tissue in endocrine orbitopathy. Exp Clin Endocrinol Diabetes 1996; 104:79–83. 19. Otto E, Fo¨rster G, Kuhlemann K, Hansen C, Kahaly G. TSH receptor in endocrine autoimmunity. Clin Exp Rheumatol 1996; 14:77–84. 20. Fo¨rster G, Otto E, Hansen C, Ochs K, Kahaly G. Analysis of orbital T cells in thyroid-associated ophthalmopathy. Clin Exp Immunol 1998; 112:427–434. 21. Kahaly G, Diaz M, Hahn K, Beyer J, Bockisch A. Indium-111-pentetreotide scintigraphy in Graves’ ophthalmopathy. J Nucl Med 1995; 36:550–554. 22. Kahaly G, Go¨rges R, Diaz M, Hommel G, Bockisch A. Indium-111-pentetreotide in Graves’ disease. J Nucl Med 1998; 39:533–536. 23. Bitter T, Muir HM. A modified uronic acid carbazole reaction. Anal Biochem 1962; 4:330– 334. 24. Pennock CA. A review and selection of simple laboratory methods used for the study of glycosaminoglycan excretion and diagnosis of the mucopolysaccharidoses. J Clin Pathol 1976; 29:111–123. 25. Kahaly G, Schuler M, Sewell AC, Bernhard G, Beyer J, Krause U. Urinary glycosaminoglycans in Graves’ ophthalmopathy. Clin Endocrinol 1990; 33:35–44. 26. Schuler M, Hansen C, Winand R, Stover C, Otto E, Beyer J, Kahaly G. Urinary and plasma glycosaminoglycans in endocrine ophthalmopathy. In: Kahaly G, ed. Endocrine Ophthalmopathy. Molecular, Immunological and Clinical Aspects. Basel: Karger Publishers, 1993. 27. Kahaly G, Hansen C, Beyer J, Winand R. Plasma glycosaminoglycans in endocrine ophthalmopathy. J Endocrinol Invest 1994; 17:45–50. 28. Gurr E, Pallasch G, Tunn S, Tamm C, Delbru¨ck A. High performance liquid chromatographic

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25 The Risk of Orbital Disease Following Radioactive Iodine Treatment LEIF TALLSTEDT St. Erik’s Eye Hospital, Karolinska Institute, Stockholm, Sweden

I.

INTRODUCTION

Graves’-associated orbital disease is often seen in a close temporal relation to Graves’ thyroid disease (1,2). In the majority of patients the eye signs develop after the first signs of hyperthyroidism, and several patients will deteriorate after treatment for the thyroid disease has been initiated. The orbital disease and thyroid disease are both manifestations of Graves’ disease, but the observation that the eye disease often develops after the thyroid disease has evoked the idea that the treatment and management of the thyroid disease might affect the course of the orbital disease. This subject has been debated for many years, and is still debated. This chapter will review some of the existing studies, and discuss other possible risk factors for the development of the orbital disease. II. TREATMENT OF HYPERTHYROIDISM AND THE COURSE OF GRAVES’ ORBITAL DISEASE Several earlier studies report the development of orbital disease in relation to only one type of antithyroid treatment, but other studies compare two or three treatment forms. The outcome of these comparative studies is summarized in Table 1. These studies have limited value since many were not randomized, several contain few patients, follow-up time varies, and the eye examination is often inadequate (3–6). One of the retrospective studies, however, comprises a large number of patients. Sridama and DeGroot reviewed 506 evaluable patients with Graves’ disease, equally distributed between the three treatment forms 243

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Table 1 Outcome of Graves’ Orbital Disease After Treatment for Graves’ Disease in Comparative Studies Reference Hamilton et al. (3) Barbosa et al. (4) Gwinup et al. (5) Calissendorf et al. (6) Sridama and DeGroot (7) Va´zquez-Chavez et al. (9) Fernańdez-Sańchez et al. (10) Bartalena et al. (15) Tallstedt et al. (11)

Antithyroid drugs ⫹ W ND ND ⫹ ⫹

Surgery

131

ND ⫹ ⫹ ND ND ND ⫹

ND (W) ⫹ ND ND ND W W W

⫹

I

ND, no difference; ⫹, treatment modality included in the study; W, higher frequency of ophthalmopathy.

(7). Among the 288 patients without clinical evidence of orbital disease before therapy, the incidence of orbital disease was 6.7% in the medically treated, 7.1% in the surgically treated, and 4.9% in the 131 I-treated group (not significantly different). In 218 patients who already had ocular signs before treatment, approximately 20% in each group developed notable progression of these signs. The authors concluded that the choice of treatment did not influence the clinical course of the orbital disease. The results of this study should be interpreted with some caution. Eighty of the patients (16%) received more than one form of treatment, and another 91 patients (18%) had received prior treatment in other hospitals before being referred. Patients differed in several baseline characteristics, such as age, thyroid gland size, gender, and thyroid hormone levels. Surgically treated patients were younger and had higher thyroid hormone levels, a fact that can influence the outcome of orbital disease, and this will be discussed later. Another flaw of this study is that the follow-up period was as long as 5.0 ⫾ 3.2 years (range, 1–11 years). A recommended follow-up time between therapy and assessment of results is 3–6 months, so that spontaneous improvement or worsening of the orbital disease would be less likely (8). In a small, randomized study, Va´zquez-Cha´vez et al. (9) evaluated 20 patients treated with 131 I and 20 patients treated with thyroidectomy and evaluated only the effect on exophthalmos. They did not find any difference between the two treatment groups after a follow-up time varying from 2 to 162 months. In a study of similar size, prospective but not randomized, Fernańdez Sańchez et al. (10) evaluated 21 patients treated with subtotal thyroidectomy and 24 patients treated with 131 I. All patients had Graves’ orbital disease and were pretreated with antithyroid drugs. Patients undergoing surgery improved significantly in the clinical score, Hertel exophthalmometry, and extraocular muscle diameter, whereas patients given 131 I improved significantly only in the clinical score. The authors concluded that the ophthalmopathy improved to a greater extent after surgery than after 131 I therapy. The follow-up time in this study was 12 months. The first randomized study comparing the three treatment forms was performed by Tallstedt et al. (11). The authors randomly assigned 179 patients with Graves’ disease with or without orbital disease to treatment with antithyroid drugs (10 mg methimazole four times daily for 18 months), subtotal thyroidectomy, or 131 I (intended dose to the thyroid: 120 Gy). The patients were stratified into two age groups, 20–34 years (antithy-

Orbital Disease After Radioactive Iodine Therapy

245

roid drugs or surgery) and 35–55 years, in which 131 I was included as a third treatment. The patients were evaluated up to 2 years after initiation of therapy. Nine patients with previous ocular signs deteriorated and 22 patients developed new infiltrative orbital disease. In the young age group there was no difference in the outcome of orbital disease between antithyroid drugs and surgery, whereas significantly more patients treated with 131 I (33%) in the older age group developed or experienced deterioration in already-present orbital disease, compared with treatment with antithyroid drugs (10%) and surgery (16%), respectively (p ⫽ 0.02). It was also found that, regardless of the type of therapy, the higher the pretreatment thyroid hormone levels, the higher the risk for ocular signs, and this was particularly apparent for the 131 I-treated patients (Fig. 1). Smoking was more common among the patients who had orbital disease during the study, but was not found to be a risk factor for development or deterioration of orbital disease (12). This study has been criticized mainly for the difference in thyroxine substitution between the treatment groups. At the start of the study, the clinical routine was to give thyroxine after 131 I therapy when there was biochemical evidence of hypothyroidism, whereas thyroxine was given earlier to patients treated with antithyroid drugs or thyroidectomy. This fact might have contributed to the outcome of the study. In a subsequent analysis, the investigators sought to evaluate whether the patients with orbital disease in the 131 I-treated group were hypothyroid to a greater extent, comparing the maximum serum thyroid-stimulating hormone (TSH) levels and minimum serum T3 and T4 levels after therapy, but this was not the case (13). Subsequently, the clinical routine was changed, and all patients treated with 131 I are given 0.05 mg thyroxine daily 2 weeks after therapy. The dosage is increased 0.1 mg daily after another 2 weeks to avoid posttherapy hypothyroidism. The effect of this change of therapy on the development of orbital disease has

Figure 1 Probability of the development or worsening of orbital disease in patients with hyperthyroidism caused by Graves’ disease. (From Ref. 11.)

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Tallstedt

been evaluated in a retrospective study (14). Of 244 patients given early thyroxine after 131 I therapy, 27 (11%) developed ocular signs, compared to 45 of 248 patients (18%) given thyroxine when hypothyroid (p ⫽ 0.04). A randomized, prospective study is underway comparing patients given 131 I and early thyroxine with patients treated with antithyroid drugs and similar thyroxine substitution. Similar results have been shown in a large study by Bartalena et al. (15). They evaluated 443 patients with slight or no ophthalmopathy, randomly assigned to receive 131 I only, 131 I followed by a 3-month course of prednisone, or methimazole for 18 months. With a follow-up time of 12 months, they found that orbital disease developed or worsened in 23 of 150 patients (15%) treated with 131 I only, in none of the 145 patients treated with 131 I and prednisone, and in 4 of the 148 patients (3%) treated with antithyroid drugs. Thus, the frequency of the development and worsening of orbital disease was significantly higher in the 131 I-treated group than in either the 131 I–prednisone group or the methimazole-treated

Figure 2 Serum concentration of TSH-receptor antibodies during the first 4 years after the three different forms of treatment for hyperthyroidism. (From Ref. 18.)


247

group (p ⬍ 0.001 for both comparisons). The ocular changes were mild and transient in the majority of patients, but 8 of the 23 patients in the 131 I group and 1 in the methimazole group subsequently required treatment for their orbital disease. Of the 72 patients in the 131 I-treated group who had orbital disease at baseline, none improved, compared to 50 of the 75 (67%) in the 131 I–prednisone group and 3 of the 74 (4%) in the methimazole group with orbital disease at baseline. The authors conclusion was that 131 I therapy is followed by the appearance or worsening of orbital disease more often than after therapy with antithyroid drugs. However, this worsening can be prevented by the administration of prednisone, which was also demonstrated earlier in another study by the same group (16). In view of the existing studies reviewed above, one can conclude that the treatment of hyperthyroidism can influence the progression of the orbital disease, and that the risk of deterioration seems to be higher after 131 I therapy. This might be explained by the release of antigens from the thyroid after radiation injury, or by a rise in activated peripheral T cells, which has been reported after 131 I therapy (17). The serum levels of TSH-receptor antibodies will, in most patients, slowly decrease after initiation of antithyroid drug treatment and after thyroidectomy. However, in almost all patients treated with 131 I there is an increase in serum concentration of these antibodies, followed by a slow decrease (18) (Fig. 2). There is increasing evidence that TSH receptors are present in the orbit, and it is possible that the TSH receptor antibodies play a role in the pathogenesis of the orbital disease. III. OTHER RISK FACTORS The risk of progression of orbital disease is presumably higher after 131 I therapy, but still the majority of 131 I-treated patients do not develop new eye changes or experience deterioration in existing eye changes. Few other risk factors for the orbital disease are known. However, smoking is now a well-established risk factor, which is reviewed elsewhere in this book. The serum level of TSH receptor antibodies has recently been shown to correlate with the clinical activity of the ocular signs in patients with active, moderately severe orbital disease (19). On the other hand, we have not been able to demonstrate that the serum level of TSH receptor antibodies at initiation of treatment for hyperthyroidism was a risk factor for later progression of orbital disease (11). As mentioned above, the serum level of thyroid hormones seems to be such a risk factor, particularly in patients treated with 131 I (Fig. 1). Thus, the severity of the hyperthyroidism might contribute to the progression of orbital disease. DeGroot et al. found in a retrospective study that progression of exophthalmos was significantly less common among patients who became hypothyroid after the first dose of 131 I than in those who continued to be thyrotoxic and had to be treated again (20). In our study, the majority of patients who experienced deterioration in their orbital disease needed more than one 131 I treatment (11). Pretreatment of orbital disease has also been shown to be a risk factor for severe ocular signs after 131 I therapy (21). Dysthyroidism is another possible risk factor, and meticulous control of the thyroid disease is important. Prummel et al. have demonstrated that dysthyroidism was associated with more severe ophthalmopathy (22), and that normalization of dysthyroidism was followed by an amelioration of the ocular signs (23). Karlsson et al. studied 30 patients with severe orbital disease, and found that in 15 the eye signs had followed upon a period of elevated serum TSH levels (24). The authors concluded that an increased stimulation of the thyroid, either by TSH or by TSH receptor antibodies, if induced during treatment for Graves’ disease, represents an important risk factor for severe eye disease. The possible

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importance of posttherapy hypothyroidism has been discussed above. In patients with orbital disease a dose of thyroxine is recommended, which will almost suppress the TSH production, after ablating any thyroid autonomous function. We believe that many patients will benefit from improvement in their eye signs following this treatment, but this has not been assessed in a clinical study. IV.

CONCLUSIONS

With regard to the existing randomized studies, one can conclude that 131 I therapy is likely to be followed by a somewhat higher risk of Graves’ orbital disease. However, the majority of 131 I-treated patients will not experience progression in their orbital disease. We still do not know enough about other risk factors in order to avoid deterioration in the ocular signs. A possible approach is to avoid 131 I therapy in patients with severe hyperthyroidism and orbital disease, using antithyroid drugs in these patients. If a definite treatment is necessary, a thyroidectomy should be performed. Another possible strategy is to give a 3-month course of steroids after the 131 I treatment, to prevent exacerbation of orbital disease. REFERENCES 1. Gorman CA. Temporal relationship between onset of Graves’ ophthalmopathy and diagnosis of thyrotoxicosis. Mayo Clin Proc 1983; 58:515–519. 2. Wiersinga WM, Smit T, van der Gaag R, Koornneef L. Temporal relationship between onset of Graves’ ophthalmopathy and onset of thyroidal Graves’ disease. J Endocrinol Invest 1988; 11:615–619. 3. Hamilton RD, Mayberry WE, McConahey WM, Hanson KC. Ophthalmopathy of Graves’ disease: a comparison between patients treated surgically and patients treated with radioiodide. Mayo Clin Proc 1967; 42:812–818. 4. Barbosa J, Wong E, Doe RP. Ophthalmopathy of Graves’ disease. Outcome after treatment with radioactive iodine, surgery, or antithyroid drugs. Arch Intern Med 1972; 130:111–113. 5. Gwinup G, Elias AN, Ascher MS. Effect on exophthalmos of various methods of treatment of Graves’ disease. JAMA 1982; 247:2135–2138. 6. Calissendorf BM, So¨derstro¨m M, Alveryd A. Ophthalmopathy and hyperthyroidism, a comparison between patients receiving different antithyroid treatments. Acta Ophthalmol 1986; 64: 698–703. 7. Sridama V, DeGroot LJ. Treatment of Graves’ disease and the course of ophthalmopathy. Am J Med 1989; 87:70–73. 8. Bahn RS, Gorman CA. Choice of therapy and criteria for assessing treatment outcome in thyroid-associated ophthalmopathy. Endocrinol Metab Clin North Am 1987; 16:391–407. 9. Va´zquez-Cha´vez C, Nishimura Meguro E, Espinosa Said L, Delgado Falfari A, Saínz de Viteri M. Influencia del tratamiento del hipertiroidismo en el curso del exoftalmos. Rev Invest Clin 1992; 44:241–247. 10. Fernańdez Sańchez JR, Rosell Pradas J, Carazo Martinez O, Torres Vela E, Escobar Jimenez F, Garbin Fuentes I, Vara Thorbeck R. Graves’ ophthalmopathy after subtotal thyroidectomy and radioiodine therapy. Br J Surg 1993; 80:1134–1136. 11. Tallstedt L, Lundell G, To¨rring O, Wallin G, Ljunggren J-G, Blomgren H, Taube A. Occurrence of ophthalmopathy after treatment for Graves’ hyperthyroidism. N Engl J Med 1992; 326:1733–1738. 12. Tallstedt L, Lundell G, Taube A. Graves’ ophthalmopathy and tobacco smoking. Acta Endocrinol (Copenh) 1993; 129:147–150.


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13. Tallstedt L, Lundell G. Radioiodine treatment, ablation and ophthalmopathy: a balanced perspective. Thyroid 1997; 7:241–245. 14. Tallstedt L, Lundell G, Blomgren H, Bring J. Does early administration of thyroxine reduce the development of Graves’ ophthalmopathy after radioiodine treatment? Eur J Endocrinol 1994; 130:494–497. 15. Bartalena L, Marcocci C, Bogazzi F, Manetti L, Tanda ML, Dell’Unto E, Bruno-Bossio G, Nardi M, Bartolomei MP, Lepri A, Rossi G, Martino E, Pinchera A. Relation between therapy for hyperthyroidism and the course of Graves’ ophthalmopathy. N Engl J Med 1998; 338:73– 78. 16. Bartalena L, Marcocci C, Bogazzi F, Panicucci M, Lepri A, Pinchera A. Use of corticosteroids to prevent progression of Graves’ ophthalmopathy after radioiodine therapy for hyperthyroidism. N Engl J Med 1989; 321:1349–1352. 17. Teng WP, Stark R, Munro AJ, McHardy Young S, Borysiewicz LK, Weetman AP. Peripheral blood T cell activation after radioiodine treatment for Graves’ disease. Acta Endocrinol (Copenh) 1990; 122:233–240. 18. To¨rring O, Tallstedt L, Wallin G, Lundell G, Ljunggren JG, Taube A, Saä¨f M, Hamberger B and the Thyroid Study Group. Graves’ hyperthyroidism: treatment with antithyroid drugs, surgery, or radioiodine—a prospective, randomized study. J Clin Endocrinol Metab 1996; 81: 2986–2993. 19. Gerding MN, van der Meer JWC, Broenink M, Bakker O, Wiersinga WM, Prummel MF. Association of thyrotrophin receptor antibodies with the clinical features of Graves’ ophthalmopathy. Clin Endocrinol 2000; 52:267–271. 20. DeGroot LJ, Mangklabruks A, McCormick M. Comparison of RA 131 I treatment protocols for Graves’ disease. J Endocrinol Invest 1990; 13:111–118. 21. Barth A, Probst P, Bu¨rgi H. Identification of a subgroup of Graves’ disease patients at higher risk for severe ophthalmopathy after radioiodine. J Endocrinol Invest 1991; 14:209–212. 22. Prummel MF, Wiersinga WM, Mourits MPh, Koornneef L, Berghout A, van der Gaag R. Effect of abnormal thyroid function on the severity of Graves’ ophthalmopathy. Arch Intern Med 1990; 150:1098–1101. 23. Prummel MF, Wiersinga WM, Mourits MPh, Koornneef L, Berghout A, van der Gaag R. Amelioration of eye changes of Graves’ ophthalmopathy by achieving euthyroidism. Acta Endocrinol (Copenh) 1989; 121(suppl 2):185–189. 24. Karlsson FA, Dahlberg PA, Jansson R, Westermark K, Enoksson P. Importance of TSH receptor activation in the development of severe endocrine ophthalmopathy. Acta Endocrinol (Copenh) 1989; 121(suppl 2):132–141.

26 Cigarette Smoking and Thyroid Eye Disease LUIGI BARTALENA University of Insubria, Varese, Italy CLAUDIO MARCOCCI and ALDO PINCHERA University of Pisa, Pisa, Italy

I.

INTRODUCTION

Graves’ ophthalmopathy represents the most frequent extrathyroidal manifestation of Graves’ disease, but it may more rarely also occur in patients with hypothyroid Hashimoto’s thyroiditis or in subjects with no evidence of hyperthyroidism (euthyroid Graves’ disease) (1). In most cases ocular involvement is mild and nonprogressive, but 3–5% of patients have severe expressions of the disease that require aggressive treatment, such as high-dose systemic glucocorticoids, orbital radiotherapy, or orbital decompression (2). Pathogenesis of the ophthalmopathy is incompletely understood, but it is widely accepted that the disease has an autoimmune origin (3). Autoreactive T lymphocytes recognizing one or more antigens in common to the thyroid and the orbit might infiltrate the orbital space; this process would be facilitated by adhesion molecules (4), the expression of which is enhanced by cytokines (5,6). After recognition of the shared antigen(s), T lymphocytes would produce cytokines responsible for amplification of the autoimmune process (7). Relevant actions of cytokines in the orbital disorder include induction of expression of major histocompatibility complex (HLA) class II molecules (8) and heat shock protein-72 (HSP-72), which are important for T-cell recruitment (4); stimulation of orbital fibroblasts to proliferate (9) and to secrete glycosaminoglycans (10), which are responsible for periorbital and eye muscle swelling and proptosis; protection of infiltrating T lymphocytes from apoptosis (11), thus favoring perpetuation of the immune process. The nature of the antigen(s) shared by the thyroid and the orbit remains to be established, 251

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but the thyrotropin receptor (TSH-R), the autoantigen involved in the pathogenesis of Graves’ hyperthyroidism, is probably involved (1). Another less likely possibility is that eye muscle antigens are primarily responsible for triggering the autoimmune process (12). Independent of the pathogenic mechanism, an unanswered question is why only 30– 40% of Graves’ patients develop clinically evident ophthalmopathy, and only a minority have severe eye disease. One possible explanation is that, on an as yet poorly defined genetic background (13,14), environmental factors provide an important contribution to the occurrence and/or progression of eye disease. Extrinsic variables possibly affecting the development of the ophthalmopathy include severity of hyperthyroidism (15), high serum TSH-R autoantibody concentration (16), untreated hypothyroidism (17,18). Undoubtedly, cigarette smoking constitutes a well-established and characterized risk factor for the occurrence and progression of eye disease (19), as outlined below. Tobacco smoke is composed of as many as several thousands active compounds, most of which are toxic on either acute or long-term exposure. Many tobacco-derived substances are also poisonous to ocular structures, affecting the eye through ischemic or oxidative mechanisms (20). A strong association has been observed between smoking and several common eye diseases, including glaucoma, cataract, age-related macular degeneration, and retinal ischemia (21). In these disorders, smoking appears to be an independent risk factor with dose-related effects (21). Clinical studies investigating the relation between cigarette smoking and Graves’ ophthalmopathy, and the putative mechanisms involved, are analyzed in the following sections. II. PREVALENCE OF SMOKING IN PATIENTS WITH GRAVES’ OPHTHALMOPATHY The idea that cigarette smoking affects Graves’ ophthalmopathy is relatively recent. In a small series of patients with Graves’ disease, it was originally shown that the number of smokers was considerably higher in patients with ophthalmopathy (83%) (10,12) than in those without ophthalmopathy (46%) (11,24), as was total tobacco consumption (22). In a subsequent large survey of the smoking habits of 1730 women with thyroid disorders or normal controls, the prevalence of smokers among patients with Graves’ disease (48%) was much higher than that in patients with nontoxic goiter, toxic nodular goiter, Hashimoto’s thyroiditis, or normal controls: in all the latter groups the prevalence of smokers was around 30% (23) (Table 1). The prevalence of smokers was significantly higher in Graves’ patients with clinically relevant eye disease (64%) (Table 1); in addition, heavy smokers were more frequently found in the subgroup with more severe ophthalmopathy (23). These findings were subsequently confirmed by numerous papers (1,19; Table 2). In an English study, 53 of 85 patients with Graves’ ophthalmopathy (62%) were smokers (24). In this study the prevalence of smokers among Graves’ patients without ocular involvement did not differ from that found in control subjects (24). Among 83 Hungarian patients, 36 of 38 with ophthalmopathy (95%) were smokers, while only 10 of 45 without ophthalmopathy (40%) smoked (25). A consecutive-entry case–control study showed that cigarette smoking greatly increased the risk of Graves’ ophthalmopathy (odds ratio, 7.7) (26). In a prospective study of 253 patients with a recent onset of Graves’ hyperthyroidism, cigarette smoking was recently associated with a 1.3-fold increased incidence of clinically relevant ophthalmopathy and 2.6-fold and 3.1-fold increases of proptosis and diplopia, respectively (27). These findings are in agreement with another report showing that the

Smoking and Graves’ Ophthalmopathy

253

Table 1 Prevalence of Smokers Among Women with Various Thyroid Disorders Group Nontoxic goiter Toxic nodular goiter Hashimoto’s thyroiditis Graves’ disease without ophthalmopathy Graves’ disease with ophthalmopathy Normal controls

Number of subjects

Smokers

%

405 165 200 167 307 486

123 39 67 80 197 135

30 23 33 48* 64* 28

* p ⬍ 0.01 vs. all other groups; Graves’ disease with ophthalmopathy vs. Graves’ disease without ophthalmopathy, p ⬍ 0.05. Source: From Ref. 23.

risk of developing ophthalmopathy was 2.4-fold higher than that observed in patients who never smoked (28). In a study of 171 patients assigned to receive different forms of treatment of hyperthyroidism, developing or worsening of the ophthalmopathy was more likely to occur in smokers (19%) than in nonsmokers (8%), independent of the type of treatment of hyperthyroidism (29). The current number of daily cigarettes, rather than lifetime cigarette consumption, appears to be an independent risk factor for the occurrence of Graves’ ophthalmopathy (27). In another study of 536 patients with Graves’ hyperthyroidism, cigarette smoking was strongly associated with ophthalmopathy and was a predictor for the presence of eye disease at diagnosis (30). This is in agreement with a report showing that among Graves’ patients with mild ophthalmopathy there were slightly more patients with a history of smoking and, more important, more current smokers compared to Graves’ patients without the ophthalmopathy (31). Ethnic factors may affect the influence of smoking on Graves’ ophthalmopathy, since in one study the prevalence of smokers was higher in white patients than in Asian Table 2 Prevalence of Smokers Among Patients with Graves’ Ophthalmopathy Author

Year

Hagg Bartalena Shine Balazs Tellez Winsa Tallstedt Prummel Pfeilschifter Hofbauer Mann Salvi Allahabadia Total

1987 1989 1990 1990 1992 1993 1993 1993 1996 1997 1999 2000 2000

Number of patients

Number of smokers

%

Reference

12 307 85 38 52 62 24 100 52 27 50 72 216 1097

10 196 53 36 23 30 19 81 23 18 35 31 102 657

83 64 62 95 44 48 79 81 44 67 70 43 47 60

22 23 24 25 28 31 29 26 27 51 37 53 30

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patients (42% vs. 7.7%) (28). A contribution of genetic factors was suggested in view of the observation that the majority of Hungarian patients who smoked and had a relevant ocular involvement also were HLA-B8 and/or DR positive (25). In summary, an increased number of smokers is found among patients with Graves’ ophthalmopathy, with an overall prevalence of smokers of about 60% (Table 2). Furthermore, the degree of smoking seems to influence the severity of eye disease. Finally, current smoking seems to be more important than lifetime tobacco consumption for the occurrence or progression of ophthalmopathy. III. EFFECT OF SMOKING ON THE COURSE OF GRAVES’ OPHTHALMOPATHY AND ITS TREATMENT The relationship between treatment of Graves’ hyperthyroidism and the course of ophthalmopathy is not fully understood (1). Antithyroid drugs usually do not cause substantial changes in the ophthalmopathy (32). Likewise, thyroidectomy does not seem to be associated with the subsequent occurrence or progression of eye disease (33). However, radioiodine therapy may cause, in about 15% of cases, the exacerbation of preexisting ophthalmopathy or, more rarely, the occurrence of new ophthalmopathy (34). This undue course of eye disease can, however, be prevented by a relatively short course of mid-dose glucocorticoids (35). We recently investigated whether cigarette smoking may affect the course of the ophthalmopathy following radioiodine therapy. In a large cohort of patients with nonsevere ophthalmopathy, progression of eye disease after radioiodine therapy was observed in only 4 of 68 nonsmokers (6%) and in 19 of 82 smokers (23%), while improvement of pre-existing ophthalmopathy with the concomitant glucocorticoid treatment occurred in 37 of 58 nonsmokers (64%) and in only 13 of 87 smokers (15%) (36). This suggests that in patients with nonsevere Graves’ ophthalmopathy, smoking is an important risk factor for progression of ocular disease after radioiodine therapy and decreases the efficacy of glucocorticoid therapy. In a retrospective study of 150 consecutive patients with severe Graves’ ophthalmopathy who underwent orbital radiotherapy combined with high-dose systemic glucocorticoids, 61 of 65 nonsmokers (94%) showed a favorable outcome of treatment, whereas among smokers responders to treatment were 58 of 85 (68%) (36) (Table 3). The degree of smoking also appeared to influence the outcome of treatment, since 33 of the 58 smokers who responded to therapy (57%) and only 5 of 27 smokers who did not respond to treatment (18%) were light smokers (36). Thus, it appears that current cigarette smoking con-

Table 3 Cigarette Smoking and Treatment Outcome in Patients with Severe Graves’ Ophthalmopathy Submitted to Combined Treatment with Orbital Radiotherapy and High-Dose Systemic Glucocorticoids Smoking behavior Smokers (n ⫽ 85) Nonsmokers (n ⫽ 65) Total (n ⫽ 150) Source: From Ref. 36.

Number of responders 58 61 119

% 68 94

Number of nonresponders 27 4 31

% 32 6


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tributes to decrease the effectiveness of medical and radiotherapeutic management of severe Graves’ ophthalmopathy. Similar results were reported in another study of 50 patients with Graves’ ophthalmopathy who underwent the same combined treatment as above: improvement of ocular signs and symptoms, especially soft tissue changes and ocular motility, was greater in smokers than in nonsmokers (37).

IV.

MECHANISM OF ACTION OF SMOKING ON GRAVES’ OPHTHALMOPATHY

The mechanism of action of smoking on Graves’ ophthalmopathy is largely unknown (38). Direct irritative actions on the eyes are likely. Cigarette smoking is highly irritating to the conjunctival mucosa. This may contribute to the inflammatory changes involving soft tissues responsible for burning, tearing, grittiness, and conjunctival hyperemia, but cannot explain the increased volume of extraocular muscles and retrobulbar fibroadipose tissue. Since stressful events seem to play some role in the pathogenesis of Graves’ disease (39), and stress is associated with an increased desire to smoke (40), cigarette smoking might simply be an epiphenomenon, while other tobacco-unrelated factors might bear the true responsibility for the occurrence or progression of the ophthalmopathy. On the other hand, cigarette smoking might exert its effect on Graves’ ophthalmopathy by influencing the immune surveillance and immune reactions effectively involved in the pathogenesis of the disease. For example, it has been suggested that smoking might alter the structure of the TSH-R to make it more immunogenic, hamper the restoration of tolerance to autoantigen(s) shared by the thyroid and the orbit, or sensitize the orbital tissue to whatever substance or antibody capable of triggering the ophthalmopathy (41). Because smoking is associated with increased serum thyroglobulin (Tg) levels (42), an increase in serum anti-Tg autoantibodies might play a role in the pathogenesis of the eye disease, in view of the reported homology between Tg and acetylcholinesterase, which is particularly abundant in the nerve–nerve and nerve–muscle junctions of the extraocular muscles (43). The relevance of this homology has, however, been questioned (44). As discussed in the Introduction to this chapter, cytokines play an important role in the pathogenesis of Graves’ ophthalmopathy (1). Smoking might influence autocrine and paracrine actions mediated by cytokines, since it has been reported that smokinginduced hypoxia in the orbital space is associated with an increased release of cytokines (45). Cigarette smoking constituents were shown in vitro to increase the expression of HLA-DR when added to orbital fibroblasts culture in combination with interferon-γ (46). In addition, interleukin-1 (IL-1) production is stimulated in vitro by tobacco glycoprotein (47). An increased cytokine release induced by smoking may also occur in endothelial cells (48,49), leading to increased expression of adhesion molecules (5,6). In cultured orbital fibroblasts, IL-1-induced stimulation of glycosaminoglycan synthesis was inhibited by cytokine antagonists, such as soluble IL-1 receptor antagonist (IL-1ra) (50). Orbital fibroblasts from patients with Graves’ ophthalmopathy express lower levels of IL-1ra than orbital fibroblasts from control subjects (51). In vivo it was reported that patients with ophthalmopathy who smoke had lower serum IL-1ra concentration than nonsmokers, and a lower surge after orbital radiotherapy, which was associated with a lack of response to treatment (52). This relationship between cigarette smoking and serum IL-1ra levels is, however, controversial, since it was not found in two independent series of Graves’ patients (53,54).

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In view of the role of cytokines in the pathogenesis of ocular changes of Graves’ ophthalmopathy, a novel approach to the management of the ophthalmopathy based on the use of cytokine antagonists might be envisaged (55), but clinical trials similar, for example, to those being carried out in the field of rheumatoid arthritis are lacking for Graves’ ophthalmopathy. In summary, it is conceivable that cigarette smoking, which is associated with numerous abnormalities of the immune system (56), may affect the immune process in the orbital tissue. Other, as yet unexplained, mechanisms may, however, contribute to the effect of smoking on the ophthalmopathy. V.

CONCLUSIONS

The relationship between cigarette smoking and Graves’ ophthalmopathy appears to be well established. In particular, the prevalence of smokers is higher in Graves’ patients with the ophthalmopathy (60%) than in those without the ophthalmopathy or in those with other thyroid disorders. Cigarette smoking tends to be associated with a greater severity of the disease. In addition, smoking negatively affects the course of nonsevere ophthalmopathy after radioiodine therapy and reduces the effectiveness of treatment of severe ophthalmopathy with orbital radiotherapy and high-dose systemic glucocorticoids. The mechanisms by which cigarette smoking affects Graves’ ophthalmopathy are not completely understood, but it is likely that smoking may influence the immune reactions involved in the pathogenesis of the disease. The above considerations suggest that both the endocrinologist and the ophthalmologist should strongly advise the patient to stop smoking immediately. The possible use of drugs, such as bupropion, to help smoking withdrawal will have to be evaluated in appropriately designed controlled studies. In a recent editorial, Keltner stated that he does not operate on Graves’ patients for residual strabismus unless they have stopped smoking for at least 1 month prior to surgery (57). Such strong pressure on the patient should also probably be applied before nonsurgical treatments of the ophthalmopathy, such as orbital radiotherapy and high-dose glucocorticoids. Whether refraining from smoking favorably influences the course of the disease remains to be definitely proven by prospective studies, but some data seem to indicate that this is the case (27). ACKNOWLEDGMENTS This work was supported by grants from the University of Insubria, Varese (Fondi d’Ateneo) and from the Ministero dell’Universita` e della Ricerca Scientifica e Tecnologica (MURST), Rome (project: ‘‘New Models for the Diagnosis and Treatment of Graves’ Ophthalmopathy’’) to Dr. Bartalena. REFERENCES 1. Bartalena L, Pinchera A, Marcocci C. Management of Graves’ ophthalmopathy: reality and perspectives. Endocr Rev 2000; 21:168–199. 2. Bartalena L, Marcocci C, Pinchera A. Treating severe Graves’ ophthalmopathy. Baillieres Clin Endocrinol Metab 1997; 11:521–526. 3. Burch HB, Wartofsky L. Graves’ ophthalmopathy: current concepts regarding pathogenesis and management. Endocr Rev 1993; 14:747–793.


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4. Heufelder AE. Retro-orbital autoimmunity. Baillieres Clin Endocrinol Metab 1997; 11:499– 520. 5. Heufelder AE, Scriba PC. Characterization of adhesion receptors on cultured microvascular endothelial cells derived from the retroorbital connective tissue of patients with Graves’ ophthalmopathy. Eur J Endocrinol 1996; 134:51–60. 6. Pappa A, Calder V, Fells P, Lightman S. Adhesion molecules expression in vivo on extraocular muscles (EOM) in thyroid-associated ophthalmopathy. Clin Exp Immunol 1997:362–369. 7. Wiersinga WM. Graves’ ophthalmopathy. Thyroid Int 1997; 3:1–15. 8. Heufelder AE, Smith TJ, Gorman CA, Bahn RS. Increased induction of HLA-DR by interferon-γ in cultured retroocular fibroblasts derived from patients with Graves’ ophthalmopathy and pretibial myxedema. J Clin Endocrinol Metab 1991; 73:307–313. 9. Heufelder AE. Pathogenesis of Graves’ ophthalmopathy: recent controversies and progress. Eur J Endocrinol 1995; 132:532–541. 10. Smith TJ, Bahn RS, Gorman CA, Cheavens M. Stimulation of glycosaminoglycan accumulation by interferon-γ in cultured retroocular fibroblasts. J Clin Endocrinol Metab 1991; 72: 1169–1171. 11. Mohacsi A, Trieb K, Anderl H, Grubeck-Loebenstein B. Retrobulbar fibroblasts from patients with Graves’ ophthalmopathy induce down-regulation of APO-1 in T-lymphocytes and protect T cells from apoptosis during coculture. Int Arch Allergy Immunol 1996; 109:327–333. 12. Gunji K, Kubota S, Swanson J, Kiljanski J, Bednarczuk T, Wengrowicz S, Salvi M, Wall JR. Role of the eye muscles in thyroid eye disease: identification of the principal autoantigens. Thyroid 1998; 8:175–179. 13. Tomer Y, Davies TF. The genetic susceptibility to Graves’ disease. Baillieres Clin Endocrinol Metab 1997; 11:431–450. 14. Farid NR, Balazs C. The genetics of thyroid associated ophthalmopathy. Thyroid 1998; 8: 407–409. 15. Tallstedt L, Lundell G, Torring O, Wallin G, Ljumggren J-C, Blomgren H, Taube A, and the Thyroid Study Group. Occurrence of ophthalmopathy after treatment for Graves’ hyperthyroidism. N Engl J Med 1992; 326:1733–1738. 16. Gerding MN, van der Meer JWC, Broenink M, Bakker O, Wiersinga WM, Prummel MF. Association of thyrotrophin receptor antibodies with the clinical features of Graves’ ophthalmopathy. Clin Endocrinol (Oxf ) 2000; 52:267–271. 17. Karlsson AF, Westermark K, Dahlberg PA, Jansson R, Enoksson P. Ophthalmopathy and thyroid stimulation. Lancet 1989; 2:691. 18. Kung AWC, Yau CC, Cheng A. The incidence of ophthalmopathy after radioiodine therapy for Graves’ disease: prognostic factors and the role of methimazole. J Clin Endocrinol Metab 1994; 79:542–546. 19. Bartalena L, Bogazzi F, Tanda ML, Manetti L, Dell’Unto E, Martino E. Cigarette smoking and the thyroid. Eur J Endocrinol 1995; 133:507–512. 20. Solberg Y, Rosner M, Belkin M. The association between cigarette smoking and ocular diseases. Surv Ophthalmol 1998; 42:535–547. 21. Cheng AC, Wang CP, Leung AT, Chua JK, Fan DS, Lam DS. The association between cigarette smoking and ocular diseases. Hong Kong Med J 2000; 6:195–202. 22. Hagg E, Asplund K. Is endocrine ophthalmopathy related to smoking? Br Med J 1987; 259: 634–635. 23. Bartalena L, Martino E, Marcocci C, Bogazzi F, Panicucci M, Velluzzi F, Loviselli A, Pinchera A. More on smoking habits and Graves’ ophthalmopathy. J Endocrinol Invest 1989; 12:733– 737. 24. Shine B, Fells P, Edwards OM, Weetman AP. Association between Graves’ ophthalmopathy and smoking. Lancet 1990; 335:1261–1263. 25. Balazs C, Stenszky V, Farid NR. Association between Graves’ ophthalmopathy and smoking. Lancet 1990; 335:754.

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26. Prummel MF, Wiersinga WM. Smoking and risk of Graves’ disease. JAMA 1993; 269:479– 482. 27. Pfeilschifter J, Ziegler R. Smoking and endocrine ophthalmopathy: impact of smoking severity and current vs lifetime cigarette consumption. Clin Endocrinol (Oxf ) 1996; 45:477–481. 28. Tellez M, Cooper J, Edmonds C. Graves’ ophthalmopathy in relation to cigarette smoking and ethnic origin. Clin Endocrinol (Oxf ) 36:291–294. 29. Tallstedt L, Lundell G, Taube A. Graves’ ophthalmopathy and tobacco smoking. Acta Endocrinol (Copenh) 1993; 129:147–150. 30. Allahabadia A, Daykin J, Holder RL, Sheppard MC, Gough SCL, Franklyn JA. Age and gender predict the outcome of treatment for Graves’ hyperthyroidism. J Clin Endocrinol Metab 2000; 85:1038–1042. 31. Winsa B, Mandahl A, Karlsson FA. Graves’ disease, endocrine ophthalmopathy, and smoking. Acta Endocrinol (Copenh) 1993; 128:156–160. 32. Wiersinga WM, Prummel MF. An evidence-based approach to the treatment of Graves’ ophthalmopathy. Endocrinol Metabol Clin North Am 2000; 29:297–319. 33. Marcocci C, Bruno-Bossio G, Manetti L, Tanda ML, Miccoli P, Iacconi P, Bartolomei MP, Nardi M, Pinchera A, Bartalena L. The course of Graves’ ophthalmopathy is not influenced by near-total thyroidectomy: a case–control study. Clin Endocrinol (Oxf ) 1999; 51:503–506. 34. Bartalena L, Marcocci C, Bogazzi F, Manetti L, Tanda ML, Dell’Unto ML, Bruno-Bossio G, Nardi M, Bartolomei MP, Lepri A, Rossi G, Martino E, Pinchera A. Relation between therapy for hyperthyroidism and the course of Graves’ ophthalmopathy. N Engl J Med 1998; 338:73– 78. 35. Bartalena L, Marcocci C, Bogazzi F, Panicucci M, Lepri A, Pinchera A. Use of corticosteroids to prevent progression of Graves’ ophthalmopathy after radioiodine therapy for hyperthyroidism. N Engl J Med 1989; 321:1349–1352. 36. Bartalena L, Marcocci C, Tanda ML, Manetti L, Dell’Unto ML, Bartolomei MP, Nardi M, Martino E, Pinchera A. Cigarette smoking and treatment outcomes in Graves’ ophthalmopathy. Ann Intern Med 1998; 129:632–635. 37. Mann K. Risk of smoking in thyroid-associated orbitopathy. Exp Clin Endocrinol Diabetes 1999; 107(Suppl 5):S164–S166. 38. Martino E, Bogazzi F, Pinchera A, Bartalena L. Cigarette smoking and thyroid autoimmunity. In: Pe`ter F, Wiersinga W, Hostalek U, eds. The Thyroid and Environment. Stuttgart: Schattauer, 2000:145–154. 39. Winsa B, Adami H-O, Bergstrom R, Gamstedt A, Dahlberg PA, Adamson U, Jansson R, Karlsson A. Stressful events and Graves’ disease. Lancet 1991; 338:1475–1479. 40. Perkins KA, Grobe JE. Increased desire to smoke during acute stress. Br J Addiction 1992; 87:1037–1040. 41. Utiger RD. Cigarette smoking and the thyroid. N Engl J Med 1995; 333:1001–1002. 42. Borup Christensen S, Ericcson U-B, Janzon L, Tibblin S, Melander A. Influence of cigarette smoking on goiter formation, thyroglobulin, and thyroid hormone levels in women. J Clin Endocrinol Metab 1984; 58:615–618. 43. Ludgate M, Swillens S, Mercken L, Vassart G. Homology between thyroglobulin and acetylcholinesterase: an explanation for the pathogenesis of Graves’ ophthalmopathy? Lancet 1986; 2:219–220. 44. Weetman AP, Tse CK, Randall WR, Tsim KWK, Barnard EA. Acetylcholinesterase antibodies and thyroid autoimmunity. Clin Exp Immunol 1988; 71:96–99. 45. Metcalfe RA, Weetman AP. Stimulation of extraocular muscle fibroblasts by cytokines and hypoxia: possible role in thyroid-associated ophthalmopathy. Clin Endocrinol (Oxf ) 1994; 40: 67–72. 46. Mack WP, Stasior GO, Cao HJ, Stasior OG, Smith TJ. The effect of cigarette smoke on the expression of HLA-DR in orbital fibroblasts derived from patients with Graves’ ophthalmopathy. Ophthal Plast Reconstr Surg 1999; 15:260–271.


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47. Francus T, Manzo G, Camki M, Thompson LC, Szabo P. Two peaks of interleukin-1 expression in human leukocyte cultures with tobacco glycoprotein. J Exp Med 1989; 170:327–332. 48. Ala Y, Palluy O, Favero C, Modat G, Dormand I. Hypoxia/reoxygenation stimulates endothelial cells to promote interleukin-1 and interleukin-6 production. Effects of free radical scavengers. Agents Action 1992; 37:134–139. 49. Shreeniwas R, Koga S, Karakurum M, Pinsky D, Kaiser E, Brett J. Hypoxia-mediated induction of endothelial cells interleukin-1. J Clin Invest 1992; 90:2333–2339. 50. Tan GH, Duttyon CM, Bahn RS. Interleukin-1 (IL-1) receptor antagonist and soluble IL-1 receptor inhibit IL-1 induced glycosaminoglycan production in cultured human orbital fibroblasts from patients with Graves’ ophthalmopathy. J Clin Endocrinol Metab 1996; 81:449– 452. 51. Muhlberg T, Heberling H-J, Joba W, Schworm H-D, Heufelder AE. Detection and modulation of interleukin-1 receptor antagonist messenger ribonucleic acid and immunoreactivity in Graves’ orbital fibroblasts. Ophthalmol Vis Sci 1997; 38:1018–1028. 52. Hofbauer LC, Muhlberg T, Konig A, Heufelder G, Schworm H-D, Heufelder AE. Soluble interleukin-1 receptor antagonist serum levels in smokers and nonsmokers with Graves’ ophthalmopathy undergoing orbital radiotherapy. J Clin Endocrinol Metab 1997; 82:2244–2247. 53. Bartalena L, Manetti L, Tanda ML, Dell’Unto E, Mazzi B, Rocchi R, Barbesino G, Pinchera A, Marcocci C. Soluble interleukin-1 receptor antagonist concentration in patients with Graves’ ophthalmopathy is neither related to cigarette smoking nor predictive of subsequent response to glucocorticoids. Clin Endocrinol (Oxf ) 2000; 52:647–650. 54. Salvi M, Pedrazzoni M, Girasole G, Giuliani N, Minelli R, Wall JR, Roti E. Serum concentrations of proinflammatory cytokines in Graves’ disease: effect of treatment, thyroid function, ophthalmopathy and cigarette smoking. Eur J Endocrinol 2000; 143:197–202. 55. Bartalena, Marcocci C, Pinchera A. Cytokine antagonists: new ideas for the management of Graves’ ophthalmopathy. J Clin Endocrinol Metab 1996; 81:446–448. 56. Editorial. Smoking and immunity. Lancet 1990; 335:1561–1562. 57. Keltner JL. Is Graves’ disease a preventable disease? Arch Ophthalmol 1998; 116:1196–1197.

27 Orbital Anatomy and Graves’ Disease JONATHAN J. DUTTON Atlantic Eye and Face Center, Cary, and University of North Carolina, Chapel Hill, North Carolina, U.S.A.

I.

INTRODUCTION

Understanding the orbital manifestations of Graves’ disease and its management demands a clear concept of orbital anatomy and physiology. Only against this background can we identify and characterize the pathological changes associated with this disorder. The development of more appropriate surgical techniques also requires a comprehensive knowledge of the structural relationships among the numerous anatomical systems crowded into this limited space. The human orbit is a small cone-shaped cavity, with the apex pointing posteriorly. Within this space are crowded a complex array of tightly packed structures serving visual function (1). Lobules of orbital fat and connective tissue fascia fill the spaces between muscles, nerves, and vascular elements, providing a cushion that protects these delicate elements from injury during ocular movement. The entire complex is bound together into a functional unit whose complexity and precision are unmatched elsewhere in the vertebrate body (2). II. OSTEOLOGY OF THE ORBIT The bony orbit forms from mesenchyme, and individual bones develop from a complex series of primary or secondary ossifications. In the adult, the bony orbit encloses a volume of about 30 cm3. It is composed of seven bones, simplified from a complex of dermal and endochondral elements of earlier vertebrates (Fig. 1). Except for a series of canals, fissures, and foramina that communicate with extraorbital compartments, the orbit is closed on all sides with a broad opening anteriorly. This explains the characteristic development of 261

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Figure 1 Bony anatomy of the orbit in frontal view. (From Ref. 2.)

proptosis as a clinical sign even with minimal enlargement of the fat compartment or extraocular muscles in Graves’ disease. A.

Orbital Roof

The orbital roof is composed of the orbital plate of the frontal bone with a small contribution from the lesser wing of the sphenoid at the apex. It is a thin lamina separating the orbit anteriorly from the frontal sinus, and posteriorly from the anterior cranial fossa. The roof slopes backward and downward toward the apex, where it ends at the optic canal and superior orbital fissure. The optic canal is an oval opening near the orbital apex where it measures 5–6 mm in diameter. Although the orbital roof is normally of little concern in Graves’ disease, some authors in the past have advocated a four-wall decompression in which this wall is removed. B.

Lateral Orbital Wall

The lateral wall of the orbit is formed posteriorly by the greater wing of the sphenoid bone, and anteriorly by the zygomatic process of the frontal bone and the orbital process of the zygomatic bone. It lies at a nearly 45-degree angle to the midsagittal plane. The lateral wall is bounded below by the inferior orbital fissure, and medially by the superior orbital fissure. Behind the thick lateral orbital rim, the wall becomes quite thin where the zygomatic bone joins the greater sphenoid wing at a vertical suture line. The convoluted frontozygomatic suture line runs approximately horizontally and crosses the superotemporal rim near the lacrimal gland fossa. About halfway along the lateral wall, in the sphenoid wing near the frontosphenoid suture, is a small canal carrying an anastomotic branch between the lacrimal and meningeal arteries. In some cases of orbital decompression where

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there is severe orbital congestion, it may be useful to remove the lateral wall to allow easier access to the medial wall. C.

Orbital Floor

The floor is the shortest of the orbital walls, extending back only about 35–40 mm from the inferior rim. The orbital floor is composed primarily of the maxillary bone, with the zygomatic bone forming the anterolateral portion, and the palatine bone lying at the posterior extent of the floor. Its surface forms a triangular segment extending from the maxillary–ethmoid buttress, horizontally to the inferior orbital fissure, and from the orbital rim back to the posterior wall of the maxillary sinus. The floor ends at the posterior limit of the maxillary sinus and, therefore, does not extend to the orbital apex. Despite its thinness, the floor is strengthened by the infraorbital canal, which runs through it near its center, and by the presence of one or more trabeculae in the roof of the maxillary sinus. The infraorbital groove begins at the inferior orbital fissure and runs forward in the maxillary bone. About 15 mm from the orbital rim this groove usually becomes bridged over with a thin lamina of bone to form the infraorbital canal. Within this canal runs the maxillary division of the trigeminal nerve with the maxillary artery. These exit just below the central orbital rim at the infraorbital foramen. Surgery on the floor during orbital decompression must pay special attention to these structures to avoid injury. Separating the floor from the lateral orbital wall is the inferior orbital fissure. This opening is approximately 20 mm in length, and runs in an anterolateral to posteromedial direction. Multiple branches from the inferior ophthalmic vein pass through this opening to communicate with the pterygoid venous plexus. The smooth sympathetic muscle of Mu¨ller bridges over the inferior fissure, surrounding these penetrating venules. In Graves’ disease these smooth muscle fibers may become thickened as a spillover of the immune process, and can possibly result in venous outflow obstruction and orbital congestion. During orbital decompression, the orbital floor is removed from the inferior rim to the posterior extent of the maxillary sinus. Many surgeons leave some bone around the infraorbital canal to protect the nerve and inhibit hypoglobus. It is important to leave the maxillary buttress intact inferomedially to prevent the globe from displacing downward and inward. D. Medial Orbital Wall The medial walls of the orbit are approximately parallel to each other and to the midsagittal plane. The medial wall is composed largely of the lamina papyracea of the ethmoid bone. This thin plate is exceptionally fragile, measuring only 0.2–0.4 mm in thickness, and separates the orbit from air cells of the ethmoid sinus labyrinth. Anterior to the ethmoid is the lacrimal bone, a thin plate containing the posterior lacrimal crest, and forming the posterior half of the lacrimal sac fossa. In the midportion of the fossa, the lacrimal bone joins the orbital process of the maxillary bone. The latter is a thick bone that forms the medial orbital rim. Within the frontoethmoid suture line in the superomedial orbit are two openings; the anterior and posterior ethmoidal foramina. The former usually lies 20–25 mm behind the anterior lacrimal crest, and the latter 32–35 mm behind the anterior crest and 5–10 mm anterior to the optic canal. These foramina transmit branches of the ophthalmic artery and nasociliary nerve into the ethmoid sinus and nose and mark the upper safe limit for removing the medial wall in orbital decompression. The position of these foramina marks

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the approximate level of the roof of the ethmoid labyrinth, and the floor of the anterior cranial fossa at the cribriform plate. III. CONNECTIVE TISSUE SYSTEMS In the human an extensive system of connective tissue forms a framework for compartmentalization and support of orbital structures (3–6). It is essential for maintaining appropriate anatomical relationships between structural components, and for allowing precise and coordinated ocular movements. Some connective tissue septa are aligned with directions of force that resist displacement of extraocular muscles during contraction. Others suspend and support delicate orbital vascular and neural elements. The essential elements of this system include the periorbita, the orbital septal systems, and Tenon’s capsule (Fig. 2). Contraction and fibrosis of these septae are a major cause of the restrictive myopathy and eyelid retraction seen in Graves’ eye disease. A.

Periorbita

The orbit is lined with periosteum that is loosely adherent to the underlying orbital bones. Applied to the inner surface of the periosteum are multiple layers of orbital connective tissue that are continuous with the transorbital septal systems (2). Together, this complex layer is known as the periorbita. Within the orbit, the periorbita serves to support the extensive septal systems and to stabilize anatomical structures. It forms the boundaries of the entire orbital compartment. At the orbital rim, periorbita separates into its component layers. Periosteum continues over the rims and remains in contact with the outer table of the cranial bones. The inner layers of the connective tissue system separate at the arcus marginalis and extend into

Figure 2 Orbital connective tissue fascial systems in cross section through the midorbit. (From Ref. 2.)

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the eyelids as the orbital septum. Thus, the septum represents the anteriormost boundary of the orbit. As the orbital fat volume increases in Graves’ disease, the septum is not capable of retaining it, resulting in significant prolapse of orbital fat into the eyelids. B.

Orbital Septal Systems

Suspended from the periorbita and forming a complex radial and circumferential web of interconnecting slings are the connective tissue septa (6). These septa form fine capsules around the intraconal and extraconal fat lobules. They also surround the extraocular muscles, optic nerve, and neurovascular elements, and suspend these structures to the adjacent orbital walls. The fascial slings provide support and maintain constant spatial relationships between these anatomical structures during ocular movements. Fibrosis along these septa is responsible for transmission of restrictive forces in Graves’ disease. Encircling septa around the optic nerve and superior ophthalmic vein may also serve to confine edema, resulting in compressive optic neuropathy and orbital congestion. The anterior fascial system of the orbit is primarily related to support of the globe, anterior orbital structures such as the lacrimal gland and superior oblique tendon, and the eyelids. It consists of a number of well-developed condensations and ligaments, as well as a more diffuse system of fibrous septa: the medial and lateral check ligaments, Lockwood’s inferior ligament, Whitnall’s superior suspensory ligament, the lacrimal ligaments, the intermuscular septum. These structures coordinate movements between the globe and eyelids, and suspend the globe so that gaze movements occur around stable axes of rotation. In the midorbit, the connective tissue system is best developed. It forms a welldefined sling and suspensory complex associated with each of the extraocular muscles. Here it serves to maintain muscle alignment, minimize vector shifts during eye movement, and reduce side-slip over the rotating globe. IV.

MUSCLES OF OCULAR MOTILITY

Within the orbital space are a number of structures whose function is to provide support, movement, and sensory innervation to the globe (7,8). The eye is an approximate sphere measuring about 24 mm in diameter and is situated in the anterior one-half of the orbit. Attached to it are the six striated extraocular muscles (Fig. 3). The four rectus muscles arise posteriorly from the annulus of Zinn, a fibrous band continuous with periorbita and dura at the optic foramen. The annulus surrounds the optic foramen and the central onethird of the superior orbital fissure through which neurovascular structures pass from the middle cranial fossa into the intraconal orbital space. The muscles run forward with only a thin layer of extraconal fat separating them from periorbita along the orbital walls. The superior oblique muscle arises above the annulus, just superior and medial to the optic foramen. It runs forward along the superomedial orbital wall to the cartilagenous trochlea through which its tendon slides before turning sharply laterally to insert on the superoposterior aspect of the globe (9). Removal of orbital fat from the superomedial orbit can injure the trochlea, resulting in superior oblique muscle dysfunction. The inferior oblique muscle arises anteriorly from a small depression just below and lateral to the lacrimal sac fossa. It passes laterally and slightly backward to insert on the inferoposterior surface of the globe near the macula. Along its course, the sheath of the inferior oblique muscle joins that of the inferior rectus muscle and Tenon’s capsule just behind the orbital rim to form Lockwood’s inferior suspensory ligament. Slips of this

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Figure 3 Extraocular muscles of ocular motility in frontal view. (From Ref. 2.)

structure pass to periosteum of the lateral orbital wall, and medially to join the posterior crus of the medial canthal tendon. The capsulopalpebral fascia extends anteriorly from this ligament to the inferior tarsal plate. Because of the proptosis associated with Graves’ disease, the inferior oblique muscle and suspensory complex are displaced forward, sometimes to or even anterior to the inferior orbital rim. During orbital decompression and lower eyelid blepharoplasty procedures, care must be exercised to avoid injury to these structures.

Figure 4 Motor nerves of the orbit. (From Ref. 2.)

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The levator superioris palpebrae muscle originates from the annulus of Zinn and lesser sphenoid wing. It runs forward along the orbital roof in close approximation to the superior rectus muscle. Fine check ligaments interconnect the levator to the superior rectus, as well as to periosteum of the frontal bone. Near the orbital rim fine suspensory ligaments extend from the levator sheath to the superior conjunctival fornix (2). In addition, at about this point, a horizontal condensation is seen within the muscle sheath forming prominent transverse ligament of Whitnall (10,11) (Fig. 4). Anterior to Whitnall’s ligament, the levator muscle passes into a thin fibrous aponeurosis, which turns inferiorly, and fans out into the eyelid. It inserts onto the inferior two-thirds of anterior tarsal face. Medially and laterally, the aponeurosis joins the canthal tendons via extensions known as the ‘‘horns.’’ The levator muscle is unusually sensitive to any superior orbital disease, such as mass lesions or inflammation, resulting in upper eyelid ptosis. The latter is, therefore, a frequent early sign of orbital pathological change. In Graves’ disease there can be marked fibrosis and contraction of these suspensory structures as well as of the suspensory ligaments of the superior conjunctival fornix. The result is the eyelid retraction so characteristic of this disease. V. MOTOR NERVES OF THE ORBIT The extraocular muscles are innervated by the third, fourth, and sixth cranial nerves (12) (Fig. 5). Just before entering the orbit through superior orbital fissure, the oculomotor nerve divides into a superior and inferior division. The superior branch innervates the superior rectus and levator muscles. The inferior branch sends fibers to the inferior rectus,

Figure 5 The levator aponeurosis and its relationship to the anterior connective tissue system. (From Ref. 2.)

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the medial rectus, and the inferior oblique muscles. These branches are applied to the inner surface of the muscles where they are cushioned and protected by the fibrous muscle sheaths. Running with the inferior division of the oculomotor nerve are parasympathetic fibers arising from the Edinger–Westphal subnucleus. These synapse in the ciliary ganglion just lateral and inferior to the optic nerve, 1.5–2 cm behind the globe. They progress via the short ciliary nerves to the ciliary body and iris sphincter. There is no redundancy to these nerves, and they are easily injured during orbital dissection, resulting in disturbances of pupillary function and accommodation. These neural structures may be injured during deep orbital surgery as with intraconal fat decompression. The trochlear nerve (IV) enters the extraconal space of the superior orbit through the superior orbital fissure above the annulus of Zinn. Here it crosses over the superior rectus and levator muscle complex and runs along the external surface of the superior oblique muscle before penetrating its substance in the posterior third of the orbit. In this position against the orbital roof, the trochlear nerve is easily damaged during blunt trauma, and from lateral displacement of periorbita during deep medial wall surgery. The abducens nerve (VI) enters the orbit through the superior orbital fissure and annulus of Zinn to enter the intraconal space. The nerve runs laterally to supply the lateral rectus muscle. VI.

SENSORY NERVES OF THE ORBIT

The optic nerve is technically not a sensory nerve, but a central nervous system tract arising from the retinal ganglion cells. Nasal fibers decussate in the optic chiasm. Fibers in the optic tracts continue backward and synapse in the lateral geniculate nuclei from where they radiate to the occipital cortex. The orbital portion of the nerve is somewhat redundant to allow for ocular movement. It is about 3 cm long, and takes a sinusoidal path from the globe, curving downward, then upward to the optic canal. In close approximation to the nerve are the ophthalmic artery near the orbital apex and superior ophthalmic vein in the midorbit. Both of these vessels lie superior to the nerve in most individuals. The central retinal artery runs along the inferolateral side of the nerve to enter the dura at about 1 cm behind the globe. The short and long posterior ciliary arteries lie close to the nerve for much of its length, and are highly convoluted and redundant near the globe. The optic nerve lies within the rectus muscle cone from the annulus of Zinn to the globe. As the extraocular muscles enlarge in Graves’ disease, the muscles can contact the nerve, resulting in compressive optic neuropathy. Bony orbital decompression allows the muscles to expand away from the nerve, and may therefore relieve the compression. Sensory innervation to the orbit is primarily from the ophthalmic division of the trigeminal nerve (V). The maxillary division supplies portions of the inferior orbit. The ophthalmic division divides in the cavernous sinus just as it passes into the superior orbital fissure. The lacrimal nerve enters above the annulus of Zinn and proceeds in the extraconal space just inside periorbita along the superolateral orbit to the lacrimal gland and upper eyelid. The frontal nerve runs forward between the levator muscle and the superior periorbita, and exits the orbit at the supraorbital notch. At about the level of the posterior globe it give rise to the supratrochlear nerve, which exits the orbit at the superomedial rim. The nasociliary nerve is a branch of the ophthalmic division that enters the orbit through the superior fissure and annulus of Zinn. It crosses from lateral to medial over the optic nerve after sending small sensory branches that pass through the ciliary ganglion without synapse, and continue to the globe with the short ciliary nerves. As it passes to

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the lateral side of the optic nerve, the nasociliary gives off the long posterior ciliary nerves that extend to the posterior globe. The nasociliary nerve continues forward in the medial orbit where it gives rise to the posterior and anterior ethmoidal nerves. It exits the anterior orbit at the superomedial rim as the infratrochlear nerve. VII.

ARTERIAL SUPPLY TO THE ORBIT

The arterial supply to the orbit is from the internal carotid system through the ophthalmic artery, with anastomotic flow anteriorly from the external carotid system through the superficial facial vessels. The ophthalmic artery enters the orbit through the optic canal inferotemporal to the optic nerve (Fig. 6). In about 83% of individuals the vessel crosses over the nerve to the medial side; in the remaining 17% it crosses below the nerve (13). Shortly after entering the orbit the ophthalmic artery gives off a number of branches with some variability in the sequence. The central retinal artery is usually the first branch. It runs along the inferior aspect of the optic nerve to penetrate the dura about 1 cm behind the globe. The lacrimal artery generally arises next and courses upward and forward, pierces the intermuscular septum, and runs extraconally to the lacrimal gland just above the lateral rectus muscle. It gives rise to the zygomaticotemporal artery that penetrates the lateral wall at about the midorbit, and to the zygomaticofacial artery that runs inferolaterally to exit through a small foramen in the zygomatic bone. Through the latter vessels the lacrimal artery anastomoses with the external carotid system via the transverse fascial and superficial temporal arteries. The lacrimal artery terminates in the lids as the lateral inferior and superior palpebral arteries. The lateral and medial long posterior ciliary arteries arise on either side of the lacrimal artery and run forward parallel to the optic nerve. Each branches into one long and 8–10 short ciliary arteries that penetrate the sclera near the exit of the optic nerve. A number of nutrient branches are given off in this region to the extraocular muscles. As the ophthalmic artery passes toward the medial orbit, the supraorbital branch is given off. This passes through the intermuscular septum medial to the levator muscle, and

Figure 6 Arterial system of the orbit. (From Ref. 2.)

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Figure 7 Venous drainage system from the orbit. (From Ref. 2.)

runs forward with the frontal nerve to the supraorbital notch. In the medial orbit the ophthalmic artery gives rise to the posterior and anterior ethmoidal arteries that enter the ethmoidal foramina. It then continues forward as the nasofrontal artery to exit just above the medial canthus. Here it gives off the inferior and superior medial palpebral arteries to the eyelids, and terminates as the supratrochlear and dorsal nasal arteries with anastomotic connections to the angular vessels. VIII. VENOUS DRAINAGE FROM THE ORBIT Venous drainage is through the superior and inferior ophthalmic veins (Fig. 7). The superior ophthalmic vein originates at the superomedial orbital rim from branches of the angular, supratrochlear, and supraorbital veins (2). As it passes backward along the medial orbit it is joined by branches from the medial and superior rectus muscles, the levator muscle, the superior vortex veins, the anterior ethmoidal vein, and collateral branches from the inferior ophthalmic vein. At about the midorbit it crosses to the lateral orbit just below the superior rectus muscle. Here it is joined by the lacrimal vein, and continues posteriorly to enter the cavernous sinus through the superior orbital fissure. Thickening of the fascial layers in the midorbit can compress the vein against an enlarged superior rectus muscle, resulting in significant orbital congestion and secondary glaucoma. Release of these fascial layers during orbital decompression may be necessary to improve these symptoms. The inferior ophthalmic vein has an indistinct origin in a plexus of small vessels in the inferior orbit. It passes backward along the inferior rectus muscle, picking up branches from the inferior rectus and inferior oblique muscles, the inferior vortex veins, and the lateral rectus muscle. A branch exits through the inferior orbital fissure to join the pterygoid plexus before the vessel terminates at the superior ophthalmic vein just before entering the cavernous sinus.

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REFERENCES 1. Doxanas MT, Anderson RL. Clinical Orbital Anatomy. Baltimore: Williams & Wilkins, 1984. 2. Dutton JJ. Atlas of Clinical and Surgical Orbital Anatomy. Philadelphia: WB Saunders, 1994. 3. Koornneef L. The development of the connective tissue in the human orbit. Acta Morphol Neerl Scand 1976; 14:263–290. 4. Koornneef L. New insights into the human orbit connective tissue. Arch Ophthalmol 1977; 95:1269–1273. 5. Koornneef L. Orbital septa: anatomy and function. Am J Ophthalmol 1979; 86:876–889. 6. Koornneef L. The architecture of the musculo-fibrous apparatus in the human orbit. Acta Morphol Neerl Scand 1977; 15:35–64. 7. Manson PN, Clifford CM, Su CT, Iliff NT, Morgan R. Mechanisms of global support and posttraumatic enophthalmos: I. The anatomy of the ligament sling and its relation to intramuscular cone orbital fat. Plast Reconstr Surg 1986; 77:193–202. 8. Sevel D. The origins and insertions of the extraocular muscles: development, histologic features, and clinical significance. Trans Am Ophthalmol Soc 1986; 84:488–526. 9. Sacks JG. The shape of the trochlea. Arch Ophthalmol 1984; 102:932–933. 10. Ettl A, Priglinger S, Kramer J, Koorrnneef L. Functional anatomy of the levator palpebrae superioris muscle and its connective tissue system. Br J Ophthalmol 1996; 90:702–707. 11. Whitnall SE. Anatomy of the Human Orbit and Accessory Organs of Vision. 2nd ed. London; Oxford Medical Publishers, 1932. 12. Sacks JG. Peripheral innervation of the extraocular muscles. Am J Ophthalmol 1983; 95:520– 527. 13. Hayreh, SS, Dass R. The ophthalmic artery, II. Intra-orbital course. Br J Ophthalmol 1962; 46:165–185.

28 Histopathology of Graves’ Orbital Disease ALAN D. PROIA Duke University Medical Center, Durham, North Carolina, U.S.A.

I.

INTRODUCTION

The histopathology of Graves’ orbital disease has been studied extensively over many decades. The bulk of evidence indicates that the extraocular muscles are the primary site of immunological attack and the resulting myositis causes the exophthalmos noted on clinical examination (1,2). However, many clinical, radiological, and histological studies have noted pathological changes in the orbital connective tissue, leading Nunery to categorize Graves’ ophthalmopathy into two subtypes that may occur separately or together (3). Nunery classified type 1 ophthalmopathy as showing ‘‘retrobulbar fat and connective tissue stimulation with increased fibroblastic activity, glycosaminoglycan deposition, and edema.’’ Type 2 ophthalmopathy is characterized by extraocular myositis involving edema, lymphocytic infiltration, and muscle degeneration. Support for a distinct group of type 1 Graves’ ophthalmopathy is derived from radiological studies (4,5), but there has been no report of histopathologically confirmed abnormalities limited to retrobulbar fat and connective tissue, to my knowledge. Wybar (6), in 1957, noted five pathological processes occurring during Graves’ ophthalmopathy that are necessary for an understanding and explanation of the clinical manifestations: (1) increase in water content (edema), (2) increase in mucin (glycosaminoglycan) content, (3) fibrosis, (4) lymphocytic infiltration, and (5) change in fat content. As will be seen in the remainder of this chapter, these processes occur in each of the orbital tissues affected by Graves’ disease. Before reviewing the histopathology of Graves’ orbitopathy, a synopsis of the systemic pathology of Graves’ disease is presented here. It is apparent that there is significant overlap between the pathology of Graves’ orbitopathy and the alterations that occur in other skeletal muscles, as well as in the skin. 273

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II. SYSTEMIC PATHOLOGY In the era before early recognition and management of Graves’ disease, orbitopathy represented but one systemic manifestation of this disorder (7–9). The systemic pathological findings reported include the following. A.

Thyroid Gland

There was usually moderate enlargement of the thyroid gland with hypertrophy and hyperplasia of follicular epithelial cells (7–9). B.

Thymus Gland

Enlargement of the thymus gland was present in almost all subjects (9–11) due to lymphoid hyperplasia similar to that in patents with myasthenia gravis (11). C.

Lymph Nodes

Lymph nodes were often markedly enlarged, with lymphadenopathy most frequently noted in the neck (9). Some patients had generalized lymphoid hyperplasia even involving Peyer’s patches of the ileum (9). D.

Heart

Patents with Graves’ disease of long duration frequently had cardiac damage, with dilated and hypertrophied ventricles (7,8). These cardiac changes were most likely a compensatory response to persistent tachycardia, and they were not considered to be a direct result of the thyroid disease. E.

Bone

Osteoporosis was frequently noted radiologically and pathologically, and the osteoporosis was attributed to increased osteoclastic activity (8). The abnormal bone findings correlated with increased calcium excretion in the hyperthyroid patients. Acropachy, or thickening of the extremities, was an infrequent manifestation of Graves’ disease (12). Clubbing of the digits was the most common clinical sign of acropachy, and resulted from subperiosteal formation of new bone, along with glycosaminoglycan accumulation in the dermis (12). F. Skeletal Muscles Generalized infiltration of skeletal muscles by lymphocytes was noted in eight of nine patients examined by Dudgeon and Urquhart (11), although the lymphocytic infiltrate was less marked in the deltoid, rectus abdominus, and biceps muscles than in the ocular muscles. Brain and Turnbull also noted lymphocytic infiltration of the sternohyoid muscle in one subject (13). Wilson, in a personal communication to Plummer and Wilder (14), reported ‘‘small and obviously degenerated’’ extraocular muscles and thigh muscles in eight patients with exophthalmic goiter who underwent autopsy prior to 1917. Asboe-Hansen and co-workers observed accumulation of hyaluronidase-sensitive acid mucopolysaccharide within the sarcolemma of muscle fibers and ‘‘considerable amounts’’ of acid mucopolysaccharide in the interstitial connective tissue of the quadriceps femoris and biceps

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brachii muscles in 10 patients with progressive exophthalmos (15). They did not observe inflammation or fatty degeneration in their subjects (15), although Boyd noted fatty degeneration of the quadriceps muscle in a subject mentioned in his textbook (8). Loss of leg strength was more frequent in patients with Graves’ disease reported prior to 1922 (89% of those whose muscle strength was evaluated) than after 1930 (82%), presumably due to more aggressive treatment of the hyperthyroidism (14). Not all authors, however, have found pathological changes in the skeletal muscles of their patients with Graves’ disease. Falconer and Alexander (16) did not detect inflammation of the temporal muscle in three patients with abnormal ocular muscles. Nafziger (17) found histologically normal temporal and thigh muscles in a patient who had chronic inflammation and fibrosis of her extraocular muscles. G.

Skin

Pretibial myxedema, a localized form of thyroid dermopathy, is found in 1–4% of patients with Graves’ disease (18), nearly always in association with Graves’ orbitopathy (19). The lesions may be sharply circumscribed nodules, diffuse nonpitting edema, or may resemble elephantiasis (12,18). Skin lesions may occur on the extensor surfaces of the forearms (20) or at other sites, especially following trauma (12). Deposits of glycosaminoglycan in the dermis, particularly the mid- and lower thirds, with resultant splitting of collagen fibers characterize the lesions (12,18,20). Dermal fibroblasts are undoubtedly the source of the glycosaminoglycan deposits (12,21). A mild chronic inflammatory infiltrate is often found around superficial blood vessels (18). III. PATHOLOGY OF THE EXTRAOCULAR MUSCLES A. Normal Histological Findings The extraocular muscles are similar histologically to skeletal muscles elsewhere in the body, except for increased interstitial tissue between muscle fibers (22) and an altered ratio of resident helper and suppressor T lymphocytes (23). The individual muscle fibers are arranged in fascicles held together by interfascicular connective tissue. This connective tissue condenses to form the perimysium, a compact sheath of collagen, elastic fibers, vessels, and nerves (24) surrounding each fasciculus of muscle. The perimysium extends to encompass individual fibers as the endomysium. It is continuous with the epimysium, the connective tissue sheath that surrounds the entire muscle. The interstitial fibroblasts express human leukocyte antigen (HLA) class II antigens (22). Tallstedt and Norberg (22) found macrophages residing within the interstitium of six specimens of normal extraocular muscle, but they did not detect any T or B lymphocytes using immunohistochemical staining. In contrast, Koornneef and co-workers found T lymphocytes but not B lymphocytes within normal extraocular muscles (23). The T lymphocytes usually occurred singly or as small groups of 2–10 cells, although larger clusters of up to 20 lymphocytes were found (23). The ratio of helper/inducer to suppressor/cytotoxic T lymphocytes was about 0.4, which is significantly lower than that in the blood and normal skeletal muscle (23). The lymphocytes were dispersed both perivascularly and diffusely in the endomysial and epimysial connective tissue. Koornneef and his co-workers confirmed the presence of macrophages within normal extraocular muscles, and they considered these to be the predominant immunocompetent cell at this site (23).

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Graves’ Disease

The extraocular muscles of patients with Graves’ orbitopathy are usually enlarged, as demonstrated by computed tomography (1,5), ultrasonography (25,26), at surgery (17,27,28), or in orbital exenteration specimens examined postmortem (29–31). When viewed by computed tomography (CT), the muscle enlargement varies from minimal in patients with mild Graves’ disease to ‘‘enormous’’ enlargement in those with severe forms of the disease (1). Plummer and Wilder (14) reviewed the records of 2000 patients with exophthalmic goiter and found that the degree of exophthalmos correlated positively with the duration of hyperthyroidism, basal metabolic rate, and loss of strength of the quadriceps femoris muscles. The extraocular muscles are usually not enlarged to the same degree in a particular patient. Some authors consider the inferior rectus muscle to be the most frequently and seriously involved (2,32), while others have noted the superior rectus– levator complex to be most commonly affected (33). At surgery, Nafziger found the extraocular muscles to be increased in size from three to eight times normal in six patents, and they had a consistency varying from rubbery to firm depending on the age of the process and extent of fibrosis (27). In 10 subjects, Kroll and Kuwabara found the extraocular muscles to be enlarged from two to five times normal, and they were firm and rubbery (28). In the orbital exenteration specimens from a 47-year-old man with Graves’ disease, Hufnagel and co-workers (31) found that the cross-sectional diameters of the medial and lateral rectus muscles were 13 ⫻ 8 mm and 11 ⫻ 6 mm, respectively, which was five to six times greater than the normal values cited in the paper (10.3 ⫻ 1.7 mm and 9.2 ⫻ 1.6 mm for the medial and lateral rectus muscles, respectively). Rundle and Pochin measured the orbital volume and weights of the extraocular muscles, lacrimal gland, and residual fibrofatty tissue in orbital exenteration specimens from normal controls and 17 thyrotoxic patients, of whom 9 had exophthalmos noted clinically (29). Exophthalmic patients had an average increase in muscle weight of 25% compared to controls (p ⬍ 0.01). Infiltration of the endomysium and perimysium by mononuclear leukocytes, edema, and glycosaminoglycan accumulation are the pre-eminent features noted on histological examination of extraocular muscles from patients with Graves’ disease (1,11,13,16,17, 22,27,28,30–32,34–41). The mononuclear leukocytes are mostly lymphocytes and plasma cells with a few macrophages (1,32) and a moderate number of mast cells (31). The lymphocytic infiltrate is usually judged to be mild (Fig. 1), and the cells tend to be distributed diffusely with focal perivascular aggregation. The lymphocytes are mostly T cells (39) without a preponderance of either helper/inducer or cytotoxic/suppressor cells (22). One study noted that about 50% of the interstitial lymphocytes expressed IgE, which was also found on extraocular muscle fibers (40). In addition to being infiltrated by lymphocytes and plasma cells, the interstitium is expanded by glycosaminoglycans, edema fluid, and varying degrees of fibrosis depending on the stage of the disease (Fig. 2). The glycosaminoglycans are faintly to lightly basophilic in sections stained with hematoxylin and eosin, but they are readily demonstrated using alcian blue or toluidine blue stains (31,32,36). The glycosaminoglycans are sensitive to digestion with hyaluronidase and have the histochemical properties of a weakly sulfated, polycarboxylated glycosaminoglycan (31). The histochemical properties of the intramuscular glycosaminoglycans are compatible with the increased chondroitin sulfate and hyaluronic acid found by chemical analysis of orbital tissue samples from 14 patients with severe thyroid eye disease (42). Both the glycosaminoglycan accumulation and fibro-

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Figure 1 The extraocular muscles in Graves’ ophthalmopathy typically have a mild infiltrate of lymphocytes and plasma cells within the endomysium and wide separation of the muscle fibers by edema and accumulation of glycosaminoglycans. (H&E; original magnification ⫻400.)

Figure 2 In later stages of Graves’ ophthalmopathy, the endomysium becomes fibrotic and may remain infiltrated by mononuclear leukocytes, as in this case. (H&E; original magnification ⫻400.)

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sis are secondary responses to activation of the endomysial and perimysial fibroblasts (12,32,36,43,44), which is analogous to wound healing in other body sites (45,46). In the latter stages of Graves’ orbitopathy, interstitial fibrosis results in muscle atrophy and degeneration (16,17,27,32,35,37,47). Electron microscopy (28) and electromyography (48) have not detected a primary pathological process in the muscle cells, confirming that the degeneration and atrophy are secondary to the interstitial inflammation and fibrosis. The extraocular muscles may also become infiltrated with adipose tissue late in the disease (37,49), but this is a common and nonspecific finding in chronic muscle disorders (50). IV.

PATHOLOGY OF THE ORBITAL CONNECTIVE AND ADIPOSE TISSUE

A.

Normal Histological Findings

The orbital connective tissue forms an elaborate network connecting and supporting the eye and orbital structures such as muscles, nerves, and blood vessels (23). Adipose tissue, which contains loose interstitial connective tissue, is present between the denser connective tissue septa (23). Koornneef and colleagues found T lymphocytes within normal orbital connective tissue septa and the connective tissue of orbital fat (23), but this observation was not confirmed by Heufelder and Bahn (51), who noted lymphocytes only within the connective tissue of patients with Graves’ orbitopathy. Koornneef and co-workers also found numerous macrophages within normal orbital connective tissue, and these had immunophenotypic characteristics of antigen-presenting cells (23). Kahaly and coinvestigators reported that hyaluronic acid, dermatan sulfate, and chondroitin sulfate represented 25.0%, 38.6%, and 36.4% of the glycosaminoglycans, respectively (42). Singh and Nikiforuk found that normal orbital connective tissue contains hyaluronic acid and dermatan sulfate as the major glycosaminoglycans, with smaller amounts of keratan sulfate, heparin sulfate, chondroitin-4-sulfate, chondroitin-6-sulfate, and heparin also detected (52). If the chondroitin-4-sulfate and chondroitin-6-sulfate fractions in the report by Singh and Nikiforuk are combined, the results are close to those reported by Kahaly and colleagues (42). B.

Graves’ Disease

The ability of Graves’ disease to cause pathological abnormalities in the orbital connective tissue is well documented (16,30,34,36,47,53–55). However, Trokel and Jakobiec did not detect pathological changes in the orbital fat despite examining numerous orbital CT scans and specimens removed during surgery for Graves’ ophthalmopathy (1). The discrepancy between the observations of Trokel and Jakobiec (1) and the other investigators suggests that tissue sampling or the stage, activity, or duration of the disease are important factors to consider in future studies of Graves’ orbitopathy. The histological changes in the orbital connective tissue are similar to those in the extraocular muscles. The histological abnormalities range from perivascular lymphocytic infiltration of the septa (16,30) to extensive fibrosis (13,47). Most commonly, histological examination of the orbital tissues reveals lymphocytes, plasma cells, edema, glycosaminoglycan accumulation, and fibrous thickening of the connective tissue septa (34,36,54,55). Similar to the situation with the extraocular muscles, the lymphocytes in the orbital connective tissue are predominantly T cells (39) and express IgE (40). The cytokines interferon-γ, tumor necrosis factor-α, and interleukin-1α have been detected immunohistochemically in the vicinity of the mono-

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nuclear infiltrate, and these may be important for modulating the activity of nearby fibroblasts (51). As noted previously, chondroitin sulfate and hyaluronic acid account for the glycosaminoglycans that accumulate in the orbital connective in patients with severe thyroid eye disease (42). Much of the interest in orbital connective tissue in Graves’ ophthalmopathy has concerned the possibility that increased orbital fat is the cause of exophthalmos (6,53). Historically, this interest stemmed from Rundle and Pochin’s analysis of the ‘‘fat-free’’ weights and ‘‘fat’’ weights of the extraocular muscles, lacrimal gland, and residual fibrofatty tissue in orbital exenteration specimens from normal controls and 17 thyrotoxic patients (29). In their study, the entire orbital contents from 29 normal control subjects and 17 thyrotoxic patients (9 with exophthalmos noted clinically) were removed and separated into the extraocular muscles, lacrimal gland, and residual fibrofatty tissue (29). The tissues were weighed, and then a portion was dried and extracted with ether to remove lipids. By comparing the dry weights before and after the lipids were extracted, Rundle and Pochin calculated fat-free weights and fat weights. They noted: In proportion to normal values, the fat of each structure is increased more than the fat-free component. Muscle fat is most increased, being more than doubled, and this change is of high statistical significance, and the muscle fat has been significantly raised in each exophthalmic subject. Since, however, muscle fat normally forms only a small proportion of the total orbital tissues, its increase plays a small part in the total increase of bulk. On the other hand, the residual tissue fat is only increased by 20% and the change is established with less certainty. In view of the large amount of such fat normally present, this increase is responsible for a large part of the total bulk increase.

The investigators went on to conclude that ‘‘the increased bulk of the orbital tissues occurring in thyrotoxicosis appears to be due mainly to an increase in fat content of the orbital structures.’’ To interpret the work of Rundle and Pochin properly, it is essential to note that ‘‘fat’’ refers to lipid, not necessarily adipose tissue. It is entirely possible that the orbital tissues accumulated lipid, without an increase in the number of adipocytes. To my knowledge, increased adipose tissue has been confirmed histologically only in the extraocular muscles of patients with Graves’ disease (37,49). As noted previously, this is a common and nonspecific manifestation of chronic muscle disease. Radiological studies have confirmed that the fat compartment of the orbit is expanded in some patients with Graves’ disease (4,5), and Forbes and co-workers found that 8% of subjects with Graves’ disease had only enlargement of the fat compartment (5). These reports, together with the ability of orbital fibroblasts to differentiate into adipocytes in vitro (56), mandate future studies to measure adipocyte size and lipid content in the orbital adipose tissue of control subjects and patients with Graves’ disease. V. OTHER OCULAR PATHOLOGY A. Lacrimal Gland Only a few reports describe histopathological changes in the lacrimal glands of patients with Graves’ disease, although abnormalities in this site appear to be a constant feature of this disorder (1,16,32,55,57). Reese (57) examined specimens from two patients and noted histological changes in the lacrimal glands that were ‘‘identical’’ to those in the extraocular muscles from the same patients. He stated that ‘‘the glandular tissue was in

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all stages of degeneration and was being replaced by edematous fibrous tissue, throughout which were numerous lymphocytes.’’ Reese also commented that the orbital tissue between the lacrimal gland and the extraocular muscles was apparently uninvolved, indicating that the inflammation had not spread from one site to another. Falconer and Alexander examined the orbital contents removed in toto during the autopsy of a 46-year-old woman with bilateral malignant exophthalmos and bilateral corneal ulceration, who died 2 weeks following orbital decompression surgery (16). Both glands had slight, diffuse, periacinar fibrosis with ‘‘some focal lymphocytic collections.’’ Campbell reported that the extraocular muscle histopathological changes also occur within the connective tissue of the lacrimal gland (32). She noted that the fibrosis in the lacrimal gland is usually of a lesser degree than in the muscles and results in only mild atrophy of the acini. Trokel and Jakobiec found the lacrimal gland to be consistently abnormal in Graves’ disease (1). They stated that ‘‘increased numbers of lymphocytes and plasma cells and accompanying edema will be noted within the acini of the lacrimal tissue, as well as in the interlobular septa. Widespread fibrosis and obliteration of the lacrimal tissue, however, are not characteristic, in contrast to idiopathic dacryoadenitis (‘‘pseudotumor’’).’’ B.

Optic Nerve

Compression of the optic nerve by enlarged rectus muscles (31) and anoxia from vascular compression (58) may result in damage to the optic nerve with loss of vision. Severe visual loss from optic neuropathy is estimated to occur in fewer than 5% of patients with Graves’ disease, while mild visual impairment is more frequent (59). All patients with visual loss have signs and symptoms of Graves’ ophthalmopathy, but they may not be florid (59). The incidence of optic neuropathy is not directly related to thyroid activity (60). The most frequent abnormality of the optic nerve seen clinically is papilledema in 25–33% of cases (59). The papilledema in Graves’ disease is indistinguishable histologically from that produced by other causes (32). C.

Cornea

All of the corneal histological changes that occur in Graves’ disease are nonspecific (32). Exposure of the cornea due to proptosis and lagophthalmos may cause the corneal epithelium to become keratinized, ulcerated, or vascularized (32). Panophthalmitis from perforated corneal ulcers is uncommon, being present in only 1.8% of the large series of patients reported by Ogura (61).

VI.

CONCLUSION

Scrutiny of the medical literature, especially from early in the 20th century, indicates that Graves’ orbitopathy is but one manifestation of a systemic process involving multiple tissues, most notably the skeletal muscles and skin. Inflammation and fibroblast activation consistently occur in the extraocular muscles and lacrimal gland, with less frequent involvement of the orbital connective tissue. Whether these orbital tissues are merely a sensitive indicator of a widespread immunological and biochemical derangement or have intrinsically different properties makes it essential to conduct studies of the systemic pathology of Grave’s disease using modern histological and biochemical methods. Future

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studies must also quantitate adipocyte morphology to resolve whether exophthalmos is caused, at least in part, by adipocyte hyperplasia or hypertrophy.

REFERENCES 1. Trokel SL, Jakobiec FA. Correlation of CT scanning and pathologic features of ophthalmic Graves’ disease. Ophthalmology 1981; 88:553–564. 2. Jakobiec FA, Bilyk JR, Font RL. Orbit. In: Spencer WH, ed. Ophthalmic Pathology: An Atlas and Textbook. Vol. 4. 4th ed. Philadelphia: WB Saunders, 1996:2438–2933. 3. Nunery WR. Ophthalmic Graves’ disease: a dual theory of pathogenesis. Ophthalmol Clin North Am 1991; 4:73–87. 4. Peyster RG, Ginsberg F, Silber JH, Adler LP. Exophthalmos caused by excessive fat: CT volumetric analysis and differential diagnosis. Am J Nucl Res 1986; 7:35–40. 5. Forbes G, Gorman CA, Brenan MD, Gehring DG, Ilstrup DM, Earnest F IV. Ophthalmopathy of Graves’ disease: computerized volume measurement of the orbital fat and muscle. Am J Nucl Res 1986; 7:651–656. 6. Wybar KC. The nature of endocrine exophthalmos. Adv Ophthalmol 1957; 7:119–220. 7. Hewlett AW. Pathological Physiology of Internal Diseases. Functional Pathology. New York: Appleton and Co., 1928:636–646. 8. Boyd W. The Pathology of Internal Diseases. Philadelphia: Lea & Febiger, 1931:514–523. 9. MacCallum WG. A Textbook of Pathology. Philadelphia: WB Saunders, 1940:977–984. 10. Halsted WS. The significance of the thymus gland in Graves’s disease. Harvey Lectures 1913– 1914; 224–255. 11. Dudgeon LS, Urquhart AL. Lymphorrhages in the muscles in exophthalmic goitre. Brain 1926; 49:182–186. 12. Smith TJ, Bahn RS, Gorman, CA. Connective tissue, glycosaminoglycans, and diseases of the thyroid. Endocr Rev 1989; 10:366–391. 13. Brain WR, Turnbull HM. Exophthalmic ophthalmoplegia with pathological report on ocular muscles and thyroid gland. Q J Med 1938; 7:293–324. 14. Plummer WA, Wilder RM. Etiology of exophthalmos. Arch Ophthalmol 1935; 13:833–852. 15. Asboe-Hansen G, Iversen K, Wichmann R. Malignant exophthalmos: muscular changes and thyrotrophin content in serum. Acta Endocrinol 1952; 11:376–399. 16. Falconer MA, Alexander WS. Experiences with malignant exophthalmos: relationship of the condition to thyrotoxicosis and to the pituitary thyrotropic hormone. Br J Ophthal 1951; 35: 253–283. 17. Naffziger HC. Progressive exophthalmos following thyroidectomy; its pathology and treatment. Ann Surg 1931; 94:582–586. 18. Weedon D. Skin Pathology. Edinburgh: Churchill Livingstone, 1997:339–352. 19. Maize J, Metcalf J. Metabolic diseases of the skin. In: Elder D, Elenitsas R, Jaworsky C, Johnson B Jr., eds. Lever’s Histopathology of the Skin. 8th ed. Philadelphia: Lippincott– Raven, 1997:369–402. 20. Wortsman J, Dietrich J, Traycoff RB, Stone S. Preradial myxedema in thyroid disease. Arch Dermatol 1981; 117:635–638. 21. Konrad K, Brenner W, Pehamberger H. Ultrastructural and immunological findings in Graves’ disease with pretibial myxedema. J Cutan Pathol 1980; 7:99–108. 22. Tallstedt L, Norberg R. Immunohistochemical staining of normal and Graves’ extraocular muscle. Invest Ophthalmol Vis Sci 1988; 29:175–184. 23. Koornneef L, Schmidt ED, van der Gaag R. The orbit: structure, autoantigens, and pathology. In: Wall JR, How J, eds. Graves’ Ophthalmopathy. Boston: Blackwell Scientific Publications, 1990:1–16.

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24. Bron AJ, Tripathi RC, Tripathi BJ. Wolff ’s Anatomy of the Eye and Orbit. 8th ed. London: Chapel & Hall Medical, 1997:109–110. 25. Werner SC, Coleman DJ, Franzen LA. Ultrasonographic evidence of a consistent orbital involvement in Graves’s disease. N Engl J Med 1974; 290:1447–1450. 26. Hodes BL, Shoch DE. Thyroid ocular myopathy. Trans Am Ophthalmol Soc 1979; 77:80– 103. 27. Naffziger HC. Pathologic changes in the orbit in progressive exophthalmos. Arch Ophthalmol 1933; 9:1–12. 28. Kroll AJ, Kuwabara T. Dysthyroid ocular myopathy: anatomy, histology, and electron microscopy. Arch Ophthalmol 1966; 76:244–257. 29. Rundle FF, Pochin EE. The orbital tissues in thyrotoxicosis: a quantitative analysis relating to exophthalmos. Clin Sci 1944; 5:51–74. 30. Rundle FF, Finlay-Jones LR, Noad KB. Malignant exophthalmos: a quantitative analysis of the orbital tissues. Australas Ann Med 1953; 2:128–135. 31. Hufnagel TJ, Hickey WF, Cobbs WH, Jakobiec FA, Iwamoto T, Eagle RC. Immunohistochemical and ultrastructural studies on the exenterate orbital tissues of a patient with Graves disease. Ophthalmology 1984; 91:1411–1419. 32. Campbell RJ. Pathology of Graves’ ophthalmopathy. In: Gorman CA, Waller RR, Dyer JA, eds. The Eye and Orbit in Thyroid Disease. New York: Raven Press, 1984:25–31. 33. Lacey B, Chang W, Rootman J. Nonthyroid causes of extraocular muscle disease. Surv Ophthalmol 1999; 3:187–213. 34. Smelser, GK. A comparative study of experimental and clinical exophthalmos. Am J Ophthalmol 1937; 20:1189–1203. 35. Burke WJ (for Meadows SP). Exophthalmic ophthalmoplegia with gross papillædema. Proc R Soc Med 1952; 45:229. 36. Riley FC. Orbital pathology in Graves’ disease. Mayo Clinic Proc 1972; 47:975–979. 37. Daiker B. Das gewebliche substrat der verdickten aüßeren Augenmuskeln bei der endokrinen Orbitopathie. Klin Mbl Augenheilkd 1979; 174:843–847. 38. Spoor TC, Martinez AJ, Kennerdell JS, Mark LE. Dysthyroid and myasthenic myopathy of the medial rectus: a clinical pathologic report. Neurology 1980; 30:939–944. 39. Weetman AP, Cohen S, Gatter KC, Fells P, Shine B. Immunohistochemical analysis of the retrobulbar tissues in Graves’ ophthalmopathy. Clin Exp Immunol 1989; 75:222–227. 40. Raikow RB, Dalbow MH, Kennerdell JS, Compher K, Machen L, Hiller W, Blendermann D. Immunohistochemical evidence for IgE involvement in Graves’ orbitopathy. Ophthalmology 1990; 97:629–635. 41. Rosen CE, Raikow RB, Burde RM, Kennerdell JS, Mosseri M, Scalise D. Immunohistochemical evidence for IgA1 involvement in Graves’ ophthalmopathy. Ophthalmology 1992; 99:146– 152. 42. Kahaly G, Fo¨rster G, Hansen C. Glycosaminoglycans in thyroid eye disease. Thyroid 1998; 8:429–432. 43. Bahn RS, Heufelder AE. Pathogenesis of Graves’ ophthalmopathy. N Engl J Med 1993; 329: 1468–1475. 44. Bahn RS. Pathogenesis of Graves’ ophthalmopathy. In: Rapoport B, McLachlan SM, eds. Graves’ Disease: Pathogenesis and Treatment. Boston: Kluwer Academic Publishers, 2000: 249–256. 45. Clark RAF. Wound repair—overview and general considerations. In: Clark RAF, ed. The Molecular and Cellular Biology of Wound Repair. 2nd ed. New York: Plenum Press, 1995: 3–50. 46. Postlethwaite AE, Kang AH. Fibroblasts and matrix proteins. In: Gallin JI, Snyderman R, eds. Inflammation: Basic Principles and Clinical Correlates. 3rd ed. Philadelphia: Lippincott Williams & Wilkins, 1999:227–257.

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47. Merrill HG, Oaks LW. Extreme bilateral exophthalmos: report of two cases with autopsy findings in one. Am J Ophthalmol 1933; 16(3):231–236. 48. Jensen SF. Endocrine ophthalmoplegia: is it due to myopathy or mechanical immobilization? Acta Ophthalmol (Copenh) 1971; 49:679–684. 49. Pochin EE, Rundle FF. Deposition of adipose tissue between ocular muscle fibres in thyrotoxicosis. Clin Sci 1949; 8:89–95. 50. Heffner RR. Muscle biopsy in neuromuscular diseases. Sternberg SS, ed. Diagnostic Surgical Pathology. Vol. 1. 3rd ed. Philadelphia: Lippincott Williams & Williams, 1999:109–129. 51. Heufelder AE, Bahn RS. Detection and localization of cytokine immunoreactivity in retroocular connective tissue in Graves’ ophthalmopathy. Eur J Clin Invest 1993; 23:10–17. 52. Singh SP, Nikiforuk M. Studies in relation to endocrine exophthalmos: the biochemical composition of human retrobulbar connective tissue. Experientia 1976; 32:395–396. 53. Dobyns BM. Present concepts of the pathologic physiology of exophthalmos. J Clin Endocrinol 1950; 10:1202–1230. 54. Wegelius O, Asboe-Hansen G, Lamberg B-A. Retrobulbar connective tissue changes in malignant exophthalmos. Acta Endocrinol 1957; 25:452–456. 55. Tengroth B. Histological studies of orbital tissues in a case of endocrine exophthalmos before and after remission. Acta Ophthalmol (Copenh) 1964; 42:588–591. 56. Sorisky A, Pardasani D, Gagnon A, Smith TJ. Evidence of adipocyte differentiation in human orbital fibroblasts in primary culture. J Clin Endocrinol Metab 1996; 81:3428–3431. 57. Reese AB. Dacryadenitis in hyperthyroidism. Arch Ophthalmol 1935; 13:855–857. 58. Bleeker GM. Changes in orbital tissues and muscles [in] dysthyroid ophthalmopathy. Eye 1988; 2:193–197. 59. Trobe JD. Optic nerve involvement in dysthyroidism. Ophthalmology 1981; 88:488–492. 60. Day RM, Carroll FD. Optic nerve involvement associated with thyroid dysfunction. Arch Ophthalmol 1962; 67:289–297. 61. Ogura JH. Surgical results of orbital decompression for malignant exophthalmos. J Laryngol Otol 1978; 92:181–195.

29 Clinical Manifestations of Graves’ Ophthalmopathy GEORGE B. BARTLEY Mayo Clinic and Mayo Medical School, Rochester, Minnesota, U.S.A.

The clinical features of Graves’ ophthalmopathy—eyelid retraction, lagophthalmos, eyelid lag, exophthalmos, strabismus, and optic neuropathy—are well known. Associated systemic abnormalities include autoimmune thyroid disease, pretibial myxedema, and acropachy. This chapter reviews these manifestations as identified in an incidence cohort of patients with Graves’ ophthalmopathy.

I.

INCIDENCE COHORT

Several years ago, my colleagues and I reviewed the medical records of all patients in Olmsted County, Minnesota, who were diagnosed with Graves’ ophthalmopathy during the 15-year interval 1976–1990 (1–6). The diagnostic criteria, depicted graphically in Figure 1, were as follows (7): eyelid retraction (defined as the upper eyelid resting at or above the superior corneoscleral limbus) had to occur together with objective evidence of thyroid dysfunction, or exophthalmos (defined as an exophthalmometry measurement greater than or equal to 20 mm), or optic nerve dysfunction, or extraocular muscle involvement (either restrictive myopathy or enlarged muscles as determined by computed tomography, magnetic resonance imaging, or ultrasonography). The ophthalmic signs could be either unilateral or bilateral, and confounding causes had to be absent. If the patient did not have eyelid retraction, Graves’ ophthalmopathy was diagnosed only if exophthalmos, optic nerve involvement, or restrictive extraocular myopathy was associated with thyroid dysfunction or abnormal regulation and if no other cause or causes for the ophthalmic features or features was apparent. One-hundred-twenty patients met these criteria, constituting the incidence cohort. Seventeen (14.2%) of the patients were male and 103 (85.8%) were female. All of the 285

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Figure 1 Diagnostic criteria for Graves’ ophthalmopathy. (From Ref. 7.)

patients were white, consistent with the racial demographics of Olmsted County during the study interval. The average age at the time of diagnosis of ophthalmopathy was 44.7 years (range, 8.2–88.7 years). II. FREQUENCY OF SIGNS AND SYMPTOMS The frequencies (3) of the clinical features used for inclusion criteria are summarized in Table 1. One-hundred-eight of 119 patients (90.8%) had eyelid retraction at some point in the clinical course. Exophthalmos was documented in 73 (62.4%) of the 117 patients for whom data were available. Seven patients (5.8%) had optic nerve dysfunction attributable to Graves’ ophthalmopathy. Restrictive extraocular myopathy was documented in 51 patients (42.5%). Unilateral or bilateral extraocular muscle enlargement was confirmed in 12 (54.5%) of the 22 patients in whom imaging studies were performed. Thyroid dysfunction was confirmed by abnormal results of laboratory tests in 113 patients (94.2%) and was evident by some clinical feature in 111 patients (92.5%). One hundred and eight patients (90%) had Graves’ hyperthyroidism, one patient (0.8%) had primary hypothyroidism, four patients (3.3%) had Hashimoto’s thyroiditis, and seven patients (5.8%) were euthyroid. The frequencies of the features used for inclusion criteria, in relation to thyroid status, are outlined in Table 2. The three most common combinations of findings, affecting approximately two-thirds of patients, were hyperthyroidism, eyelid retraction, and exophthalmos (30 patients; 25.0%); hyperthyroidism plus eyelid retraction (26 patients; 21.7%); and hyperthyroidism, eyelid retraction, exophthalmos, and extraocular muscle involvement (25 patients; 20.8%). Only six patients (5.0%) had the complete constellation of so-called classic findings: eyelid retraction, exophthalmos, optic nerve dysfunction, extraocular muscle involvement, and hyperthyroidism. All of the patients with primary hypothyroidism or Hashimoto’s thyroiditis or who were euthyroid had eyelid retraction, but none of these patients had optic nerve dysfunction. The frequencies of clinical signs and symptoms associated with Graves’ ophthalmopathy, present at the time of diagnosis, are given in Table 3. Although 21 patients

Table 1 Frequency of Features Used for Inclusion Criteria Among 120 Incident Cases of Graves’ Ophthalmopathy Feature Eyelid retraction (data for 119 patients) Right eye only Left eye only Both eyes Exophthalmos (data for 117 patients) Right eye only Left eye only Both eyes Optic nerve dysfunction Right eye only Left eye only Both eyes Restrictive extraocular myopathy Right eye only Left eye only Both eyes Evidence of extraocular muscle enlargement (data for 22 patients) Right eye only Left eye only Both eyes Laboratory evidence of thyroid dysfunction Clinical evidence of thyroid dysfunction

N

%

10 10 88

8.4 8.4 73.9

2 8 63

1.7 6.8 53.8

2 1 4

1.7 0.8 3.3

5 8 38

4.2 6.7 31.7

1 2 9 113 111

4.5 9.1 40.9 94.2 92.5

Table 2 Frequency of Features Used for Inclusion Criteria in Relation to Thyroid Status Among 120 Incident Cases of Graves’ Ophthalmopathy Features

Thyroid status Hyperthyroidism

Hypothyroidism Hashimoto’s thyroiditis Euthyroidism

a

Goiter.

Optic Extraocular Eyelid nerve muscle Thyroid retraction Exophthalmos dysfunction involvement dysfunction x x x x x

x x x

x

x x x

x

x x x x x x

x x x x x x

x x x

x x

x x x x x x x x x x x x

xa

N

%

30 25.0 26 21.7 25 20.8 10 8.3 6 5.0 5 4.2 3 2.5 2 1.7 1 0.8 1 0.8 3 2.5 1 3 2 2

0.8 2.5 1.7 1.7

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Table 3 Symptoms and Signs at the Time of Diagnosis of Graves’ Ophthalmopathy Among 120 Incident Cases No. Blurred vision Right eye only Left eye only Both eyes Diplopia Present only when fatigued Present in extremes of gaze Constant but correctable by prisms Constant and not correctable by prisms Lacrimation Right eye only Left eye only Both eyes Pain or ocular discomfort Right eye only Left eye only Both eyes Photophobia Right eye only Left eye only Both eyes Visual acuity (data for 111 patients) Right eye 20/15 20/20 20/25 20/30 20/40 20/60 20/100 Left eye 20/15 20/20 20/25 20/30 20/40 Hand motions Visual field defect (demonstrated by perimetry) Right eye Generalized depression Altitudinal defect Left eye Generalized depression Altitudinal defect Color vision defect Right eye Inherited dyschromatopsia Graves’ optic neuropathy

%

1 1 7 20 4 9 3 4

0.8 0.8 5.8 16.7 3.3 7.5 2.5 3.3

5 2 18

4.2 1.7 15.0

7 3 26

5.8 2.5 21.7

1 1 17

0.8 0.8 14.2

3 90 8 3 4a 2b 1c

2.7 81.1 7.2 2.7 3.6 1.8 0.9

3 90 10d 3 4e 1f

2.7 81.1 9.0 2.7 3.6 0.9

1 1

0.8 0.8

1 1

0.8 0.8

2 1

1.7 0.8

Clinical Manifestations

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Table 3 Continued

Left eye Inherited dyschromatopsia Graves’ optic neuropathy Eyelid retraction Upper eyelids (data for 111 patients) Right upper eyelid only Left upper eyelid only Both upper eyelids Right upper eyelid Amount (mm) Mean, 2.2 ⫾ 1.0 Median, 2 Range, 1–4 Grade Mild (⬍2 mm) Moderate (2–4 mm) Severe (⬎4 mm) Left upper eyelid Amount (mm) Mean, 2.0 ⫾ 1.0 Median, 2 Range, 1–5 Grade Mild (⬍2 mm) Moderate (2–4 mm) Severe (⬎4 mm) Lower eyelids (data for 102 patients) Right lower eyelid only Left lower eyelid only Both lower eyelids Right lower eyelid Amount (mm) Mean, 1.8 ⫾ 0.8 Median, 2 Range, 1–3 Grade Mild (⬍2 mm) Moderate (2–4 mm) Severe (⬎4 mm) Left lower eyelid Amount (mm) Mean, 2.0 ⫾ 0.9 Median, 2 Range, 1–3 Grade Mild (⬍2 mm) Moderate (2–4 mm) Severe (⬎4 mm)

No.

%

2 1

1.7 0.8

13 11 61

11.7 9.9 55.0

47 27 0

42.3 24.3 0

46 25 1

41.4 22.5 0.9

0 2 22

0 2.0 21.6

13 8 0

12.7 7.8 0

13 11 0

12.7 10.8 0

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Table 3 Continued

Eyelid fissure (mm) Right Mean, 10.9 ⫾ 2.3 Median, 11 Range 7–15 Left Mean, 11.1 ⫾ 2.4 Median, 10.5 Range, 6–18 Lagophthalmos (data for 102 patients) Right eyelids only Left eyelids only Both right and left eyelids Right eyelids Grade Mild (⬍2 mm) Moderate (2–4 mm) Severe (⬎4 mm) Left eyelids Grade Mild (⬍2 mm) Moderate (2–4 mm) Severe (⬎4 mm) Lid lag (data for 105 patients) Right upper eyelid only Left upper eyelid only Both upper eyelids Eyelid fullness (data for 117 patients) Right eyelids only Left eyelids only Both right and left eyelids Right eyelids Grade Mild Moderate Severe Left eyelids Grade Mild Moderate Severe Exophthalmometry (mm; data for 111 patients) Right eye Mean, 18.8 ⫾ 2.6 Median, 18 Range, 12–26 Left eye Mean, 18.9 ⫾ 2.9 Median, 19 Range, 11–26

No.

%

2 3 8

2.0 2.9 7.8

8 2 0

7.8 2.0 0

9 2 0

8.8 2.0 0

9 6 37

8.6 5.7 35.2

3 4 31

2.6 3.4 26.5

27 6 1

23.1 5.1 0.9

26 8 1

22.2 6.8 0.9

Table 3 Continued

Corneal staining (data for 108 patients) Right eye only Left eye only Both eyes Superior limbic keratoconjunctivitis (data for 109 patients) Right eye only Left eye only Both eyes Conjunctival injection (data for 116 patients) Right eye only Left eye only Both eyes Chemosis (data for 116 patients) Right eye only Left eye only Both eyes Extraocular muscle dysfunction (data for 116 patients) Right eye only Left eye only Both eyes Resistance of globe to retropulsion (data for 46 patients) Right eye only Left eye only Both eyes Intraocular pressure, mmHg (data for 92 patients) Right eye Mean, 16.4 ⫾ 3.2 Median, 16 Range, 8–27 Left eye Mean, 16.2 ⫾ 3.4 Median, 16 Range, 10–29 Optic disk appearance (data for 114 patients) Right eye only Choked Pale Left eye only Choked Pale Both eyes Choroidal folds (data for 108 patients) Right eye only Left eye only Both eyes

No.

%

1 1 9

0.9 0.9 8.3

0 0 1

0 0 0.9

3 2 35

2.6 1.7 30.2

2 1 24

1.7 0.9 20.7

5 4 21

4.3 3.4 18.1

1 2 11

2.2 4.3 23.9

1 1

0.9 0.9

0 0 0

0 0 0

0 0 0

0 0 0

a One patient had Graves’ optic neuropathy, two patients had cataracts, and one patient had Fuchs’ corneal dystrophy. b Both patients had cataracts. c Patient had Graves’ optic neuropathy. d One patient had Graves’ optic neuropathy. e One patient had Graves’ optic neuropathy, one patient had cataract, one patient had cataract and Fuchs’ corneal dystrophy, and one patient had Fuchs’ corneal dystrophy. f Patient had cataract.

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Figure 2 Symptoms associated with Graves’ ophthalmopathy at the initial and final ophthalmic examinations. (From Ref. 1.)

Figure 3 Signs associated with Graves’ ophthalmopathy at the initial and final ophthalmic examinations. (From Ref. 1.)


293

(17.5%) were not examined by an ophthalmologist after the initial visit, follow-up information regarding symptoms was obtained from mail and telephone surveys (1,6). In the remaining patients, the mean and median intervals between the initial and final ophthalmic examinations were 4.8 years and 3.6 years, respectively. Follow-up was less than 1 year for 37 (30.8%) of the 120 incident cases, but exceeded 5 years for 46 patients (38.3%) and 10 years for 22 patients (18.3%). As depicted graphically in Figures 2 and 3, nearly all signs and symptoms improved over time. Thyroid dermopathy, also known as pretibial myxedema, was present in five patients (4.2%) and thyroid acropachy was diagnosed in one patient (0.8%). Evidence of concomitant systemic disease, particularly autoimmune disorders, was sought. None of the patients in the incidence cohort had type I (insulin-dependent) diabetes mellitus, pernicious anemia, or systemic lupus erythematosus. Three patients (2.5%) had breast carcinoma, two patients (1.7%) had type II diabetes mellitus, and one patient each (0.8%) had myasthenia gravis, rheumatoid arthritis, ulcerative colitis, Crohn’s disease, Rendu–Osler–Weber syndrome, Paget’s disease, pituitary adenoma, laryngeal carcinoma, fallopian tube carcinoma, and colon carcinoma.

III. COMMENTS ON SELECTED CLINICAL FEATURES A. Eyelid Retraction Eyelid retraction was the most common sign of Graves’ ophthalmopathy in the incidence cohort, present at diagnosis in 75% of patients and occurring at some point in the clinical course in more than 90%. The pre-eminence of eyelid retraction as a characteristic feature of dysthyroid ophthalmopathy has been known since at least 1869, when Stellwag (8) wrote that the sign was almost pathognomonic for Basedow’s disease. Pochin (9), in the late 1930s, may have been the first author to describe unilateral retraction in association with Graves’ disease. Although the eyelid malposition may improve as thyrotoxicosis is treated (10), in a sizable minority of patients, and in those who do not have hyperthyroidism, eyelid retraction may persist in as many as 40% of affected patients for many years (11), presumably from scarring between the inflamed eyelid retractors and the surrounding orbital tissues (12,13). Nearly one-half (45%) of the patients in our incidence cohort still had eyelid retraction at the most recent examination. Of interest is a study of 10,809 patients with Graves’ disease who had been rendered euthyroid, in which only 21 patients (0.2%) reportedly had persistent upper eyelid retraction (14). The differential diagnosis of eyelid retraction is extensive and has been published elsewhere (15,16). B.

Exophthalmos

Moore (17), in 1920, stated that it is ‘‘undeniable that increase of orbital fat is the usual cause of the exophthalmos of Graves’s disease.’’ His opinion was based on finding an increase in fat both in a patient on whom he performed an autopsy and in another patient in whom he ‘‘picked away piecemeal as much orbital fat as possible’’ to treat severe proptosis. In the surgical case, he noted that the extraocular muscles were ‘‘greatly swollen’’ but did not consider the abnormality a contributing factor for exophthalmos. Rundle and Pochin (18) published in 1945 the results of a pathological study in which the fat content in the orbital tissues was measured. They concluded that exophthalmos and eyelid

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retraction were caused by increased orbital fat and fatty involvement of the levator palpebrae superioris, respectively. The advent of computed tomography and improved histopathological techniques confirmed that proptosis in most patients results primarily from enlarged extraocular muscles and glycosaminoglycan deposition (19), although in some patients the orbital fat compartment alone may be increased (20,21). Graves’ disease is the most common cause of both bilateral and unilateral exophthalmos (22–25), but the finding often does not correlate well with other facets of Graves’ ophthalmopathy and has been considered by several authorities to be a relatively insensitive diagnostic feature (26–30). Proptosis, along with other soft tissue signs, has been thought to improve over time regardless of treatment (31–34). In contrast, a mild but statistically significant increase in proptosis between the initial and final examinations was measured among patients in the incident cohort. There is precedent for this trend in two studies that were not population-based. Hales and Rundle (11), in their 15-year follow-up report of 104 patients with Graves’ ophthalmopathy, noted that exophthalmometry measurements were unchanged in 75 patients (72%), increased by more than 2 mm in 24 patients (23%), and decreased by the same increment in only five patients (5%). Streeten and co-workers (35) studied 122 patients with Graves’ disease who underwent exophthalmometry annually for 3–19 years after correction of thyrotoxicosis (by radioiodine in 81% of patients); measurements remained stable in 97 patients (80%), increased 2 mm or more in 19 patients (16%), and decreased 2 mm or more in seven patients (5.7%). C.

Superior Limbic Keratoconjunctivitis

The description of superior limbic keratoconjunctivitis (SLK) as a discrete clinical entity is attributed to Theodore (36–38). Its putative association with thyroid dysfunction originated in a letter to the editor in 1968 by Tenzel (39), who noted that three of four patients with SLK had markedly increased serum levels of protein-bound iodine, although without clinical evidence of hyperthyroidism. Theodore (40) commented on this observation by stating that he had examined patients with either increased or decreased protein-bound iodine levels. Numerous authors subsequently described hyperthyroidism in patients with SLK; in some studies the prevalence of thyroid dysfunction was as high as 50% (41–49). Conversely, other investigators have documented normal results of thyroid function studies in patients with this ocular abnormality (50,51). One report (52) described identical twins, Hispanic women aged 32 years, in whom SLK developed at age 16 years in each patient. No evidence of dysthyroid or other autoimmune disease was found in either patient, leading the author to favor a genetic basis for SLK. Four (3.3%) of the 120 incident cases in the current study had documented SLK at some point in their clinical course: one patient had the finding at both initial and final examination, one patient had SLK at the most recent examination only, and two patients had SLK at a single interim visit. Because this frequency is lower than might be expected if a true association between SLK and thyroid dysfunction exists, we studied a group of 57 patients with SLK who were examined at the Mayo Clinic between 1980 and 1993 (53). Thirty-seven patients (64.9%) had objective evidence of thyroid dysfunction. Of patients with SLK and thyroid disease, 33 (89.2%) had ophthalmopathy. The eye disease was sufficiently severe in 16 of these patients (48.5%) to require orbital decompression, leading us to conclude that SLK not only is associated with thyroid dysfunction, but also appears to be a prognostic marker for severe Graves’ ophthalmopathy.


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D. Thyroid Dermopathy and Thyroid Acropachy Pretibial myxedema and clubbing of the digits are uncommon extrathyroidal manifestations of autoimmune thyroid disease. Thyroid dermopathy rarely occurs without coexistent ophthalmopathy (54–57) and has been considered a possible marker for more severe disease. A study by Fatourechi and associates (58), however, found no difference in the clinical characteristics and response to transantral decompression in patients with pretibial myxedema and those who did not have dermopathy. Acropachy is clubbing of the fingers and toes, subperiosteal new bone formation (which is radiographically distinct from pulmonary osteoarthropathy) in the phalanges and distal long bones, and swelling over the extremities. Its association with thyroid dysfunction was originally noted by Thomas in 1933 (59) and has subsequently been described by several authors (56,57,60–65). Acropachy is considered to be even more unusual than thyroid dermopathy and allegedly is not found without concomitant eye and skin changes. Pretibial myxedema and thyroid acropachy were present in 4% and 1%, respectively, of the incident cases in the current study. The severity of ophthalmopathy was not worse among these patients, none of whom had optic neuropathy or underwent orbital decompression.

E.

Concomitant Systemic Diseases

No significant associations between Graves’ ophthalmopathy and concomitant systemic disorders were found. Diabetes mellitus occurred in only 2 of the 120 incident cases, which may appear to be fewer than expected. Prevalence rates of diabetes mellitus in Rochester, Minnesota, were determined by Melton and associates (66). From this information it can be calculated that 2.71 cases of diabetes mellitus would be expected among the 120 patients we studied, which is similar to the frequency documented. The association of myasthenia gravis with hyperthyroidism, Graves’ ophthalmopathy, or both has been recognized for many years (67–77). Although approximately 5% of patients with myasthenia gravis have Graves’ disease, only 1% or fewer patients with thyroid dysfunction have concomitant myasthenia (72,77). This result is consistent with the finding of 1 patient (0.8%) with myasthenia among the 120 incident cases of Graves’ ophthalmopathy in this study. Brain (78) noted the presence of several miscellaneous conditions, including persistent lactation and gynecomastia, lipodystrophy, and generalized edema, in patients with Graves’ ophthalmopathy, and Furszyfer and colleagues (79) found a correlation between pernicious anemia and Graves’ disease. No such associations were noted among the patients studied in the current report.

IV.

CONCLUSIONS

Eyelid retraction is the most common clinical sign of Graves’ ophthalmopathy and is key to establishing the diagnosis. The complete constellation of so-called ‘‘classic’’ features— hyperthyroidism, eyelid retraction, exophthalmos, restrictive extraocular myopathy, and optic neuropathy—occurs relatively infrequently.

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REFERENCES 1. Bartley GB. The epidemiologic characteristics and clinical course of ophthalmopathy associated with autoimmune thyroid disease in Olmsted County, Minnesota. Trans Am Ophthalmol Soc 1994; 92:477–588. 2. Bartley GB, Fatourechi V, Kadrmas EF, Jacobsen SJ, Ilstrup DM, Garrity JA, Gorman CA. The incidence of Graves’ ophthalmopathy in Olmsted County, Minnesota. Am J Ophthalmol 1995; 120:511–517. 3. Bartley GB, Fatourechi V, Kadrmas EF, Jacobsen SJ, Ilstrup DM, Garrity JA, Gorman CA. Clinical features of Graves’ ophthalmopathy in an incidence cohort. Am J Ophthalmol 1996; 121:284–290. 4. Bartley GB, Fatourechi V, Kadrmas EF, Jacobsen SJ, Ilstrup DM, Garrity JA, Gorman CA. The chronology of Graves’ ophthalmopathy in an incidence cohort. Am J Ophthalmol 1996; 121:426–434. 5. Bartley GB, Fatourechi V, Kadrmas EF, Jacobsen SJ, Ilstrup DM, Garrity JA, Gorman CA. The treatment of Graves’ ophthalmopathy in an incidence cohort. Am J Ophthalmol 1996; 121:200–206. 6. Bartley GB. Long-term follow-up of Graves ophthalmopathy in an incidence cohort. Ophthalmology 1996; 103:958–962. 7. Bartley GB, Gorman CA. Diagnostic criteria for Graves’ ophthalmopathy. Am J Ophthalmol 1995; 119:792–795. 8. Stellwag G. Ueber gewisse Innervationssto¨rungen bei der Basedow’schen Krankheit. Wien Med Wochenschr 1869; 19:737–740. 9. Pochin EE. Unilateral retraction of the upper lid in Graves’ disease. Clin Sci 1937–8; 3:197– 209. 10. Eden KC, Trotter WR. Lid-retraction in toxic diffuse goitre. Lancet 1942; 2:385–387. 11. Hales IB, Rundle FF. Ocular changes in Graves’ disease: a long-term follow-up study. Q J Med 1960; 29:113–126. 12. Hodes BL, Shoch DE. Thyroid ocular myopathy. Trans Am Ophthalmol Soc 1979; 77:80103. 13. Grove AS Jr. Upper eyelid retraction and Graves’ disease. Ophthalmology 1981; 88:499– 506. 14. Ohnishi T, Noguchi S, Murakami N, Nakahara H, Hoshi H, Jinnouchi S, Futami S, Nagamachi S, Watanabe K. Levator palpebrae superioris muscle: MR evaluation of enlargement as a cause of upper eyelid retraction in Graves’ disease. Radiology 1993; 188:115–118. 15. Bartley GB. The differential diagnosis and classification of eyelid retraction. Trans Am Ophthalmol Soc 1995; 93:371–389. 16. Bartley GB. The differential diagnosis and classification of eyelid retraction. Ophthalmology 1996; 103:168–176. 17. Moore RF. A note on the exophthalmos and limitation of the eye movements of Graves’ disease. Lancet 1920; 2:701. 18. Rundle FF, Pochin EE. The orbital tissues in thyrotoxicosis: a quantitative analysis relating to exophthalmos. Clin Sci 1945; 5:51–74. 19. Trokel SL, Jakobiec FA. Correlation of CT scanning and pathologic features of ophthalmic Graves’ disease. Ophthalmology 1981; 88:553–564. 20. Forbes G, Gorman CA, Gehring D, et al. Computer analysis of orbital fat and muscle volumes in Graves ophthalmopathy. Am J Neuroradiol 1983; 4:737–740. 21. Forbes G, Gorman CA, Brennan MD, Gehring DG, Ilstrup DM, Earnest F, IV. Ophthalmopathy of Graves’ disease: computerized volume measurements of the orbital fat and muscle. Am J Neuroradiol 1986; 7:651–656. 22. Drescher EP, Benedict WL. Asymmetric exophthalmos. Arch Ophthalmol 1950; 44:109–128. 23. Schultz RO, Richards RD, Hamilton HE. Asymmetric proptosis. Am J Ophthalmol 1961; 52: 10–15.


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51. Corona R. Superior limbic keratoconjunctivitis apparently related to particulate material from a ventilation system. (Letter to the Editor) N Engl J Med 1989; 320:1354. 52. Darrell RW. Superior limbic keratoconjunctivitis in identical twins. Cornea 1992; 11:262– 263. 53. Kadrmas EF, Bartley GB. Superior limbic keratoconjunctivitis. A prognostic sign for severe Graves ophthalmopathy. Ophthalmology 1995; 102:1472–1475. 54. Morris JC III, Hay ID, Nelson RE, Jiang NS. Clinical utility of thyrotropin-receptor antibody assays: comparison of radioreceptor and bioassay methods. Mayo Clin Proc 1988; 63:707– 717. 55. Kriss JP, Pleshakov V, Chien JR. Isolation and identification of the long-acting thyroid stimulator and its relation to hyperthyroidism and circumscribed pretibial myxedema. J Clin Endocrinol 1964; 24:1005–1028. 56. Gorman CA. Unusual manifestations of Graves’ disease. Mayo Clin Proc 1972; 47:926–933. 57. Smith TJ, Bahn RS, Gorman CA. Connective tissue, glycosaminoglycans, and diseases of the thyroid. Endocr Rev 1989; 10:366–391. 58. Fatourechi V, Garrity JA, Bartley GB, Bergstralh EJ, Gorman CA. Orbital decompression in Graves’ ophthalmopathy associated with pretibial myxedema. J Endocrinol Invest 1993; 16: 433–437. 59. Thomas HM Jr. Acropachy: Secondary subperiosteal new bone formation. Arch Intern Med 1933; 51:571–588. 60. Peard MC (for Greene R). Lymphadenoid goitre with hypothyroidism, exophthalmos, pretibial myxoedema and acropachy. Proc R Soc Med 1961; 54:342–343. 61. Cushing EH. ‘‘Club fingers’’ and hypertrophic pulmonary osteoarthropathy. Int Clin 1937; 2 Series 47:200–205. 62. Rynearson EH, Sacasa CF. Hypertrophic pulmonary osteo-arthropathy (acropachy) afflicting a patient who had postoperative myxedema and progressive exophthalmos. Proc Staff Meet Mayo Clin 1941; 16:353–356. 63. Greene R. Thyroid acropachy. Proc R Soc Med 1951; 44:159–161. 64. Danforth WH, Humphrey HA. Hypertrophic osteoarthropathy and pretibial myxedema associated with Graves’ disease. J Clin Endocrinol Metab 1958; 18:1302–1307. 65. Gimlette TMD. Thyroid acropachy. Lancet 1960; 1:22–24. 66. Melton LJ III, Ochi JW, Palumbo PJ, Chu CP. Sources of disparity in the spectrum of diabetes mellitus at incidence and prevalence. Diabetes Care 1983; 6:427–431. 67. Mulvany JH. The exophthalmos of hyperthyroidism: a differentiation in the mechanism, pathology, symptomatology, and treatment of two varieties, part I. Am J Ophthalmol 1944; 27: 589–612. 68. Mulvany JH. The exophthalmos of hyperthyroidism: a differentiation in the mechanism, pathology, symptomatology, and treatment of two varieties, part III. Am J Ophthalmol 1944; 27:820–832. 69. Meyerstein R. Ueber das combinirte Vorkommen von Myasthenie und Basedow’scher Krankheit. Neurol Centralbl 1904; 1089–1093. 70. Rennie GE. Exophthalmic goitre combined with myasthenia gravis. Rev Neurol Psychiatry 1908; 6:229–233. 71. Collier J. Nuclear ophthalmoplegia, with especial reference to retraction of the lids and ptosis and to lesions of the posterior commissure. Brain 1927; 50:488–498. 72. Millikan CH, Haines SF. The thyroid gland in relation to neuromuscular disease. Arch Intern Med 1953; 92:5–39. 73. Engel AG. Thyroid function and myasthenia gravis. Arch Neurol 1961; 4:663–674. 74. Johns RJ, Knox DL, Walsh FB, Renken HJ. Involuntary eye movements in a patient with myasthenia and hyperthyroidism. Arch Ophthalmol 1962; 67:35–41. 75. Sahay BM, Blendis LM, Greene R. Relation between myasthenia gravis and thyroid disease. Br Med J 1965; 1:762–765.


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30 Orbital Imaging in Thyroid Eye Disease ELI CHANG Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, U.S.A. MATTHEW W. WILSON University of Tennessee Health Science Center and St. Jude Children’s Research Hospital, Memphis, Tennessee, U.S.A. MARY E. SMITH University of Tennessee Health Science Center, Memphis, Tennessee, U.S.A.

I.

INTRODUCTION

Computed tomography (CT) is an important tool in the evaluation and management of thyroid eye disease (TED). The technique for CT scanning was originated by Sir Godfrey Hounsfield at Electrical and Musical Industries (EMI) in England and led to his being awarded the Nobel Prize for medicine in 1979 (1,2). Originally known as EMI scans, early CT scanners of the 1970s were limited in their ability to evaluate the orbits. Scanners available today have a higher degree of spatial resolution and generate less artifact, allowing for both greater accuracy and consistency in the diagnosis of orbital lesions. Technical advances, such as the advent of the helical CT scanner, have allowed thinner tissue sections and reformatted images of vastly improved quality, most notably threedimensional views of the orbit that can be used to assess volume and to plan surgical decompression of thyroid patients (3,4). In computed tomography of the orbits, both soft tissue and bone windows may be required to assess the extent of a lesion. These windows are based on Hounsfield units (H), an arbitrary scale of attenuation coefficients with water set at 0, air at ⫺1000 H, and bone at ⫹1000 H. A central soft tissue window is usually near 0 to 40 H, with a width of 200 to 400 H. This allows for adequate contrast between fat and air. Bone windows may have a central level between 40 and 300 H, with an appropriately wide width on either side. The wide window width is necessary because of the variable density of bone. For TED, soft tissue windows are used (5), and tissue sections of 3 mm are adequate. Thinner sections may improve the image resolution of small-diameter structures, such as the optic nerve. 301

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Figure 1 A scout image from computed tomography of the orbit illustrates the orbitomeatal line. Both coronal and axial images are useful in diagnosing and assessing the severity of TED. Coronal images are obtained with the patient in a prone position with the head maximally hyperextended. Sections are made at 75 degrees incident to the canthomeatal line. Axial images are performed in sections parallel to the orbitomeatal line (a line extending from the upper margin of the external auditory meatus to the inferior orbital rim; Fig. 1). Data obtained from axial scanning can be reformatted into coronal, sagittal, or oblique sections by computer generation. Although reformatted images require less examination time and radiation exposure, direct images afford superior spatial resolution. Images formed by multiplanar reconstruction (MPR) depend on the number of sections imaged, thickness of each section, and the amount of overlap between each section. MPR is used for patients who are unable to position for extended periods of time, possess limited mobility, or have extensive dental or metallic appliances that may result in imaging artifacts. Orbital fat provides a natural contrast for CT imaging. Fat absorbs fewer x-rays than water and is imaged as a black, low-density area that contrasts with the higher-density image of the extraocular muscles and optic nerve. Intravenous contrast media may be a helpful adjunct in CT scanning. Post-contrast enhancement may help further to delineate normal from abnormal tissue, especially if there is intracranial extension of an orbital lesion. Intravenous contrast has not been shown to be helpful in the evaluation of TED because the intraorbital fat already provides a natural contrast to the adjacent inflamed soft tissues (5). II. CT FINDINGS IN THYROID EYE DISEASE Enlargement of the extraocular muscles is the hallmark finding of TED (6,7). Muscle enlargement can be unilateral or bilateral, and marked asymmetry is often present. The

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most commonly involved extraocular muscle is the inferior rectus. An isolated, enlarged inferior rectus may be mistaken for an orbital apex tumor on axial images, where it may appear as an isolated mass (Fig. 2). The medial rectus is the second most commonly involved muscle followed by the superior and lateral recti. The superior oblique muscle is rarely affected. On CT, the rectus muscles are well defined with sharp borders. They are spindle shaped with the majority of thickening occurring within the muscle belly (Fig. 3). The muscle tendons are spared by the orbital inflammation. This is in contrast to idiopathic orbital inflammation, which frequently causes thickening of both the muscle belly and tendon. Other diseases that may cause diffuse or focal enlargement of the extraocular muscle include metastases, lymphoma, vascular malformations, eosinophilic granuloma, and trichinosis. Axial images may show bowing or remodeling of the lamina papyracea in cases in which the enlarged medial rectus presses on the medial orbital wall. Coronal images provide the best view of both the inferior and superior rectus muscles when seen in cross section (Fig. 4). There may be anterior displacement of the orbital fat in patients affected with TED. Inflammatory infiltrates and secondary tissue edema lead to increased intraorbital pressure and subsequent displacement of the orbital fat. On CT, anterior bowing of the orbital septum may be seen. Less common signs of TED on CT include enlargement of the orbital veins and the lacrimal gland. Increased orbital congestion and severe muscle enlargement can cause dilation of the superior ophthalmic vein (Fig. 5). Vascular malformations, such as carotid– cavernous sinus fistulas and arteriovenous malformations, may mimic this sign. Lacrimal gland enlargement is a nonspecific finding almost always associated with muscle enlargement and proptosis. Perhaps of most interest in imaging patients with TED is the status of the optic nerve (8). Axial and coronal images allow detailed inspection of the orbital apex, where

Figure 2 Axial computed tomographic image of a patient with Graves’ disease and isolated enlargement of the inferior rectus masquerading as an orbital apex tumor.

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Figure 3 Computed tomographic axial image of a patient with Graves’ disease and enlargement of the medial rectus muscle. Note the enlargement of the muscle belly with relative sparing of the tendon insertion.

Figure 4 Computed tomographic coronal image shows comparison of the rectus muscles and optic nerves between the two sides.

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Figure 5 Computed tomographic scan shows enlargement of the superior ophthalmic vein because of compression and orbital congestion.

enlarged muscle bellies can be seen to compress the optic nerve (Fig. 6). The CT scan may show enlargement of the optic nerve when compression at the orbital apex causes cerebrospinal fluid to build up within the optic nerve sheath. CT imaging also plays an important role in the preoperative evaluation for orbital decompression surgery (9). Imaging shows the anatomical relationship of the orbit to both the sinus cavities and the cribriform plate. From these images, the surgeon can decide

Figure 6 Axial computed tomographic image in a patient with Graves’ disease and bilateral optic nerve compression at the orbital apex.

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both on the surgical approach and the extent of decompression required. Special attention should be directed toward the cribriform plate. A low-lying cribriform plate presents the possibility of a cerebrospinal fluid leak and subarachnoid hemorrhage.

III. MAGNETIC RESONANCE IMAGING The demonstration of human anatomy using the techniques of magnetic resonance (MR) imaging was first accomplished by a team at the University of Nottingham in 1976. This accomplishment rests on a broadly based body of knowledge and techniques that encompass much of modern physics. MR images are composed of signals generated by the interaction of magnetic fields, radiowaves, and proton nuclei of body tissues (10,11). The MR image is based on the principle that the nuclei of certain atoms become polarized or aligned (display magnetic moments) when placed in a static magnetic field. This magnetic property is present only if the nucleus contains an odd number of protons, such as hydrogen, sodium, and phosphorus in human tissue. Normally, these magnetic moments are randomly oriented. When a homogeneous magnetic field is generated by a magnet with a strength of 0.2 to 1.5 Tesla, tissue protons align with or against the direction of the external magnetic field. Protons may align parallel and antiparallel with the magnetic field. Because there is a slight preponderance of protons aligned in the parallel direction, there is a net magnetic vector in this direction. Short radiofrequency (RF) pulses can be applied, causing the net magnetic vector to rotate away from its alignment as the tissue protons move to a higher energy level or more antiparallel state. The angle of rotation is dependent on the amplitude and duration of RF pulse applied on the field. After the RF pulse, the tissue protons realign as the energy is released over time. This phenomenon of realignment combined with the release of energy is known as relaxation. T1, the longitudinal relaxation time, is the time necessary for protons to realign with the longitudinal magnetic field direction. T2, the transverse relaxation time, is the time necessary for the magnetic vectors to redistribute themselves 360 degrees around the mean magnetic direction. T1 and T2 are time constants resulting from inherent tissue characteristics that correspond to the behavior of protons whose nuclei precess in response to applied magnetic and radiofrequency stimuli. Therefore, T1 and T2 can be used to differentiate tissue types. The energy emitted is received by an antenna coil and transformed by a computer into a recognizable image. T1 and T2 in combination with different modifiers, such as pulse sequence, repetition times, and echo delay, allow many different types of images to be generated. Without repositioning the patient, anatomical images can be generated in all planes simultaneously by spatially localizing signals and processing signals from different tissues that exhibit different spin behaviors after manipulation by RF pulses. Orbital sections, in particular, may be preformed in slices ranging from 1.5 to 10 mm, with 3 mm being adequate for TED. Gadolinium is used as an intravenous contrast agent for MR imaging. This rare earth element is chelated with diethylenetriaminepenta-acetic acid to form a nontoxic paramagnetic compound that alters the signal characteristics of some tissue, changing its visibility relative to background structures in the presence of altered permeability as a result of infarction, tumor, inflammation, or trauma. Orbital fat enhances brightly on T1-weighted MR images and can obscure anatomical details in adjacent orbital tissue. It is, therefore, necessary to adjust the emitted signal,

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Figure 7 Magnetic resonance T1-weighted axial image shows enlargement of the rectus muscles and compression of the optic nerve.

intensity to suppress the brightness of the orbital fat and permit better visualization of the other orbital tissues. IV.

MR FINDINGS IN THYROID EYE DISEASE

The MR findings in TED are similar to those on CT (12). Extraocular muscle enlargement and optic nerve compression can be appreciated with both axial and coronal images

Figure 8 T1-weighted magnetic resonance images with gadolinium shows enhancement of the inflamed extraocular muscles involved in Graves’ disease.

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(Fig. 7). Differences in the T1- and T2-weighted images reflect the pathophysiology of TED. The inflamed extraocular muscles appear bright on T2 images compared to T1 images because of their edema (Fig. 8). Increased vascularity of the muscle causes enhancement when gadolinium is administered. Unlike CT, MR can more easily differentiate the optic nerve and subarachnoid fluid from adjacent extraocular muscles. V.

CONCLUSION

CT and MR imaging are complementary imaging modalities (13). Although there is considerable overlap in the diagnostic information provided by CT and MR, each modality also provides unique clinical information not afforded by the other. MR imaging provides superior soft tissue resolution. High signal intensity on noncontrast T2-weighted images suggests an acute phase of the disease, possibly amenable to treatment with corticosteroids or low-dose orbital radiation. CT provides detailed images of the bony anatomy necessary for formulating a surgical treatment plan REFERENCES 1. Hounsfield GN. Computed medical imaging. Nobel lecture, December 8, 1979. J Comput Assist Tomogr 1980; 4:115–119. 2. Hounsfield GN. Nobel Award address. Computed medical imaging. Med Phys 1980; 7:283– 290. 3. Rhea JT, Rao PM, Novelline RA. Helical CT and three-dimensional CT of facial and orbital injury. Radiol Clin North Am 1999; 37:489–513. 4. Nuyts J, De Man B, Dupont P, Defrise M, Suetens P, Mortelmans L. Iterative reconstruction for helical CT: a stimulation study. Phys Med Biol 1998; 43:729–737. 5. Lloyd GA. CT scanning in the diagnosis of orbital disease. Comput Tomogr 1979; 3:227– 239. 6. Feldon SE, Lee CP, Muramatsu SK, Weiner JM. Quantitative computed tomography of Graves’ ophthalmopathy. Arch Ophthalmol 1985; 103:213–215. 7. Kennerdell JS, Dresner SC. The nonspecific orbital inflammatory syndromes. Surv Ophthalmol 1984; 29:93–103. 8. Barrett L, Glatt HJ, Burde RM, Gado MH. Optic nerve dysfunction in thyroid eye disease: CT Radiology 1988; 167:503–507. 9. Rubin PA, Remulla HD. Surgical methods and approaches in the treatment of orbital disease. Neuroimaging Clin North Am 1996; 6:239–255. 10. De Marco JK, Bilaniuk LT. Magnetic resonance imaging: technical aspects. In: Newton TH, Bilaniuk LT, eds. Modern Neuroradiology, vol. 4. Radiology of the Eye and Orbit. San Anselmo, CA: Clavadel Press, 1990:1–14. 11. Harms SE. The orbit. In: Edelman RR, Hesselink JR, eds. Clinical Magnetic Resonance Imaging. Philadelphia: WB Saunders; 1990:598–603. 12. Weber AL, Dallow RL, Sabates NR. Graves’ disease of the orbit. Neuroimaging Clin N Am 1996; 6:61–72. 13. Muller-Forell W, Pitz S, Mann W, Kahaly GJ. Neuroradiological diagnosis in thyroid associated orbitopathy. Exp Clin Endocrinol Diabetes 1999; 107 Suppl 5:S177–S183.

31 Diagnostic Ultrasound in Graves’ Orbital Disease J. RANDALL HUGHES Center for Excellence in Eye Care, Miami, Florida, U.S.A.

Proptosis and diplopia are the most common indications for echographic evaluation of the orbit. Extraocular muscle evaluation is indicated for each of these, as is the search for an orbital tumor that would explain the proptosis. The diagnosis of thyroid eye disease (TED) is relatively easy for an experienced ophthalmic echographer skilled in orbital evaluation. Most orbital echography exams should include extraocular muscle evaluation. Asymmetrical abnormal muscle thickening in both orbits is the echographic benchmark of thyroid eye disease, and may be clearly evident on the initial screening with B-scan alone (1–4). However, TED findings can be subtle and may be revealed only with careful measurement of thickness and evaluation of muscle tissue reflectivity using diagnostic A-scan. Even when extraocular muscle appearance on B-scan is obviously consistent with thyroid eye disease, the findings and actual measurements should be confirmed with diagnostic A-scan.

I.

EVALUATING THE MUSCLES

Complete evaluation requires the combined use of a high-resolution (10 MHz) B-scan and diagnostic standardized A-scan. B-scans provide topographic information about muscle shape, general size, and, to some degree, internal reflectivity. Thickness of the muscle inserting tendon is also most efficiently assessed using B-scan. The B-scan images provide excellent topographic information. A-scan images provide more in-depth data about the internal structure of the muscle tissue and accurate measurement of thickness. Diagnostic

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A-scan is able to give repeatable and predictable spike amplitudes (internal reflectivity) from tissues with similar acoustic properties. These findings should be repeatable on other properly calibrated instruments. By using a calibrated decibel level (tissue sensitivity), meaningful reflectivity (amplitude of spike height) can be assessed reliably. Gaze fixation is important and should be similar for each eye in order to obtain reliable comparison between muscle pairs. Comparing a contracted muscle to one that is relaxed gives an inaccurate comparison of thickness and other anatomical properties. If motility of either eye is impaired, an attempt should be made to match the fixation of the eye with better mobility to the one with restricted movement, provided the deviation is not excessively off primary. A movable fixation light or other fixation point is extremely helpful to the patient in maintaining steady fixation. For the best resolution and most reliable evaluation a topical anesthetic is instilled in the eye and the probe is placed on the sclera rather than the lid. A gel such as methylcellulose is used on the face of the B-scan probe as a coupling medium. Liberal use of the gel makes excessive pressure on the eye unnecessary. In A-scan evaluation the probe face is small enough for the tear film to act as a natural coupling medium. A.

B-Scan

The B-scan sector can be directed through the ocular and orbital tissue in any orientation. The two most important orientations are referred to as longitudinal and transverse. Longitudinal scans show sections of tissue with an anterior/posterior orientation (anterior at the top of the screen and posterior at the bottom) and can be directed toward any meridian. For muscle evaluation the 12:00, 3:00, 6:00, and 9:00 meridians are used. The marker, located near the tip of the probe, relates to the top of the image on the screen and is oriented toward the cornea in longitudinal scans (Fig. 1A). The anterior two-thirds to three-quarters of each rectus muscle can be displayed using longitudinal scans. Transverse scans are oriented 90 degrees to longitudinal scan sections and cut across meridians (Fig. 1B). Transverse scans show oval cross sections of the rectus muscles. Serial sections through most of each muscle can be displayed by shifting the sound beam from posterior to anterior. The muscle should be centered in the image. By convention, the probe marker is directed nasally in horizontal, transverse scans through the superior and inferior orbital tissue, making anything above center on screen nasal to the muscle and anything below center temporal to the muscle. Transverse scans of the medial and lateral rectus muscles are vertical sections through the nasal and temporal orbital tissue and the probe marker is directed superiorly, making the top of the screen superior and bottom inferior to the muscle being examined. The general shape and thickness of each muscle is obtained using these two scan orientations. Orientations oblique to either of these may present confusing images and should usually be avoided. For evaluation of the superior rectus/levator complex, the patient should fixate slightly above primary gaze. The probe is placed on the sclera just posterior to the limbus at 6:00 with the marker oriented nasally. The sound beam is directed through the globe toward the superior orbit and is swept from anterior to posterior, displaying cross sections of the superior rectus and levator muscles from the superior rectus muscle insertion back to near the apex. Next, the muscles are evaluated longitudinally by rotating the probe marker 90 degrees so that it is directed toward the cornea, aligning the sound beam with the long axis of the muscle. This view shows the superior rectus from its insertion to its

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Figure 1 (A) B-scan probe position for a longitudinal scan of the medial rectus muscle. The probe face is on the sclera directly opposite the medial rectus and the marker is directed toward the cornea. (B) Gaze fixation and probe position are similar to A, except that the marker is now directed superiorly for the transverse scan. The muscles are marked by arrows in the corresponding echograms at the bottom.

more posterior extent all in one view. The levator can be identified separately from the rectus muscle by watching it slide over the rectus muscle as the patient blinks. The medial and lateral rectus muscles are evaluated similarly by placing the probe opposite the muscle being examined with fixation in primary or slightly toward the examined muscle. Fixation slightly toward the muscle being evaluated also gives more room for the probe face to be placed on the sclera and not the cornea. This is especially true when examining at the lateral rectus, because the bridge of the nose limits placement of the probe nasally. The inferior rectus is usually the most difficult to image, especially when it is not thickened. Having the patient fixate somewhat inferiorly and slightly nasally is helpful. The examiner may prefer placing the probe on the upper lid, rather than directly on the sclera. This approach is more comfortable for the patient, doesn’t degrade the image significantly, and often provides a better image of the inferior rectus. If there is moderate to severe proptosis or if the patient has shallow orbits, this technique may avoid proptosing the globe.

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A-Scan

A-scan evaluation of the extraocular muscles is difficult and requires considerable practice for the operator to feel confident in the measurements obtained. The technique of muscle evaluation with A-scan is similar to scanning the muscle with the transverse orientation of B-scan. The A-scan probe is positioned posterior to the limbus (Fig. 2), the sound beam is directed through the muscle, and the probe is angled to sweep the sound beam from anterior to posterior. Orbital soft tissue is highly reflective. Muscle tissue is somewhat more homogeneous, and has smaller interfaces making it less reflective. Because it is demarcated by the muscle sheath, it is possible to differentiate it from the surrounding orbital fat. Strong echoes are obtained from the muscle sheath when the sound beam is perpendicular to it. Using the B-scan probe orientation as a guide, a search is made for the high spikes from the muscle sheaths, and the examiner follows a roughly linear structure that runs in an anterior–posterior direction through the orbit (Fig. 3). Maintaining the sheath spikes as the sound beam is angled from anterior to posterior assures identification of the muscle rather than random highly reflective surfaces in the orbital tissue. The spacing between

Figure 2 Top photo shows the A-scan probe positioned on the sclera just posterior to the limbus inferiorly directing the sound beam through the superior rectus and levator muscles. Arrows show the location of the muscle sheath echoes in the A-scan echogram at the bottom.


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Figure 3 The approximate location along the muscle of the corresponding A-scan echograms at the bottom are labeled and indicated by arrows in the B-scan echogram at the top. The dip in the A-scan pattern from the muscle insertion is show by the single arrow in the bottom right echogram and the muscle sheaths are pointed out by arrows in the two right-hand echograms.

the sheath spikes will be small near the muscle insertion and increase as the muscle is traced posteriorly. Muscle thickness measurement should be recorded from the widest portion, the muscle belly. The distance between the muscle spikes is followed through the orbit and the image frozen at the widest point. Measurement should be performed perpendicular to the muscle’s long axis. Perpendicularity is shown by steep spikes from the sheaths that rise cleanly with minimal steps or nodes. Echo spikes with significant steps indicate an oblique orientation, which will produce an erroneous measurement. Muscles thickened by thyroid eye disease typically have long internal spikes that have high peaks separated by deep valleys. The reflectivity is usually medium to high and, at times, difficult to differentiate from surrounding orbital tissue with both A- and B-scan.

II. OTHER ORBITAL CHARACTERISTICS HELPFUL IN THE DIFFERENTIATION OF THYROID EYE DISEASE Other acoustic characteristics will help in differentiating thyroid eye disease from other orbital abnormalities. There is usually an increase in width of the orbital fat pattern and a common finding is a layer of reduced reflectivity from the periorbital region along the

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orbital wall (1,3). These are not usually evident in the normal orbit but are often seen in TED. When present they are most readily seen while performing B-scans of the medial and lateral rectus muscles. Orbital vessels are usually not evident during the screening exam on normal orbits. In Graves’ disease patients the most commonly identified dilated vessels are the medial collateral and superior ophthalmic veins. The medial collateral vein is located between the medial rectus and globe wall. It is displayed as a dark line in the transverse B-scan of the nasal orbit and as a dot or round echolucency in the longitudinal B-scan of the medial rectus. A roughly longitudinal section directed superonasaly best shows the superior ophthalmic vein, although the probe will have to be rotated around its axis to align the sweep of the sound beam along the vessel. It can also be shown as a dot or round

Figure 4 A- and corresponding B-scan echograms of normal extraocular muscles. The arrows in the B-scans on the right are in the approximate location along the muscle that the corresponding A-scans were obtained.


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echolucency in a transverse section through the superonasal orbital tissue. Abnormally dilated orbital vessels along with muscle thickening may also indicate congestion secondary to a lesion in the apex or from an intracranial process. Demonstration of disk elevation should be noted as well as any distention of the retrobulbar optic nerve sheaths. A longitudinal scan that includes the optic nerve head is used to rule out disc elevation. A transverse scan from temporal directed nasally and angled obliquely through the globe passing just temporal to the disc and cutting a crosssection of the anterior portion of the optic nerve will show any obvious thickening or distention of the sheath. The cross-section shows the nerve as a round, low reflective structure just behind the globe. Sheath distention is displayed as an abnormally large cross

Figure 5 Representative A- and corresponding B-scan echograms of muscles thickened by thyroid eye disease. As in Figure 4, the arrows in the B-scans on the right are in the approximate location along the muscle that the corresponding A-scans were obtained.

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Table 1 Upper Limits of Normal for Extraocular Muscles, and Acceptable Limits of Difference Between the Two Sides (mm) Maximum value

Acceptable difference between sides

3.9–6.8 2.2–3.8 1.6–3.6 2.3–4.7 11.9–16.9

0.8 0.4 0.4 0.5 1.2

Superior rectus/levator complex Lateral rectus Inferior rectus Medial rectus Sum of all muscles Source: Ref. 9.

section of the nerve or as an obvious area of low reflective fluid around the nerve, appearing as a crescent-shaped echolucency immediately distal to the nerve from the probe. Disc elevation can be caused by optic nerve head drusen, an optic nerve tumor, or papilledema. If there is marked muscle thickening, especially posteriorly, as can be seen in Graves’ disease, papilledema may result from crowding in the apex causing pooling of cerebrospinal fluid in the subarachnoid space (5). Marked, low reflective thickening of only one muscle without tendon involvement is highly suspicious for a tumor metastatic to the muscle (1,3,4,6). If there is tendon thickening with or without pain, myositis is the most likely cause (1,3,4,7,8). In either of these cases, secondary thickening of adjacent muscles may be present and the reflectivity will probably be higher than the primarily affected muscle. Assessment of the orbital soft tissue, orbital vessels, and the optic nerve requires familiarity with the normal appearance of these structures gained from experience evaluating normal orbits. For a comparison of echograms from normal extraocular muscles with those thickened by TED, see Figures 4 and 5. III. WHAT THE FINDINGS MEAN An analysis of muscle sizes, differences between the two orbits, and an evaluation of other echographic findings will often confirm or deny the probable diagnosis of thyroid eye Table 2 Echocardiographic Characteristics of Extraocular Muscles in TED and Other Orbital Diseases Marked, medium to high reflective, asymmetrical thickening of multiple muscles with normal insertions Minimal, asymmetrical thickening of 3 or more muscles Zero to two muscles thickened (minimally) High reflective thickening of three or four muscles unilaterally Low reflective thickening of one muscle sparing the tendon Low reflective thickening of one or more muscles with tendon involvement

Typical for TED

Suspicious for TED—suggest follow-up Normal orbital findings Possibly unilateral TED, but consider orbital congestion Rule out metastatic lesion vs. myositis involving only the muscle belly Most consistent with myositis


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disease. Once the B-scan echograms and reliable A-scans are in hand, the hard part is done. Table 1 gives the upper size limits (95% confidence level) of normal muscle thickness. Table 2 is a guide to help interpretation of the findings. REFERENCES 1. Byrne SF, Green RL. Ultrasound of the Eye and Orbit. St. Louis: Mosby Year Book, Inc., 1992: 372–378. 2. Delent PJ, Mourits MP, Kerlen CH, Scheenloop JJ, Wittbol-Post D. B-scan ultrasonography in Graves’ orbitopathy. Doc Ophthamol 1993; 85:1–4. 3. Dutton JJ, Byrne SF, Proia AD. Diagnostic Atlas of Orbital Diseases. Philadelphia: WB Saunders, 2000:150–151. 4. DiBernardo C, Schachat AP, Fekrat S. Ophthalmic Ultrasound—A Diagnostic Atlas. Stuttgart: Thieme, 1998:124. 5. Barrett L, Glatt HJ, Burde RM, Gado MH. Optic nerve dysfunction in thyroid eye disease. Radiology 1988; 167(2):503. 6. DiBernardo C, Pacheco EM, Hughes JR, Hiff WJ, Byrne SF. Echographic evaluation and findings in metastatic melanoma to extraocular muscles. Ophthalmology 1996; 103(11):1794–1797. 7. Siatkowski RM, Capo H, Byrne SF, Gendron EK. Clinical and echographic findings in idiopathic orbital myositis. Am J Ophthalmol 1994; 118:343–350. 8. Scott IU, Siatkowski RM. Idiopathic orbital myositis. Curr Opin Rheumatol 1997; 9:504–512. 9. Byrne SF, Gendron EK, Glaser JS, Feuer W, Atta H. Diameter of normal extraocular recti muscles with echography. Am J Ophthalmol 1991; 112:706–713.

32 Glaucoma in Thyroid Eye Disease JOHN S. KING and PETER A. NETLAND University of Tennessee Health Science Center, Memphis, Tennessee, U.S.A.

I.

INTRODUCTION

An early description of glaucoma associated with thyroid disease was reported by Brailey and Eyre in the Guy’s Hospital Reports in 1897 (1). Although most reports in the literature do not support a causal relationship between glaucoma and Graves’ disease, elevated intraocular pressure has been associated with Graves’ ophthalmopathy. In 1918, the German ophthalmologist, Karl Wessely first described this association (2). In 1953, Braley contributed further by discovering an increased number of patients in this population exhibiting elevated intraocular pressure in upgaze compared with primary gaze (3). II. MECHANISMS Increased intraocular pressure on upgaze is associated with fibrosis of the inferior rectus muscle, which is the most commonly affected muscle in the chronic form of Graves’ ophthalmopathy (4,5). When the antagonist muscles attempt to pull the eye upward, fibrosis of the inferior rectus muscle causes restriction in upgaze and mechanical compression of the globe, which is the presumed mechanism for increased intraocular pressure. Widely varying prevalence rates have been reported for increased intraocular pressure on upgaze among Graves’ disease patients, ranging from 22 to 76% (6–8). Increased intraocular pressure on upgaze is also found in normal individuals (9,10); thus it is a finding that has poor sensitivity in identifying individuals with Graves’ ophthalmopathy (10). Elevated episcleral venous pressure has been identified in patients with thyroid eye disease (11), and may contribute to the raised intraocular pressure in some patients. In

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Table 1 Prevalence (%) of Ocular Hypertension in Patients with Graves’ Disease and in the General Population

Ohtsuka and Nakamura (23) (n ⫽ 104) prospective Kalmann and Mouritt (22) (n ⫽ 482) Cockerham et al. (15) (n ⫽ 500)

Graves’ disease (%)

General population (%)

22

1.37

3.9

1.6

24

5

the chronic phase of Graves’ ophthalmopathy, there may be marked orbital infiltrative congestion characterized by hypertrophy of the extraocular muscles and orbital fat (12). This congestion may raise the retrobulbar pressure to levels that can compress more compliant structures such as the ophthalmic veins, and lead to raised episcleral venous pressure and, hence, elevated intraocular pressures (4,5). Other mechanisms may contribute to the elevated intraocular pressure observed in patients with Graves’ disease. These patients may accumulate mucopolysaccharide deposits in the aqueous outflow network, which could reduce the outflow facility and lead to increased intraocular pressures (13). It has been reported that corneal exposure can cause a severe anterior chamber reaction, which in turn may cause peripheral anterior synechiae formation associated with glaucoma (4,13,14). III. RELATIONSHIP BETWEEN GRAVES’ DISEASE AND OCULAR HYPERTENSION OR GLAUCOMA The association between Graves’ disease and elevated intraocular pressure has been demonstrated in several studies (15–23) (Table 1). In a prospective study of 104 consecutive Japanese patients with Graves’ disease, 22% (23 patients) had ocular hypertension, which is higher than the 1.37% prevalence of ocular hypertension in the general Japanese population (23). A retrospective study of 482 patients with Graves’ ophthalmopathy showed 3.9% with ocular hypertension compared with 1.6% in the general population (22). A retrospective study of 500 consecutive patients with thyroid-associated ophthalmopathy from Pittsburgh’s Allegheny General Hospital showed 24% with ocular hypertension compared with 5% in the general public (15). The prevalence of ocular hypertension in patients with Graves’ disease has been found to range between 5 and 15% (16–20). Some studies have found positive correlation between the degree of proptosis and the level of ocular tension (24). In contrast, several studies have found no increased prevalence of ocular hypertension in patients with Graves’ disease compared with the general population (25–27). The prevalence of open-angle glaucoma in patients with Graves’ disease is similar to that in the general population (15,22,26). In a study of 500 patients with thyroid eye

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disease, only 7 patients were classified as glaucoma subjects, and 2 patients showed progressive visual field abnormalities and cupping (15). However, a prospective Japanese study found a higher prevalence of open-angle glaucoma in patients with Graves’ disease than would be expected based on comparison to the general population in Japan (23).

IV.

CLINICAL EXAMINATION

During the clinical examination of patients with thyroid eye disease, there are some unique points to consider. Applanation tonometry may be performed in primary gaze, upgaze, and downgaze. With fibrosis of the inferior rectus muscles, intraocular pressure may be lower in downgaze and elevated in upgaze. A greater than 2 mmHg increase on upgaze is often considered abnormal; however, healthy individuals may show an increased intraocular pressure of 4–6 mmHg in different gaze positions (9). It may be helpful to note an increased intraocular pressure in upgaze, but this finding is nonspecific in patients with thyroid eye disease (10). Raised episcleral venous pressure is characterized by dilated, tortuous episcleral veins. Measurement of episcleral venous pressure is not commonly performed clinically. However, observation of dilated and congested episcleral vessels should be noted. Optic nerve examination should be performed to assess the size, appearance, and integrity of the optic disc. Visual fields should be performed to correlate the appearance of the optic nerve with glaucomatous visual field defects. On the other hand, in particular with optic neuropathy due to Graves’ disease, the appearance of the optic nerve may be normal or disc edema may be found (28). In general, the appearance of the visual field does not correlate well with optic nerve appearance in compressive or infiltrative optic neuropathy due to thyroid eye disease.

V. MANAGEMENT Management of elevated intraocular pressure in patients with concomitant glaucoma and thyroid ophthalmopathy may be influenced by the treatment of the thyroid eye disease. Corticosteroid therapy may suppress orbital inflammation, which may have a beneficial effect on intraocular pressure (5), although chronic steroid therapy may contribute to a rise in intraocular pressure (29). A number of studies demonstrate a significant reduction in intraocular pressure after decompression of the orbit (14,22,24). Furthermore, Kallman documented two cases in which patients with Graves’ orbitopathy and elevated intraocular pressure showed a marked reduction in intraocular pressure, after recession of the inferior rectus muscles (22). He also noted that five patients with Graves’ orbitopathy and ocular hypertension showed a permanent decrease in intraocular pressure after orbital decompression (22). A retrospective evaluation of 12 consecutive patients (22 eyes) with thyroid orbitopathy who underwent surgical decompression showed significantly lower intraocular pressure postoperatively than preoperatively. These results were attributed to the reduction in orbital pressure and subsequent reduction of episcleral venous pressure (14). Algvere reported that three of five patients with both thyroid eye disease and intraocular pressures of 28 mmHg or higher, which were all refractory to medical therapy, showed remarkably lower intraocular pressures not requiring further medical therapy after orbital decompres-

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sion was performed (17). Orbital decompression surgery should be performed, when necessary, before consideration of surgical procedures for the correction of glaucoma. A.

Medical Management of Elevated Intraocular Pressure

Gaze-dependent ocular hypertension should be differentiated from sustained pressures in any direction of gaze. Treatment is usually not indicated for infiltrative ophthalmopathy with elevated intraocular pressure in some gaze positions. However, patients with sustained high ocular tension, especially in primary gaze position, may require treatment. Topical antiglaucoma medications should be the first line of approach, in particular aqueous suppressants. In patients with elevated episcleral venous pressure, cholinergic drugs may have minimal effects; aqueous humor suppression using beta-adrenergic blockers, alpha-adrenergic blockers, and carbonic anhydrase inhibitors may yield better results. Prostaglandin analogues may be associated with ocular inflammation, which should be avoided during the acute congestive phase of thyroid ophthalmopathy. B.

Surgical Intervention

Laser trabeculoplasty may not be effective in lowering intraocular pressure associated with elevated episcleral venous pressure. Filtration surgery with adjunctive antifibrosis drugs is an effective and commonly used treatment for patients with glaucoma that has failed to respond to medical and laser therapy. However, patients with Graves’ ophthalmopathy associated with elevated episcleral venous pressure may have an increased risk for choroidal effusion and suprachoroidal hemorrhage (30). These complications can be minimized with tight closure of the scleral flap with releasable sutures or the use of postoperative laser suture lysis. Cyclophotocoagulation may provide an alternative to filtration surgery in some cases in which elevated intraocular pressure is secondary to elevated episcleral venous pressure. VI.

HYPOTHYROIDISM

In 1920, Hertel noted an association between hypothyroidism and primary open-angle glaucoma in two patients (31). Since that time, other case reports and studies have found an association of hypothyroidism with primary open-angle glaucoma (32–35). Myxedema is a severe form of hypothyroidism in which, through autoimmune processes, mucopolysaccharides accumulate in the ground substance of various tissues. It has been suggested that the trabecular meshwork could be obstructed through this mechanism (32,36). Hypothyroid patients have been found to have reduced facility of outflow, which improved with treatment of the hypothyroid state (33,37). Others have found no evidence of an association with hypothyroidism and primary open-angle glaucoma (27,38). Some early reports note an association between hypothyroidism and a high–normal elevated intraocular pressure (31,39–42). Other studies, however, have not shown the same relationship (26,27,43). VII.

CONCLUSION

Elevated intraocular pressure is more commonly found in patients with thyroid eye disease than in the general population. However, definite glaucomatous progressive changes of the

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optic nerve and visual fields are probably no more common than in the general population. Treatment for Graves’ orbitopathy, particularly orbital decompression, may have a beneficial effect on the intraocular pressure. Patients with elevated intraocular pressure should be monitored for optic nerve and visual field changes. Medical antiglaucoma therapy may be required, but surgical treatment for glaucoma is not necessary in the majority of patients with thyroid ophthalmopathy and elevated intraocular pressure.

REFERENCES 1. Brailey WA, Eyre JWH. Guy’s Hosp Rep 1897; 54:65. 2. Wessely K. Discussion of Weiterer Beitrag zur Lehre von Augendruck. Berl Zusammenkunft Dtsch Ophthalmol Ges 1918; 41:80–81. 3. Braley AE. Malignant exophthalmos. Am J Ophthalmol 1953; 36:1286–1290. 4. Piltz-Seymour JR, Stone RA. Glaucoma associated with systemic disease. In: Rich R, Shields MB, Krupin T, eds. The Glaucomas, 2nd ed. St. Louis: Mosby, 1996:1157–1176. 5. Weinreb RN, Karwatowski WSS. Glaucoma associated with elevated episcleral venous pressure. In: Rich R, Shields MB, Krupin T, eds. The Glaucomas, 2nd ed. St. Louis: Mosby, 1996: 1143–1155. 6. Allen C, Stetz D, Roman SH, Podos S, Som P, Davies TF. Prevalence and clinical associations of intraocular pressure changes in Graves’ disease. J Clin Endocrinol Metab 1985; 61(1):183– 187. 7. Gamblin GT, Harper DG, Galentine P, Buck DR, Chernow B, Eil C. Prevalence of increased intraocular pressure in Graves’ disease—evidence of frequent subclinical ophthalmopathy. N Engl J Med 1983; 308:420–424. 8. Gamblin GT, Galentine P, Chernow B, Smallridge RC, Eil C. Evidence of extraocular muscle restriction in autoimmune thyroid disease. J Clin Endocrinol Metab 1985; 61(1):167–171. 9. Reader AL. Normal variations of intraocular pressure on vertical gaze. Ophthalmology 1982; 89(9):1084–1087. 10. Spierer A, Einstein Z. The role of increased pressure on upgaze in the assessment of Graves’ ophthalmopathy. Ophthalmology 1991; 98:1491–1494. 11. Jorgensen JS, Guthoff R. Die Rolle des episkleralen Venendrucks bei der Entstehung von Sekundar-glaukomen. Klin Monatsbl Augenheilkd 1988; 193(5):471–475. 12. Dallow RL, Netland PA. Management of thyroid ophthalmology (Graves’ disease). In: Albert DM, Jakobiec FA, eds. Principles and Practice of Ophthalmology, Vol. 3. Philadelphia: WB Saunders, 1994:1905–1922. 13. Higginbotham EJ. Glaucoma associated with increased episcleral venous pressure. In: Albert DM, Jakobiec FA, Azar DT, Gragoudas E, Power SM, Robinson NL, eds. Principles and Practice of Ophthalmology, 2d ed. Philadelphia: WB Saunders, 2000:2781–2792. 14. Dev S, Damji KF, DeBacker CM, Cox TA, Dutton JJ, Allingham RR. Decrease in intraocular pressure after orbital decompression for thyroid orbitopathy. Can J Ophthalmol 1998; 33:314– 319. 15. Cockerham KP, Pal C, Jani B, Wolter A, Kennerdell JS. The prevalence and implications of ocular hypertension and glaucoma in thyroid-associated orbitopathy. Ophthalmology 1997; 104:914–917. 16. Manor RS, Kurz O, Lewitus Z. Intraocular pressure in endocrinological patients with exophthalmos. Ophthalmologica 1974; 168:241–252. 17. Algvere P, Almqvist S, Backlund EO. Pterional orbital decompression in progressive ophthalmopathy of Graves’ disease: 1. Short-term effects. Acta Ophthalmol (Copenh) 1973; 51: 461–474.

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18. Vanni V, Vozza R. Behavior of the ocular tension in exophthalmos. Bol Ocul 1960; 39:189– 197. 19. Haddad HM. Tonography and visual fields in endocrine exophthalmos. Report on 29 patients. Am J Ophthalmol 1966; 61:997–999. 20. Aron-Rosa D, Morax PV, Aron JJ, Metzger J. Endocrine edematous exophthalmos and orbital venous circulatory blocking. Value of phlebography. Ann Ocul (Paris) 1970; 203: 1–24. 21. Hoskins HD, Kass MA. Secondary open-angle glaucoma. In: Hoskins HD, Kass MA, eds. Becker-Shaffer’s Diagnosis and Therapy of the Glaucomas, 6th ed. St. Louis: CV Mosby, 1989:308–350. 22. Kalmann R, Mourits MP. Prevalence and management of elevated intraocular pressure in patients with Graves’ orbitopathy. Br J Ophthalmol 1998; 82:754–757. 23. Ohtsuka K, Nakamura Y. Open-angle glaucoma associated with Graves disease. Am J Ophthalmol 2000; 129:613–617. 24. Ohtsuka K, Nakamura Y. Intraocular pressure and proptosis in 95 patients with Graves’ ophthalmopathy. Am J Ophthalmol 1997; 124(4):570–572. 25. Bock VJ, Stepanik J. Glaukom bien thyreogenem exophthalmus. Ophthalmologica 1961; 142: 365. 26. Cheng H, Perkins ES. Thyroid disease and glaucoma. Br J Ophthalmol 1967; 51:547–553. 27. Pohjanpelto P. The thyroid gland and intraocular pressure. Acta Ophthalmol Suppl (Copenh) 1968; 97:1–70. 28. Netland PA, Dallow RL. Thyroid ophthalmology. In: Albert DM, Jakobiec FA, eds. Principles and Practice of Ophthalmology, Vol. 5. Philadelphia: WB Saunders, 1994:2937– 2953. 29. Carnahan MC, Goldstein DA. Ocular complications of topical, peri-ocular, and systemic corticosteroids. Curr Opin Ophthalmol 2000; 11(6):478–483. 30. Bellows AR, Chylack LT, Epstein DL, Hutchinson BT. Choroidal effusion during glaucoma surgery in patients with prominent episcleral vessels. Arch Ophthalmol 1979; 97:493– 497. 31. Hertel G. Eineges uber der Augendruck und Glaukom. Klin Monatsbl Augenheilkd 1920; 64: 390–392. 32. Smith KD, Arthus BP, Saheb N. An association between hypothyroidism and primary openangle glaucoma. Ophthalmology 1993; 100:1580–1584. 33. Smith KD, Tevaarwerk GJM, Allen LH. Reversal of poorly controlled glaucoma on diagnosis and treatment of hypothyroidism. Can J Ophthalmol 1992; 27(7):345–347. 34. Carenini BB, Mignone U, Vadala G, Gastaldi C, Favero C, Brogliatti B. Glaucoma and hypothyroidism. Acta Ophthalmol Scand 1997:47–48. 35. Cartwright MJ, Grajewski AL, Friedberg ML, Anderson DR, Richards DW. Immune-related disease and normal-tension glaucoma. A case–control study. Arch Ophthalmol 1992; 110(4): 500–502. 36. Boles CB, Mignone U, Vadala G, Gastaldi C, Favero C, Brogliatti B. Glaucoma and hypothyroidism. Acta Ophthalmol Scand 1997; 224:47–48. 37. Hertel E. Weiterer Beitrag zur Lehre von Augendruck. Berl Dtsch Ophthal Ges 1918; 41:57– 61. 38. Gillow JT, Shah P, O’Neill EC. Primary open angle glaucoma and hypothyroidism: chance or true association? Eye 1997; 11(1):113–114. 39. Terrien F. Troubles visuels et alterations des glandes a` secretion interne. Arch Ophthalmol (Paris) 1922; 39:716–741. 40. Freytag GT. Eber den Augendruck bei Storungen der inneren Sekretion. Klin Monatsbl Augenheilk. 1924; 72:515–522. 41. Plicquet J. Etude e´xperimentale et clinique de l’action de la thyroide sur la tension oculaire.

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Rapports de la fonction thyroidienne avec le glaucomae. Bull Soc Ophthal (Paris) 1929; 1: 12–39. 42. Larsen V. Le metabolisme basal chez les glaucomateux. Acta Ophthal (Kobenhavn) 1933; 11: 494–500. 43. Salvati G. Sulla disfunzione della tiroide e la tensione oculare. G Oculist 1928; 9(5): 54–56.

33 Optic Neuropathy in Thyroid Eye Disease RICHARD D. DREWRY, Jr. University of Tennessee Health Science Center, Memphis, Tennessee, U.S.A.

Changes of vision occur commonly in patients with Graves’ disease, with a number of vision complaints due to corneal epithelial disruption or tear film changes (1). The most serious complication of Graves’ ophthalmopathy is visual impairment from optic neuropathy. The clinician must be diligent in screening for optic nerve involvement in patients with severe thyroid eye disease, since the most common cause of permanent vision loss is optic neuropathy. I.

CLINICAL FINDINGS

Optic nerve involvement occurs in 5–8% of patients with Graves’ disease (2,3). The age of involved patients is typically 40–80 years, and most studies have not found a gender predilection. A study by Neigel and co-workers (3) suggested that patients with optic neuropathy complicating thyroid ophthalmopathy were more frequently male, had a later onset of thyroid disease, and were more frequently diabetic. Many patients note blurring or graying of vision suggesting optic nerve involvement; however, the visual symptoms may be subtle but progressive. Although patients may not voluntarily describe color loss, this symptom may be present upon questioning. Neigel et al. (3) found that in nearly half of their patients neither the referring physician nor the patient was aware of early signs of optic neuropathy. These patients usually exhibit other features of thyroid ophthalmopathy, such as proptosis, eyelid retraction, increased intraocular pressure in upgaze, restrictive ocular myopathy, and soft tissue signs of inflammation. These other features may obscure symptoms of visual impairment, making it difficult for the physician and patient to recognize the insidious onset of optic neuropathy. Visual acuity may be near normal in a significant number of patients, although other signs of optic neuropathy will be present (3). 327

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Early detection of optic nerve dysfunction is important. Since visual acuity may remain good in many cases, examination should include assessment of pupil function, color vision, and threshold visual field, in addition to observation of the optic disks. Although visual defects will be present in both eyes in the majority of patients, complaints may be referred to one eye (2). If the optic nerve involvement is asymmetrical, a relative afferent pupil defect may be present. II. VISUAL TESTING Color vision testing may reveal relative dyschromatopsia in patients with optic neuropathy of Graves’ disease (3,4). Trobe and Glaser (2) noted that Ishihara color plate testing was clearly abnormal only in association with visual acuity below 20/40. The FarnsworthMunsell 100 hue test of color discrimination is a sensitive indicator of optic nerve dysfunction and may be useful if compressive optic neuropathy is suspected (5). An abnormal threshold visual field examination is a more sensitive indicator of optic neuropathy than is reduced visual acuity. A number of visual field abnormalities have

Figure 1 Threshold visual field of the left eye with an inferior nerve fiber bundle defect caused by compressive optic neuropathy of Graves.

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Figure 2 Moderate disk edema and peripapillary nerve fiber layer hemorrhage of the right eye in a patient with optic neuropathy of Graves.

been described, including central scotoma, paracentral scotoma, arcuate and nerve fiber bundle defects, increased blind spot size, and generalized constriction (2,3) (Fig. 1). Threshold visual field is recommended in routine screening of patients with severe Graves’ disease and in those patients who present with visual symptoms. The optic disk may appear entirely normal in thyroid optic neuropathy. Changes include mild or marked disc edema (Figs. 2, 3) and pallor, which have been observed in approximately half of affected patients (2,3,6). No special features of the optic disk swelling are considered pathognomonic for compressive optic neuropathy. Congestive signs and evidence of ocular myopathy almost always precede visual loss, which is often bilateral,

Figure 3 Moderate disk edema of the left eye in a patient with optic neuropathy of Graves.

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symmetrical, and gradual in onset. Presentation may be limited to one eye in 24–40% of cases (2,6,7). Electrophysiological evidence of compressive thyroid optic neuropathy may be provided by a visual evoked potential (VEP). VEP abnormality, specifically prolonged P100 latency, is a sensitive indicator of an optic nerve conduction defect, which may be documented in more than 90% of patients (3,8). The VEP abnormality may be present in patients without subjective vision complaints or clinical evidence of optic neuropathy (9). III. PATHOGENESIS The pathogenesis of thyroid optic neuropathy remains somewhat controversial, but it is most likely related to mechanical compression of the optic nerve at the orbital apex (6). Inflammatory cellular infiltration, mucopolysaccharide deposition, and interstitial edema develop in the orbital tissues, including the extraocular muscles (10). Compression of the optic nerve may result from increased intraorbital pressure resulting from these changes, or to thickening of the extraocular muscles at the orbital apex, where the limited crosssectional area may add to a compressive effect (11). Either direct damage or indirect damage through an ischemic effect may result from mechanical compression of the optic nerve (2). Trokel and Jakobiec (11) noted that compression from enlarged extraocular muscles can lead to impedance of venous drainage of the orbit and thereby cause venous stasis and orbital congestion. Nugent et al. (12) demonstrated an enlarged superior ophthalmic vein that they found to be more common in orbits with concomitant optic neuropathy. They interpreted this as a reflection of apical compression by the enlarged extraocular muscles. Recent advances in imaging techniques have greatly improved visualization of the pathological soft tissue changes of thyroid ophthalmopathy. Standard A-scan ultrasonography notes enlargement of the bellies of the extraocular muscles with the insertions relatively spared. A medium to highly reflective internal interface within the muscles is characteristic of Graves’ disease (13). B-scan ultrasound documents the qualitative increase in the diameter of the muscles; however, muscle enlargement at the apex of the orbit is difficult to assess (6). Ultrasonography may also demonstrate evidence of optic nerve enlargement with increased subarachnoid fluid surrounding the anterior portion of the optic nerve (14,15). Computed tomographic (CT) scanners are capable of generating two-dimensional images with high resolution and minimal volume averaging. Axial and coronal scans should be obtained in patients with severe thyroid eye disease who are suspected of having optic neuropathy. Enlargement of the extraocular muscles with relative sparing of the tendinous insertion is the most frequent finding (Fig. 4). Coronal views frequently document enlarged extraocular muscles converging at the crowded orbital apex with compression of the optic nerve (Fig. 5) (11). Neigel and co-workers (3) noted apical crowding of moderate or severe nature in 79.2% of patients with thyroid optic neuropathy. In more than half of these patients the optic nerve appearance at or near the orbital apex was flattened or decreased in size secondary to compression from the enlarged extraocular muscles. Other findings noted on CT scans include proptosis, prominence of orbital fat, anterior displacement of the lacrimal glands, dilated superior ophthalmic vein, and stretching of the optic nerve (3,6,11,16). Some investigators have determined that proptosis is not helpful in assessing the risk of optic neuropathy, but rather extraocular muscle volume shown by limitation of


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Figure 4 Axial CT scan of the orbit. The medial and lateral rectus muscles are enlarged but the tendon is relatively spared. The enlarged muscles contact the optic nerve in the left orbital apex. ocular motility and enlargement on CT scanning has the higher correlative value (6,17). Neigel and co-workers (3) noted that severe proptosis was one of the CT findings, which should alert the clinician to the presence of a possible optic neuropathy. In addition to severe proptosis, other factors were severe apical crowding, increased muscle diameter index, dilated superior ophthalmic vein, and anterior displacement of the lacrimal gland. Magnetic resonance imaging (MRI) is a newer imaging technique, which does not require ionizing radiation. The major advantage of MRI is improved differentiation of adjacent tissues. Bone and tooth artifacts that interfere with CT image quality are less of

Figure 5 Coronal CT scan of the orbit. The enlarged extraocular muscles are compressing the optic nerve.

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a factor with MRI. However, MRI scans are more expensive, less readily available, and take a longer period of time. Optimal orbital scans are obtained by the use of a surface coil with fat suppression. IV.

THERAPY

Although spontaneous remission of untreated thyroid optic neuropathy has been reported with a favorable outcome, nearly one-quarter of reported patients remain severely visually impaired (18). Previously reported series of patients with thyroid optic neuropathy (2,7,19) indicated that oral systemic corticosteroid therapy could be of benefit, although relapses occurred in a significant number of patients as the corticosteroid dosage was lowered. The mechanism for steroid therapy is uncertain, although the anti-inflammatory and immunesuppressive actions are probably the most important. There are no firm guidelines to systemic steroid dosage in thyroid optic neuropathy. Most clinicians prescribe oral corticosteroids in dosages of 60–100 mg/day prednisone for 2–4 weeks, with a gradual tapering by 5–10 mg/day every 1–2 weeks. Trobe and associates (2) noted that if a response to oral corticosteroids was to occur at all, signs of improvement in visual function were evident within 1 week or earlier. They considered that there was no apparent justification for maintaining patients with optic neuropathy on prolonged corticosteroid therapy in the absence of improvement. If an observable response has not occurred within 3 weeks, continued high dosage is not likely to be successful. Some clinicians have advocated intravenous methylprednisolone in dosages similar to those given patients with other autoimmune diseases, such as lupus erythematosus. Methylprednisolone, 500 mg–1.0 g daily for 3 days, may be used. This therapy may provide a more rapid response of thyroid optic neuropathy that may be sustained by a tapering regimen of oral corticosteroids and/or orbital irradiation (20). The efficacy of oral prednisone, as compiled by Wiersinga from eight studies published between 1955 and 1993, was 65% (21). In patients with poor response to therapy, with considerable side effects to therapy, or requiring high-dosage corticosteroids for control, alternative radiation therapy or surgery should be considered. Almost all patients on long-term corticosteroid therapy experience side effects, which limit the duration of therapy. If radiation or surgery is considered, the corticosteroid may be continued and its dosage tapered during and following radiation therapy or in the postoperative period. A.

Radiation

External beam irradiation should be considered for patients with thyroid optic neuropathy in whom corticosteroids are contraindicated, for those who experience significant side effects from corticosteroids, and for those who are nonresponsive after an adequate trial. Patients who require surgical decompression for thyroid optic neuropathy and whose inflammatory features continue may also be candidates for radiation therapy (22). Although it is not clear why radiation therapy is effective in Graves’ disease, it may be that there is a differential effect on helper and suppressor T lymphocytes. Whether radiation therapy is simply an immunosuppressive mediator affecting specific lymphocytes or acts by diminishing the inflammatory response nonspecifically is still unknown (22). The recommended dose of radiation is 2000 cGy. An oral corticosteroid may be continued, at least during the first 2 weeks of radiation therapy. A response should be evident within 2 weeks of completion of therapy, and progressive neuropathy 4 weeks or


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more after radiation indicates a need for alternative therapy (23). Radiation is not indicated for patients with coexistent diabetic retinopathy or with previous cranial radiation. Kazim reported that 95% of patients treated for thyroid optic neuropathy with radiation experienced improvement. Only 1 of 29 patients treated with radiotherapy required surgical decompression (1). Rush and colleagues reported improvement in optic nerve function in 8 of 10 patients during radiotherapy (2000 cGy in 10 fractions) or within 2 weeks of completion (24). B.

Surgical Decompression

Garrity and co-workers (25) have noted that primary therapy of thyroid ophthalmopathy is directed toward resolution of the volume to space discrepancy. The volume to space discrepancy can be resolved medically by shrinkage of soft tissues with corticosteroids or radiation or by expanding the orbital volume surgically to accommodate the swollen tissue. The value of surgical decompression in preserving vision in patients with thyroid optic neuropathy has been documented in several studies (25–29). However, prognosis for vision return in such patients with chronic poor vision is guarded after any form of therapy (30). In patients with compressive optic neuropathy unresponsive to corticosteroid therapy and/or radiation therapy, surgical decompression is recommended, unless there is an absence of clinical and CT evidence of enlarged extraocular muscles and optic nerve compression. In patients with rapid (less than 1 week) vision loss, relatively rapid progression of vision loss to less than 20/200, or marked vision loss secondary to rapid proptosis, emergent decompression with simultaneous high-dosage systemic steroid therapy should be considered (30). Orbital decompression can relieve the apical compression and offer a more rapid response than medical or radiation therapy. Response can be measured postoperatively by improvement in visual acuity and improvement or resolution of visual field defects and dyschromatopsia. Disk edema observed preoperatively should resolve (25). Since surgical decompression does not affect the cause of inflammation or fibrosis of thyroid ophthalmopathy, these patients may require further treatment in the postoperative period to preserve vision. McCord noted that 27% of patients required additional therapy after surgical decompression and 20% required supplemental steroids or irradiation (27). REFERENCES 1. Kazim M, Trokel S, Moore S. Treatment of acute Graves’ orbitopathy. Ophthalmology 1991; 98:1443–1448. 2. Trobe JD, Glaser JS. Dysthyroid optic neuropathy. Clinical profile and rationale for management. Arch Ophthalmol 1978; 96:1199–1209. 3. Neigel JM, Rootman J, Belkin RI, Nugent RA, Drance SM, Beattie CW, Spinelli JA. Ophthalmology 1988; 95:1515–1521. 4. Carter KD, Frueh BR, Hessburg TP, Musch DC. Long-term efficacy of orbital decompression for compressive optic neuropathy of Graves’ eye disease. Ophthalmology 1991; 98:1435– 1442. 5. Nichols BE, Thompson HS, Stone EM. Evaluation of a significantly shorter version of the Farnsworth-Munsell 100-hue test in patients with three different optic neuropathies. J NeuroOphthalmol 1997; 17:1–6. 6. Kennerdell JS, Rosenbaum AE, El-Hoshy MH. Apical optic nerve compression of dysthyroid optic neuropathy on computed tomography. Arch Ophthalmol 1981; 99:807–809.

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7. Day RM, Carroll FD. Optic nerve involvement associated with thyroid dysfunction. Arch Ophthalmol 1962; 67:289–297. 8. Tsaloumas MD, Good PA, Burdon MA, Misson GP. Flash and pattern visual evoked potentials in the diagnosis and monitoring of dysthyroid optic neuropathy. Eye 1994; 8:638–645. 9. Salvi M, Spaggiari E, Neri F, Macaluso C, Gardini E, Ferrozzi F, Minelli R, Wall JR, Roti E. The study of visual evoked potentials in patients with thyroid-associated ophthalmopathy may identify asymptomatic optic nerve involvement. J Clin Endocrinol Metab 1997; 82(4): 1027–1030. 10. Kroll AJ, Kuwabara T. Dysthyroid ocular myopathy: anatomy, histology, and electron microscopy. Arch Ophthalmol 1966; 76:244–257. 11. Trokel SI, Jakobiec FA. Correlation of CT scanning and pathologic features of ophthalmic Graves’ disease. Ophthalmology 1981; 88:553–564. 12. Nugent RA, Belklin RI, Neigel JM, Rootman J, Robertson WE, Spinelli J, Graeb DA. Graves’ orbitopathy. Correlation of CT and clinical findings. Radiology 1990; 177(3):675–682. 13. Ossoinig KC. Ultrasonic diagnosis of Graves’ ophthalmopathy. In: Gorman CA, Waller RR, Dyer JA, eds. The Eye and Orbit in Thyroid Disease. New York: Raven Press, 1984:185– 211. 14. Coleman DJ, Jack RL, Franzen LA, Werner SC. High resolution B-scan ultrasonography of the orbit. V. Eye changes of Graves’ disease. Arch Ophthalmol 1972; 88:465–471. 15. Skalka HW. Perineural optic nerve changes in endocrine orbitopathy. Arch Ophthalmol 1978; 96:468–473. 16. Trokel SL, Hilal SK. Recognition and differential diagnosis of enlarged extraocular muscles in computed tomography. Am J Ophthalmol 1979; 87:503–512. 17. Feldon SE, Muramatsu S, Weiner JM. Clinical classification of Graves’ ophthalmopathy. Arch Ophthalmol 1984; 102:1469–1472. 18. Panzo GJ, Tomsak RL. A retrospective review of 26 cases of dysthyroid optic neuropathy. Am J Ophthalmol 1983; 96:190–194. 19. Brown J, Coburn JW, Wigod RA, Hiss JM Jr, Dowling JT. Adrenal steroid therapy of severe infiltrative ophthalmopathy of Graves’ disease. Am J Med 1963; 34:786–795. 20. Guy JR, Fagien S, Donovan JP, Rubin ML. Methylprednisolone pulse therapy in severe dysthyroid optic neuropathy. Ophthalmology 1989; 96:1048–1052. 21. Wiersinga WM. Advances in medical therapy of thyroid-associated ophthalmopathy. Orbit 1996; 15:177–186. 22. Brennan MW, Leone CR Jr, Janaki L. Radiation therapy for Graves’ disease. Am J Ophthalmol 1983; 96:195–199. 23. Char DH. Thyroid Eye Disease. Boston: Butterworth–Heinemann, 1997:189. 24. Rush S, Winterkorn JM, Zak R. Objective evaluation of improvement in optic neuropathy following radiation therapy for thyroid eye disease. Int J Radiat Oncol Biol Phys 2000; 47: 191–194. 25. Garrity JA, Fatourechi V, Bergstralh MS, Brantley GB, Beatty CW, DeSanto LW, Gorman CA. Results of transantral orbital decompression in 428 patients with severe Graves’ ophthalmopathy. Am J Ophthalmol 1993; 116:533–547. 26. Carter KD, Frueh BR, Hessburg TP, Musch DC. Long-term efficacy of orbital decompression for compressive optic neuropathy of Graves’ eye disease. Ophthalmology 1991; 98:1435– 1442. 27. McCord CD. Current trends in orbital decompression. Ophthalmology 1985; 92:21–33. 28. Leone CR, Bajandas FJ. Inferior orbital decompression for dysthyroid optic neuropathy. Ophthalmology 1981; 88:525–532. 29. Hutchison BM, Kyle PM. Long-term visual outcome following orbital decompression for dysthyroid eye disease. Eye 1995; 9:578–581. 30. Char DH. Thyroid Eye Disease. Boston: Butterworth–Heinemann, 1997:233.

34 Medical Management of Thyroid Eye Disease GREGG S. GAYRE Atlantic Eye and Face Center, Cary, and University of North Carolina, Chapel Hill, North Carolina, U.S.A.

I.

INTRODUCTION

The ocular changes in thyroid eye disease (TED) range from mild to very severe and may include periorbital swelling, corneal exposure, eyelid retraction, diplopia, orbital congestion, and compressive optic neuropathy. Even if these changes are not sight-threatening, they can still cause significant ocular discomfort and disruption in vision. These changes are also perceived as disfiguring by almost all patients who experience them and may lead to social isolation. A wide array of surgical and nonsurgical treatment modalities is available in the management of TED, but the optimal treatment remains difficult. The majority of patients with TED will never require surgical intervention, and may have a greatly improved quality of life with careful medical management of their condition. II. EXAMINATION OF PATIENTS The medical management of patients with TED begins with frequent, thorough periodic examinations that screen for the presence of vision-threatening changes, and that manage the various ophthalmic manifestations that may interfere with visual function and contribute to ocular discomfort. A. History The ophthalmic examination should record any complaint of visual disturbance or ocular discomfort. Specifically, symptoms of double vision, decreased acuity, narrowed field of 335

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vision, or reduced color perception should be elicited. Patients are often keenly aware of the physical changes in their anatomy, describing a ‘‘wide eye,’’ ‘‘bulging,’’ or ‘‘staring’’ appearance to their globes. Often these patients are aware that their eyelids do not fully close, especially at night, or they may simply complain of excessive ocular surface irritation on awakening. Patients with increased orbital congestion may complain of periocular soft tissue swelling or increased orbital pressure that they dismiss as a nonspecific allergic reaction. Dry eye symptoms are common and may include foreign body sensation, itching, excessive mucus secretion, heaviness of the eyelids, sensitivity to light, pain, redness, burning, and blurred vision either with or without monocular diplopia. The patient should be questioned as to whether each of these perceived changes is experienced as stable or progressive. A careful review of both prescription and over-the-counter medications is essential and may reveal both topical and systemic drugs that should be avoided in patients suspected of having TED. Specifically, common medications that can exacerbate an already dry eye should be avoided. Examples of such medications include antiallergy sinus medications, blood pressure medications, antidepressants, diuretics, and topical vasoconstrictors such as Visine. If TED is suspected, but systemic disease has not been established, a careful review of the patient’s past medical history and a detailed review of systems are in order. Any history of thyroid gland dysfunction, pretibial edema, or phalangeal acropachy should be recorded. Symptoms suggesting systemic thyroid hormone dysfunction such as heart palpitations, weight change, mood disturbance, and temperature disturbance should be elicited. A review of the patient’s family history may reveal relatives with dysthyroid states or autoimmune diseases. A complete social history should include the use of tobacco products, as tobacco has been identified as a risk factor for a more severe course of ophthalmic disease. B.

Examination

The physical examination in patients suspected of having thyroid eye disease must include documentation of best-corrected visual acuity. The Snellen notation is the most common method of expressing visual acuity measurement and is measured monocularly, both at distance and near, after correcting for any errors in refraction. In addition to visual acuity disturbance, decreased color vision, disruption in the normal pupillary light reaction, and disturbances in the field of vision are indicative of optic nerve dysfunction seen in compressive optic neuropathy. Color vision disturbance may be detected by a relative desaturation in the color red in one eye as compared to the other. Color vision can be tested with pseudoisochromatic color plates. Patients with normal color vision can easily detect specific numbers and figures composed of and embedded in the dot patterns on these plates, but patients with impaired color vision may not detect these same symbols or numbers. Another test of color vision, the 15-hue test (Farnsworth-Munsell D-15 test), consists of 15 pastel-colored chips, which the patient must arrange in a related color sequence. The sequence is obvious to patients with normal color vision, but patients with color deficits may arrange these chips differently. Pupillary examination with documentation of the relative reaction of both pupils to light should be recorded. A relative afferent pupillary defect is detected with the so-called

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swinging flashlight test. Normally, the pupillary reaction to light should be equal in both eyes; with compressive optic neuropathy, the normal afferent pupil response in inhibited and the pupil’s response to light is impaired. Careful observation should be used to quantify the defect and evaluate it over time. Visual fields are also used to assess optic nerve function. Confrontational visual fields are important, but do not substitute for a formal assessment of peripheral vision using static automated perimetry (Humphry, Octopus) or kinetic perimetry testing (Goldmann or tangent screen). Perimetry is used to both confirm and quantify a visual field defect and then to follow its progression over time. Restrictive myopathy in TED is best detected by examination of the eyes in each of the six cardinal positions of gaze (right, up and right, down and right, left, up and left, down and left) as well as indirect up and downgaze. Forced duction testing may be used to confirm the restrictive nature of any existing ocular misalignment and the amount of strabismus can be measured with the use of prisms and then quantified in prism diopters. Examination of the periocular structures should include notation of any soft tissue inflammation, lagophthalmos, and lid lag in downgaze. Palpebral fissure heights and levator function should be noted. Superior and inferior scleral show, plus the distance of a light reflex to the upper and lower lid margin, should be documented. External photographs are extremely helpful for comparison to possible future changes. Exophthalmomometry using a Hertel exophthalmometer or similar device can be used to assess for proptosis. Although variations appear based on patients’ gender and race, a difference of more than 2 mm is considered abnormal. Slit-lamp examination should include assessment for dilated vessels over the insertion sites of the extraocular muscles and presence of chemosis, as either finding may be suggestive of increased orbital congestion. The presence of filaments over the superior bulbar conjunctiva and superior corneal limbus suggests superior limbic keratoconjunctivitis. Fluorescein and rose bengal dyes are useful to highlight any breakdown in the corneal epithelium and to assess tear breakup time. Assessment of the amount of aqueous tears produced in 5 min after the administration of topical anesthesia should be recorded. Such a test can establish basal tear production in the absence of stimulation by the corneal sensitivity reflex. Intraocular pressures (IOP) should be assessed in both downgaze and upgaze in order to rule-out artificial elevations of IOP caused by transient increased traction on the globe by a fibrotic inferior rectus muscle. True elevations in intraocular pressures should be managed with appropriate topical glaucomalytic agents. A dilated funduscopic examination is used to assess adequately the optic nerve head for increased cupping, pallor, or edema suggestive of optic nerve compression. Dilation will allow visualization of engorged retinal vessels suggesting orbital congestion, or the presence of chorioretinal folds suggesting orbital crowding. Radiographic or ultrasound studies may occasionally be necessary to assess for progressive crowding within the orbit or document impingement of the optic nerve. If active orbital inflammation is suspected, routine ophthalmic evaluation should be repeated every 3–6 months to assist the patient in the management of their symptoms and to rule out onset of vision threatening disease. Patients who demonstrate stable findings for 12–24 months can be reassured that their orbital disease has most likely stabilized. Annual examination is recommended for patients at risk for TED, but show no evidence of orbital involvement on initial examination.

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III. MEDICAL INTERVENTION Therapeutic medical intervention in TED has three goals: continuing localized ophthalmic protective measures against corneal epithelial breakdown, management of diplopia in patients with either active or stable TED, and anti-inflammatory treatment of acute orbital inflammation and compressive optic neuropathy. A.

Dry Eye Syndrome

Decreased aqueous tear levels that result in dry eye are common in GAO. A relative tear deficiency results from a combination of excess in tear evaporation due to widened palpebral fissues, inhibited blink response, and proptosis. Inflammatory infiltration of the lacrimal gland and/or accessory lacrimal glands might also contribute to a decrease in tears in TED. First, a person with dry eye should avoid anything that may cause dryness, such as an overly warm room, hair dryers, or the wind. Smoking is especially bothersome. Sunglasses and nocturnal taping of the eyes may be a helpful adjuvant to therapy. The next step in the treatment of decreased aqueous tear production is the addition of tear substitutes. Tear replacement by topical artificial tears remains the most widely used therapeutic modality in the treatment of dry-eye syndrome, and many cases, is the only treatment required. Artificial tears are available without a prescription. There are many brands on the market and each is slightly different. Patients may find one brand more effective than another. The exact frequency of administration of these medications varies: once or twice a day or as often as several times an hour. Most commercially available artificial tear preparations contain preservatives that may be toxic to the ocular surface, particularly with prolonged use. Such preparations should be avoided in any eye that requires use of drops more than four times daily to maintain comfort. A number of nonpreserved lubricating eye drops and ointments are commercially available. In many cases of moderate to severe dry eye, the frequent application of nonpreserved lubricating drops with bedtime application of lubricating ointment is sufficient. In severe cases of dry eye, especially if associated with very high levels of tear osmolarity or poor eyelid closure, it sometimes is necessary to use lubricating ointment or gels throughout the day, despite their potential for blurring of vision. Solid artificial tear inserts placed inside the lower lid on a daily basis gradually release lubricants and are available by prescription. These may be beneficial to patients unable or unwilling to apply topical artificial tears on a frequent basis. The retention of the aqueous tear film by punctal occlusion is also therapeutic for dry eyes. Punctal occlusion reduces tear film osmolarity, increases tear volume, and prolongs the residence time of externally applied tear substitutes. For patients who are using tear substitutes, punctal occlusion reduces the frequency of application required to obtain a desirable result. Punctal occlusion may be permanent or temporary. Temporary occlusion may be achieved by insertion of collagen implants into the canaliculi or silicone plugs into the punctal opening. Permanent occlusion can be accomplished with thermal or electrical cauterization of the puncta and canaliculi, by argon laser photocoagulation of the punctum, or by insertion of silicone plugs into the punctal opening. Silicone plugs are preferred because they may be easily removed if symptoms of ephiphora occur. The ability of high ambient humidity to retard evaporation and thereby preserve tear volume and reduce osmolarity can be achieved with the use of room humidifiers or

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with moist chamber spectacles or goggles. The role of a moisture chamber is to minimize significantly the airflow over the ocular surface by use of a transparent barrier that functions passively to prevent tear evaporation by creating a sealed chamber around the patient’s eyes. Prescription medications can occasionally be of help for dry eye syndrome. Vitamin A supplements, topical steroids, and topical cyclosporine 0.05–0.1% may be helpful in patients who have exhausted other forms of therapy. Oral cholinergic agonists such as Evoxac (cevimeline, Daiichi pharmaceuticals) 30 mg three times daily and Saligen (pilocarpine, MGI Pharma) 5 mg four times daily to stimulate tear secretion by the lacrimal gland have, in the experience of this author, recently proven to be an effective therapy for dry eyes in TED. In addition to dry eye management, the vast majority of patients experiencing active TED will require only palliative measures to increase comfort when active inflammation occurs. Assistance with smoking cessation is important, as tobacco use has been implicated as an exacerbating factor in TED. When periorbital edema secondary to TED occurs, it is important to reinforce practices that will minimize its fluid collection in the periocular tissue. Practical advice such as sleeping with the head propped up at least 30 degrees and applying ice packs daily to both eyes may be quite helpful in masking inflammatory signs. At least some studies also report that prescription diuretics may be effective in decreasing periorbital edema (1). This author has found that systemic nonsteroidal anti-inflammatory agents are effective in minimizing soft tissue swelling and decreasing subjective complaints of increased orbital pressure.

B.

Superior Limbic Keratoconjunctivitis

Superior limbic keratoconjunctivitis (SLK) is a chronic recurrent condition of ocular irritation and redness thought to result from mechanical trauma to the superior bulbar and tarsal conjunctiva. It has been shown to occur in association with Graves’ disease (2). SLK is characterized by the following features: inflammation of the superior tarsal conjunctiva in the form of a papillary conjunctivitis, inflammation of the superior bulbar conjunctiva, fine punctate staining with rose bengal and fluorescein of the cornea near the superior limbus, proliferation of superior limbic epithelial cells with micropannus formation, and filaments of the upper cornea and limbus. A stringy mucoid discharge is sometimes present and is associated with increase in severity of symptoms. Symptoms tend to vary in severity with time, with activity, and generally coincide with clinical signs. The disease is painful and the pain develops as the day progresses, usually reaching its maximum in a working individual in the late afternoon. It seldom interferes with sleep and is usually at its best on awakening. Discomfort is greatly increased by the presence of limbal or corneal filaments. These filaments are associated with intense foreign body sensation and blepharospasm that lead to a vicious circle of pain, spasm, increased conjunctival hyperemia, mucus secretion, and further filament formation. The classic treatment for SLK has been the local application of 0.5%–1% silver nitrate to the superior palpebral conjunctiva. This usually results in relief of symptoms for 4–6 weeks and may be repeated every 4–6 weeks without any untoward effects. The use of lubricants, topical vitamin A, n-acetylcysteine, pressure patching, bandage contact lenses, and botulinum toxin injections in the region of the superior orbital portion of the orbicularis muscle are reasonable options for treatment. Thermal cauterization and conjunctival resection have proved effective in patients with refractory disease (3,4,34–40).

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Eyelid Retraction

The use of topical and systemic sympatholytic agents is based on the belief that Mu¨ller’s muscle overaction, at least initially, plays a significant role in eyelid retraction seen in TED. Although an increased sympathetic tone in the hyperthyroid state has never been proven, some physicians have used topical sympatholytics and systemic beta blockers with varying reports of success in an attempt to control the early noninfiltrative manifestations of TED such as stare, lid lag, or lid retraction (5). In theory such agents would only be effective early in the course of the disease, before the fibrotic phase of lid retraction begins (6). Such sympatholytic agents would theoretically create a postganglionic Horner’s syndrome that, at least in theory, counteracts the lid retraction by producing mild ptosis. Guanethidine sulfate 5% eye drops, a topical alpha-adrenergic blocker administered three times daily, as well as similar agents such as bethandidine, and thymoxamine have been used (7,8). Time has shown that these agents have worked only temporarily, if at all, and are often irritating to the ocular surface. Other side effects include miosis, conjunctival injection, punctate keratitis, and discomfort on administration of the drop (9,10). Because of their limited effect and because the indication for use has never been approved by the Food and Drug Administration, this class of drugs is seldom used in the modern management of TED. More recently, local injection of botulinum A toxin has also been used as a nonsurgical means of treating TED-associated eyelid retraction. However, the temporary effect of this agent, and its potential side effects (significant ptosis and relative superior rectus palsy with diplopia), make botulinum A toxin a suboptimal mode of long-term correction of TED-associated eyelid malposition (11). D.

Diplopia

The nonsurgical management of double vision associated with TED ranges from the simple occlusion of the eye with greater restriction of motility to the more complex prescribing of prisms. Many patients are opposed to wearing an eye patch for occlusion. One simple alternative is to opacify one lens in a pair of spectacles using an opaque adhesive tape. A variation in this technique, termed sector occlusion, involves use of a piece of translucent adhesive paper applied to the posterior surface of a lens or lenses in order to obstruct vision in a particular direction, thus preserving binocular vision in nonrestricted fields of gaze (12). Prisms may be very useful in the treatment of certain patients who have a small degree of strabismus, but fitting of these prisms may be time-consuming and prone to trial and error. The amount of prism to give a patient for comfortable single binocular vision may be assumed arbitrarily to be one-third to one-half of the maximal phoria obtained on cover testing, or it may be titrated to the subjective response of the patient. Temporary ‘‘stick-on’’ prisms are particularly useful during active orbital inflammation and in the immediate postoperative period when frequent variability in the degree and nature of diplopia is common. Laying a series of small prisms adjacent to each other on a thin platform of plastic produces a so-called Fresnel prism. Fresnel developed these prisms in 1822 and Jampolsky and colleagues first described the use of paste-on membrane prisms made of flexible polyvinyl chloride in 1971 (13). Such prisms can be used as a permanent prescription or as a temporary measure when there is uncertainty as to the prism correction, especially when the strabismic condition is variable or when recovery is expected. These membrane prisms are obtained easily, relatively inexpensive, and are easy to adjust in strength. Their disadvantages are that they

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are somewhat dysesthetic, tend to yellow with age, and peel after about 3 months in place. Also, they do degrade acuity by about one line per every five-prism diopters. They are available in the ranges of 1–30 diopters, and may be confined to one lens, trimmed to fit a bifocal segment, distance correction, or part of the field of a lens, or prescribed in an oblique axis orientation for those patients who have both horizontal and vertical deviations. Once the degree of strabismus stabilizes, the prism power can be permanently ground into the patient’s spectacle, eliminating the impact on vision by the plastic prisms. Studies analyzing the success rate of prism therapy in TED are limited, but Flanders et al. report at least temporary relief of diplopia in 17 of 18 TED patients treated with Fresnel prisms (13). IV.

IMMUNOSUPPRESSION

As mentioned above, in the majority of patients with TED the ocular findings are selflimiting and can be relieved by local therapies. In approximately one-third of all patients with GAO, eye signs will become sufficiently disabling or disfiguring to warrant further treatment with systemic immunosuppression. The aim of immunosuppressive treatment is to avoid surgery altogether, or to decrease the activity of the inflammation in order to improve surgical outcomes (14). Before considering immunosuppression, it is useful to attempt to identify those patients most likely to respond. Up to 35% of patients with TED treated with systemic immunosuppression will show no significant response. The most likely explanation for this is that only patients with active orbital inflammation respond significantly to immunosuppressive treatment, whereas patients with manifestations of chronic fibrotic end-stage TED do not. Thus, an adequate assessment of disease activity might be important in determining a potential response to systemic immunosuppressive therapy (14). Several methods to identify active orbital inflammation and to assess for potential response to corticosteroids exist. Urinary GAG excretion levels, eye muscle echogenicity, orbital [111In] octreotide (octreoscan) uptake levels, relaxation times of extraocular muscles via magnetic resonance imaging, and somatostatin scintigraphy have been promising in assessing disease activity (14,22,31–33). A clinical activity score (CAS) based on four of the five classic signs of inflammation to assess for a potential response to systemic corticosteroids has been devised with a positive predictive value of 80%, and a negative predictive value 64% in potential steroid responders (23). The 10 items of the CAS are listed in Table 1 (23). Patients with four or more points (one point for each finding) have an increased likelihood of response to immunosuppression in TED. Systemic glucocorticoids are the most common immunosuppressants used in the treatment of TED and have been used with good success since the 1950s. Although the beneficial effects of corticosteroid use are clear, the precise mechanisms by which corticosteroids decrease the orbitopathy remains poorly understood. These agents probably serve in multiple capacities by suppressing immune function and decreasing inflammation, such as interference with the function of T and B lymphocytes; through reduction in the recruitment of neutrophils, monocytes, and macrophages; by inhibition of the function of immunocompetent cells; by inhibition of the release of mediators including cytokines; and, finally, by decreasing GAG synthesis and secretion by orbital fibroblasts (15,16). Any patient with evidence of compressive optic neuropathy should be considered for immediate steroid treatment. Relief of neuropathy is often obtainable and visual improvement is seen. However, relapse is common after discontinuation of corticosteroids

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Table 1 Clinical Activity Score Painful, oppressive feeling on or behind the globe, during the last 4 weeks Pain on attempted up, side, or down gaze during the last 4 weeks Redness of eyelids Diffuse redness of the conjunctiva, covering at least one quadrant Swelling of the eyelids Chemosis Swollen caruncle Increase of proptosis ⬎2 mm during 1–3 months Decrease of eye movements in any direction during 1–3 months Decrease of visual acuity of more than 1 line on the Snellen chart during 1–3 months The presence of four or more features is associated with an increased likelihood of response to immunosuppression therapy in TED.

and many patients may require additional treatment with either radiation or surgical orbital decompression to stabilize vision loss (17,18). Any patient with acute severe orbital inflammation and congestion should also be considered for steroid treatment. Such patients present with significant chemosis, injection, and periorbital edema, and a course of systemic corticosteroids in these patients will often result in a dramatic improvement in acute symptoms within a matter of days. Corticosteroids have a proven beneficial effect on soft tissue swelling, and impaired visual acuity, whereas a significant effect on proptosis and ocular motility is still debated (14). During active orbital inflammation, and particularly during the active phase of extraocular myositis, early suppression of orbital inflammation by systemic corticosteroids may limit damage to extraocular muscles and decrease both the degree of proptosis and the risk of protracted diplopia caused by postinflammatory intramuscular fibrosis (19). Finally, although it has been difficult to ascertain whether the treatment of an overactive thyroid gland affects the progression of the ophthalmic disease, some evidence suggests that eye findings worsen with at least one form of treatment of the hyperactive state: radioactive iodine therapy (15). Therefore any patient considered at high risk for worsening of TED during treatment with radioactive 131I should be offered systemic corticosteroids. Such high-risk features include smoking, high serum tetraiodothyronine concentration before treatment, high serum concentration of thyrotropin-receptor antibodies after treatment, and high serum concentrations of thyrotropin after treatment (15). Oral glucocorticoids, when administered at high dosages (60–100 mg/day) for several days, followed by a slow taper over the subsequent weeks, can be effective in up to two-thirds of patients requiring immunosuppression (20). The rate at which corticosteroid dosage can be tapered will depend somewhat on the clinical response, but decreasing the daily dosage by 5–10 mg per week usually is a safe guideline. Unfortunately, at least some patients will develop a recurrence of symptoms during or upon completion of the steroid taper and will require long-term steroid use to prevent exacerbation of symptoms. Whenever systemic corticosteroids are used, patients should be warned about the potential for adrenocortical insufficiency associated with steroid treatment. In the months following the withdrawal of long-term high-dose steroids, patients will require supplemental steroids in the event of trauma, surgery, or infection. Common side effects of corticosteroid use are listed in Table 2. Given these numerous side effects, it is preferable to limit the use of corticosteroids to a few months. Agents that protect against osteoporosis and

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Table 2 Common Side Effects of Systemic Glucocorticoid Use Acne Arthralgia Avascular necrosis of the hip Cataracts Cushingoid features Diabetes Fluid retention Glaucoma Headache Hirtsutism Hypertension Immunosuppression Increased bruising Increased appetite Irregular heartbeat Loss of libido Menstrual irregularities Mood disturbance Osteoporosis Paresthesias Poor wound healing Skin rash Stomach ulcers Weakness Weight gain

gastric irritation should be considered. Vitamin D (10,000 units once weekly) and calcium carbonate (0.5 gs orally, three times daily) may be helpful in protecting bones; agents that decrease stomach acid production may be useful in protecting the gastric lining. If extended treatment is required, immunosuppressive therapy or radiotherapy should be considered as adjuvant treatments that may allow a decrease in the dosage of systemic steroids. Local glucocorticoid therapy has been used in an attempt to avoid the systemic effects of steroids. Retrobulbar injection of steroids has been used occasionally in an attempt to treat locally the inflammation of TED while minimizing side effects. This treatment has not been proven to be as effective as systemic therapy in prospective studies and carries the added risk of injury to the globe (21). More recently, the use of intravenous methylprednisolone 1 g daily for 3 days followed by a rapid taper with prednisone has been advocated as an alternative form of corticosteroid treatment that may result in less morbidity. In the last 10 years, glucocorticoids have also been used intravenously, by the administration of methylprednisolone acetate (0.5–1.0 g) at different intervals. The cumulative dose of steroid ranges from 1 to 2 g in different studies (22). Although intravenous administration appears to have advantages over the oral administration in terms of effectiveness and possible side effects, this remains to be proven by randomized studies (22). In addition to corticosteroids, a number of other immunosuppressive agents have been proposed to treat TED in steroid-resistant or steroid-intolerant patients. These include

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cyclosporine, cyclophosphamide, azathioprine, and plasmapheresis (15). These agents are usually reserved for those rare patients whose disease fails to respond to or who cannot undergo standard treatment with corticosteroids, radiation, or surgery. The efficacy of some of these agents recently has come into question and the use of these medications has largely fallen out of favor (15). Other than steroid therapy, cyclosporine is the immunosuppressive drug that has been most thoroughly evaluated in the management of TED. This drug affects both humoral and cell-mediated immune reactions by inhibiting cytotoxic T-cell activation and antigen presentation by monocytes and macrophages, and by inducing activation of Tsuppressor cells and inhibiting production of cytokines (24). Several reports have evaluated the effectiveness of cyclosporine administration in TED (21,24–26). Although initial reports showed a dramatic improvement in ocular findings of TED, these positive effects were not uniformly confirmed in later studies (21). The use of cyclosporine has been reported in several studies, but only two were randomized and controlled (27,28). The first of these studies indicated a lower efficacy of cyclosporine than prednisone as a single-agent treatment. The second study confirmed this finding, but did find evidence to suggest that a combination of cyclosporine and prednisone may be more effective than either treatment alone (27). Thus, the use of cyclosporine might be indicated in association with glucocorticoids in patients who are resistant to steroids alone and in whom the persistent disease activity warrants continuing medical intervention. Side effects of cyclosporine are significant, however, and nephrotoxicity is one of the chief complications observed. Hypertension, hepatic toxicity, gastrointestinal distress, and paresthesias also may occur. Therefore, cautious levels of this drug (less than 7.5 mg/kg/ day) are recommended (27,28). Cyclophosphamide is an inactive cyclophosphamide ester of nitrogen mustard that is activated intracellularly by phosphamidase. Its biological activity resembles that of other polyfunctionally alkylating agents. It acts by selective depletion of activated B lymphocytes and inhibition of lymphocyte proliferation. Cyclophosphamide has been used for the treatment of TED since 1979 and its reported success rate is variable (29). No clinical trials have compared its efficacy to glucocorticoids. Cyclophosphamide 700 mg administered intravenously monthly for 1 year, or cyclophosphamide 85–150 mg/day in conjunction with corticosteroids, may help to decrease congestion and improve motility in some patients (29). However, because sterility occurs with administration of this medication, and its true efficacy is unclear, it should be reserved for patients whose disease has failed to respond to all other forms of therapy and who are no longer of child-bearing age. Other side effects of cyclophosphamide include leukopenia, alopecia, and hematuria. Azathioprine 2 mg/kg/day over 2–3 months has been advocated as an alternative and/or adjunctivant to corticosteroid therapy in TED. Controlled studies, however have found azathiaprine to be ineffective in TED (29,30). For a time, plasmapheriesis was used in the treatment of TED, but it has not been proved to be beneficial (22). The rationale for the use of plasmapheresis in the treatment of TED was based on the assumption that this procedure might remove either immunoglobulins or immune complexes possibly involved in the pathogenesis of the disease. Thus far, studies examining the efficacy of plasmapheresis have provided conflicting results: both favorable effects and treatment failures were reported. No study on the effects of plasmapheresis was randomized and controlled, and the interpretation of results is made more difficult by the frequent concomitant or subsequent treatment with steroids or immunosuppressive drugs (22).

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V. FUTURE TREATMENTS New treatments for TED are already being developed. As our understanding of the cause of TED grows, future treatments will be developed to disrupt the mechanisms responsible for active orbital inflammation. Treatment of patients at risk for TED will also be developed that can halt the inflammatory process before the disfiguring and potentially visionthreatening complications ever begin.

REFERENCES 1. Weetman AP, Wiersinga WM. Current management of thyroid-associated ophthalmopathy in Europe. Results of an international survey. Clin Endocrinol 1998; 48:21–28. 2. Kadrmas EF, Bartley GB. Superior limbic keratoconjunctivitis, a prognostic sign for severe Graves’ ophthalmopathy. Ophthalmology 1995; 102(10):1472–1475. 3. Wilson FM, Ostler HB. Superior limbic keratoconjunctivitis. Int Ophthalmol Clin 1986; 26(4): 99–112. 4. Mackie I. Management of SLK with botulinum toxin. Eye 1995; 9:143–144. 5. Gay AJ, Wolkstein MA. Topical guanethidine therapy for endocrine lid retraction. Arch Ophthalmol 1966; 76:364–367. 6. Charr DH. Thyroid eye disease. Br J Ophthalmol 1996; 80:922–926. 7. Buffam FV, Rootman J. Lid retraction—its diagnosis and treatment. Int Ophthalmol Clin 1978; 18:75–86. 8. Waldstein SS, West GH, Lee YY, et al. Guanethidine in hyperthyroidism. JAMA 1964; 189: 609–612. 9. Cartlidge NE, Crombie AL, Anderson J, Hall R. Critical study of 5% guanethidine in ocular manfestation of Graves’ disease. Br Med J 1969; 13:645–647. 10. Hodes, BL, Frazee L, Szmyd S. Thyroid orbitopathy: an update. Ophthalmic Surg 1979; 11: 25–33. 11. Biglan AW. Control of eyelid retraction associated with Graves’ disease with botulinum A toxin. Ophthalmic Surg 1994; 3:186–188. 12. Sarniguet-Badoche J. Early medical treatment of strabismus. In: Reinecke R, ed. Strabismus II. Orlando, FL: Grune and Stratton, 1984:83–89. 13. Flanders M, Sarkis N, Fresnel membrane prisms: clinical experience. Can J Ophthalmol 1999; 34:335–340. 14. Prummel MF, Wiersinga WM. Medical management of Graves’ ophthalmopathy. Thyroid 1995; 5:231–234. 15. Coday MP, Dallow RL, Managing Graves’ orbitopathy. Int Ophthalmol Clin 1998; 38:103– 115. 16. Bartalena L, Marcocci C, Bogazzi F, Bruno-Bossio G, Pinchera A. Glucocorticoid therapy of Graves’ ophthalmopathy. Exp Clin Endocrinol 1991; 97:320–328. 17. Day RM, Carroll FD. Corticosteroids in the treatment of optic nerve involvement associated with thyroid dysfunction. Trans Am Ophthalmol Soc 1967; 65:41–51. 18. Panzo GJ, Tomsak RL. A retrospective review of 26 cases of dysthyroid optic neuropathy. Am J Ophthalmol 1988; 197:75–84. 19. Gorman Ca, Waller RR, Dyer JA, eds. The Eye and Orbit in Thyroid Disease. New York: Raven Press, 1984. 20. Burrow GN, Mitchell MS, Howard RO, Morrow IB. Immunosuppressive therapy for the eye changes of Graves’ disease. J Clin Endocrinol Metab 1970; 31:307–311. 21. Bartalena L, Marcocci C, Pinchera A. Treating severe Graves’ ophthalmopathy. Baillieres Clin Endocrinol Metab 1997; 11:521–536.

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22. Bartalena L, Pinchera A, Marcocci C. Management of Graves’ ophthalmopathy: reality and perspectives. Endocr Rev 2000; 21(2):168–199. 23. Mourits M, Prummel MF, Wiersinga WM, Koornneef L. Clinical activity score as a guide in the management of patients with Graves’ ophthalmopathy. Clin Endocrinol 1997; 47:9–14. 24. Borel JF, Ryffel B, The mechanism of action of cyclosporin: continuing puzzle. In: Schindler R, ed. Cyclosporin in Autoimmune Disease. Berlin: Springer Verlag, 1985:25–32. 25. Editorial. Cyclosporine in autoimmune disease. Lancet 1985; 1:909–911. 26. Weetman AP, Ludgate M, Mills PVB, McGregor AM, Beck L, Lazarus JH, Hall R. Cyclosporine improves Grave’s ophthalmopathy. Lancet 1983; 3:486–489. 27. Kahaly G, Schrezenmeir J, Krause U, Schweikert B, Meuer S, Muller W. Cyclosporin and prednisone v. prednisone in treatment of graves ophthalmopathy: a controlled, randomized and prospective study. Eur J Clin Invest 1986; 16:415–422. 28. Prummel MF, Mourits MP, Berghout A, Krenning EP, Van der gaag R, Koornneef L, Wiersinga WM. Prednisone and cyclosporine in the treatment of severe Graves’ ophthalmopathy. N Engl J Med 1989; 321:1353–1359. 29. Kahaly G. Nonsteroid immunosuppressants in endocrine orbitopathy. Exp Clin Endocrinol 1991; 97:316–319. 30. Petros P, Weightman DR, Crobie AL, Kendall-Taylor P. Azathioprine in the treatment of thyroid associated ophthalmopathy. Acta Endocrinol 1990; 122(1):8–12. 31. Krenning EP, Kwekkeboom DJ, Bakker WH, Breeman WAP, Kooij PPM, et al. Somatostatin receptor scintigraphy with [111 IN-DPTA ⫽ D-Phel]- and [123I-Tyr3]-octreotide: the Rotterdam experience with more than 1000 patients. Eur J Nucl Med 1993; 20:716–731. 32. Kahaly G, Diz M, Han K, Beyer J, Bockisch A. Indium-111-pentreotide scintigraphy in Graves’ ophthalmopathy. J Nucl Med 1995; 36:550–554. 33. Krassas GE, Kaltsas T, Dumas A, Pontikides N, Tolis G. Lanreotide in the treatment of patients with thyroid eye disease. Eur J Endocrinol 1997; 136:416–422. 34. Ohashi Y, Watanabe H, et al. Vitamin A eye drops for superior limbic keratoconjunctivitis. Am J Ophthalmol 1988; 105:523–527. 35. Udell IJ, Kenyon KR, et al. Treatment of superior limbic keratoconjunctivitis by thermocauterization of the superior bulbar conjunctiva. Ophthalmology 1986; 93(2):162–166. 36. Mondino BJ, Zaidman GW, Salamon SW. Use of pressure patching and soft contact lenses in SLK. Arc Opthalmol 1981; 100:1932–1934. 37. Passion GA, Wood TO. Conjunctival resection for SLK. Ophthalmology 1984; 91(8):966– 968. 38. Grutzmacher, RD, Foster RS, Feiler, LS. Lodoxamide tromethamine treatment for SLK. Am J Ophthalmol 1995; 120(3):400–402. 39. Holland EJ, Olsen TW, et al. Topical cyclosporin A in the treatment of anterior segment inflammatory disease. Cornea 1993; 12(5):413–419. 40. Confino J, Brown SI. Treatment of SLK with topical cromolyn sodium. Ann Ophthalmol 1987; 19:129–131.

35 External Beam Radiotherapy for Thyroid Eye Disease CAROL A. HAHN and EDWARD C. HALPERIN Duke University Medical Center, Durham, North Carolina, U.S.A.

Fractionated external beam radiotherapy is a commonly used treatment for Graves’-associated orbital disease. The data supporting this therapy largely reside in single-institution retrospective reviews. The limited randomized prospective data present a mixed picture. With the understanding that this text is largely intended for nonradiotherapists, we will briefly review the mechanism of action of radiation therapy in Graves’-associated orbital disease, the manner in which therapeutic external beams of radiation are generated, the retrospective clinical data that can be mustered concerning this technique, and the available prospective data.

I.

PRESUMED MECHANISM OF ACTION OF EXTERNAL BEAM RADIATION

The term ‘‘radiation’’ refers to ‘‘the action or process of emitting rays.’’ The electromagnetic energy of ionizing radiation is propagated through space and may be thought of as packets of energy, called photons, and/or as waves with a specified energy, frequency, and wavelength. When an x-ray beam strikes living tissue, the photons strike electrons orbiting around the atomic nucleus. Because of the energy imparted to the electrons, they escape the attraction of the nucleus. Thus, we are left with an atom absent an electron. Since the electron has a negative charge, the remaining atom has a net positive charge. The creation of an atom that is missing an electron, and that has a positive charge, is called ionization. Ionizing radiation may create its biological effects either by directly striking the cell’s DNA and creating chemical changes or by interacting with chemical species else347

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Figure 1 Radiation-induced clonogenic cell death.

where in the cell that, ultimately, will affect the DNA. If ionizing radiation strikes the DNA and produces a biological effect it is referred to as the direct effect. If ionizing radiation strikes elsewhere in the cell and, subsequently, the effect is transmitted to the DNA by chemical intermediaries it is called the indirect effect. The vast majority of radiation’s effects on living tissue is via the indirect effect. Most living tissue consists of water. When ionizing radiation interacts with water it will transiently create ionized water species. These, in turn, will go through a series of rapid and complex radiochemical reactions that will result in the formation of chemical free radicals. A free radical is a chemical species with an electron in its outer atomic shell not paired with another electron with an opposite spin. Chemical free radicals are extremely reactive species and are the source of much mischief in biology. The more commonly produced free radicals from ionizing radiation are hydroxy free radicals (OH•). If the OH• is sufficiently long lived in the cell, it will interact with the purine and pyrimidine bases of DNA and bind to them. This will produce single- and double-strand breaks in DNA. If these breaks are irreparable by the cell’s repair enzymes, one of two pathways may be taken that lead to cell death. If the injury to the DNA is sufficient to prevent the cell from successfully carrying out replication, when the cell attempts to divide it will lose its homeostatic mechanisms, swell, burst, and die. This is referred to as clonogenic death (Fig. 1). An alternative pathway leading to cell death occurs when the cell’s monitoring processes detect serious DNA injury. If this injury is not repaired, then programmed cell suicide, called apoptosis, occurs that leads to DNA fragmentation and cell death (Fig. 2). The presumed mechanism of action of ionizing radiation in Graves’associated orbital disease is radiation-induced death of inflammatory cells, including lymphocytes, which inhibits the inflammatory attack on the periocular tissues and reduces pain and proptosis. The presumed reason for radiation’s failure to work successfully, in

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Figure 2 Apoptosis induced by radiation.

some cases, is that the inflammatory process is so longstanding, or so advanced, that fibrosis has occurred that cannot be reversed by killing acute inflammatory cells. II. GENERATION OF EXTERNAL BEAM RADIATION THERAPY FOR THYROID EYE DISEASE There are two commonly used types of machines for the generation of external beam radiation for the treatment of Graves’-associated orbital disease. A cobalt machine consists of a block of radioactive cobalt 60 housed in a lead box. The box has an aperture through which the radiation can escape. When the cobalt is moved to the ‘‘on’’ position it is pushed by a mechanical device over the aperture and a high-energy beam of radiation escapes. When it is pulled back into the ‘‘off ’’ position, it is removed from the aperture and the radiation is contained by the surrounding lead box. A high-energy linear accelerator, in contrast, consists of an electron gun that fires electrons down an accelerator tube. This tube imparts additional energy to the electrons. The electrons are slammed into a tungsten target. As they slow down in the target, energy is given off. This energy takes the form of a high-energy x-ray beam that may be shaped and modulated for the purpose of administering external beam radiation therapy. In modern medical practice, most treatment of Graves’-associated orbital disease is performed with a linear accelerator. III. RADIOTHERAPY TECHNIQUE When utilizing radiotherapy in the treatment of Graves’ disease, the target volume typically includes the entire content of the bony orbit in order to treat all of the tissues poten-

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tially involved with the inflammatory process. This delivers the entire prescribed dose of radiation to the optic nerve, retina, and posterior globe. Radiation tolerances of these structures, however, are well delineated and below the 2000 cGy typically utilized for treatment for Graves’ ophthalmopathy. The risk of retinopathy with therapeutic radiation is ⬍5% at 5000 cGy. The Stanford series of patients irradiated for Graves’ ophthalmopathy reported no retinopathy at 21 years (1). No specialized attempts are utilized for shielding of the posterior structures due to the very low expected and reported risks of complications. The lens of the eye, however, is quite sensitive to radiation. The minimum dose necessary to produce a cataract is approximately 200 cGy in a single exposure and larger doses are necessary with fractionated regimens. The latent period for cataract induction is dose related with latency of 4 years following receipt of 651–1150 cGy and 8 years for 250–650 cGy (2). Because the lens is the most radiosensitive structure in the treatment area, radiation techniques are designed to maximize coverage of the bony orbit, while minimizing lens dose. Field set ups are generally done with parallel opposed fields, treating from left and right sides to maximize dose homogeneity across the orbits bilaterally. Field borders are localized at the time of simulation and at this session the radiotherapy fields are set to include the target volume and exclude tissues not to be included in the treatment field. Inferior, superior, and posterior borders of the lateral fields are set by fluoroscopy about the bony confines of the orbit, following immobilization of the patient. Cerrobend, a lead

Figure 3 Half-beam block technique. Note divergence of posterior relative to anterior beam profile.


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Figure 4 Isodose plan: lines represent percentage dose received to enclosed volume.

alloy, is used to fabricate customized blocking to shield out the structures inferior and superior to the bony orbit such as the brain and sinus, which are not a target for the radiotherapy. The anterior field edge is typically set clinically at the lateral canthus, to place the beam edge posterior to the lens of the eye. This keeps the dose of radiotherapy to the ipsilateral lens quite low. Radiation beams, however, diverge. Thus, the field set behind the ipsilateral lens will diverge into the contralateral lens unless specialized techniques are utilized to avoid this. Two techniques are generally used to shield the lens: either angling fields back or utilizing half-beam blocking techniques. By angling back, the divergence is taken out of the beam in the direction of the lens by rotating the beam posteriorly, typically between 3 and 5 degrees. Alternatively, half-beam blocking techniques literally block out half of the radiotherapy field, so that the nondivergent center of the beam is located at the lateral canthus (Fig. 3). With this technique the amount of radiation reaching the lens is only that transmitted through the half beam block: about 3% of the dose (3) (Figs. 4, 5).

IV.

RETROSPECTIVE TRIAL RESULTS

The first reported use of radiotherapy for Graves’ ophthalmopathy was in 1936 by Henry Thomas, Jr., and Alan Woods. ‘‘X-ray treatment is being given to the orbits with the hope

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Figure 5 Dose volume histogram per lens: 100% of lens receives approximately 3% of prescribed dose.

of reducing swelling. While some improvement has been noted, it is still too soon to make any definite statement on the value of radiation in this patient’’ (4). Multiple reports have retrospectively analyzed the efficacy of radiotherapy for Graves’ ophthalmopathy. While these reports are useful in looking at responsiveness to therapy, the usual cautions involved in retrospective analyses apply. Patients are selected, and often less favorable patients are referred for radiation after failing alternative treatment regimens. The results are also further muddied by the concurrent utilization of steroids. Nevertheless, lessons are to be learned from retrospective analyses. Certainly these series provide the longest-term data on possible radiation complications. Peterson et al. reported on 311 patients treated at Stanford between 1968 and 1988 (1). Patients were organized into groups according to the era of treatment and the total radiation dose. Two groups, the pre-1979 and post-1983 patients, received 2000 cGy in 10 fractions of 200 cGy/fraction. Patients treated between 1979 and 1983 received 3000 cGy in 15 fractions of 200 cGy/fraction. Patients were reviewed 2–4 weeks postradiotherapy and thereafter as needed. Minimum follow up was 12 months. Signs and symptoms were scored with respect to five parameters: soft tissue, proptosis, eye muscle impairment,


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corneal involvement, and degree of sight loss. In response evaluation, 80% had soft tissue responses and 58% of these were complete responses. Over 75% of patients with corneal manifestations had a significant response with therapy. Abnormalities of extraocular muscle motility and proptosis also exhibited improvement: in 61% and 51%, respectively. A wide range of response to visual acuity defects was reported. Seventy-six percent of patients successfully discontinued steroid use following their radiotherapy, typically within several months of completing treatment. There was no outcome improvement in the patient group receiving higher doses. Acute side effects during treatment occurred in 10% of patients and consisted of self-limiting soft tissue inflammation. No long-term complications were observed. With follow-up to 21 years, no radiation-induced tumors have been detected. A second large series from France of 199 patients treated between 1977 and 1996 reported similar results (5). Twenty-six percent demonstrated good or excellent overall responses to therapy with 48% partial responses. The authors reported significantly improved results for patients treated with early or moderately advanced presentation and improved results for patients treated no later than 7 months after the beginning of ophthalmopathy. In follow up, four patients have required surgical treatment for bilateral cataract. No retinopathy or tumor induction have been reported with median follow up for 100 patients to 86 months. A number of smaller, retrospective series are available in the literature. A study by Palmer et al. of 29 patients indicated overall improvement in signs and symptoms in 48% (6). Soft tissue changes were most responsive and relieved in 78%, with proptosis reduced in 52%. Eye muscle motility, however, was only improved in 24%. Twenty-eight percent of these patients had previous orbital decompression that may have contributed to this result. A series by Marcocci et al. reported similar improvements in proptosis and ophthalmoplegia to those of the Stanford series, but systemic corticosteroids were utilized as a fundamental part of therapy (7). Although radiotherapy complications are generally rare, some studies have reported cataracts, retinopathy, and optic atrophy. Kinyoun et al. reported four cases of radiation retinopathy and optic atrophy after orbital irradiation (8). In retrospect, however, these cases were found to have major dosimetric errors delivering over 3500 cGy in ten 350 cGy fractions instead of 2000 cGy in 2 weeks (9). It is well recognized that larger fraction size is related to increased risk of late radiation complications. Some authors have suggested that diabetics may have an increased risk of retinopathy. Tumor induction by therapeutic radiation is a rare but serious complication. There is no known threshold, or safe dose, below which this complication is not believed to occur, but the probability is increased with higher doses. Snijders-Keilholz et al. have published a calculation of risk of tumor induction by orbital radiotherapy for Graves’ ophthalmopathy. They calculate a risk of 0.0064 (or 6:1000 persons) for fatal radiationinduced cancers or 1.2% (10). Since radiation-induced malignancies have a latency period of decades, for elderly persons the risk of orbital irradiation is minimal. The authors suggest, however, that treatment be reserved for older patients due to the theoretical increase in malignancy induction that the young may survive to realize. In summary, the retrospective literature supports the use of therapeutic radiation in treatment of Graves’ ophthalmopathy. The literature cautions us, however, as to the dangers of improper treatment and careful employment of radiotherapy to minimize risks of complications.

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EVALUATION OF PROSPECTIVE RANDOMIZED TRIALS

Prummel et al. from the University of Amsterdam conducted a randomized prospective, double-blind clinical trial to compare the value of prednisone to external beam radiation therapy (11). They enrolled patients, ages 20–70 years, who were euthyroid for at least 2 months, who had not received previous treatment for ophthalmopathy other than eye drops. The study was confined to individuals with moderately severe ophthalmopathy defined by moderate to marked soft tissue involvement, proptosis ⱖ23 mm, extraocular muscle involvement, and visual loss. Patients randomized to prednisone received 60 mg orally per day for 2 weeks, 40 mg orally per day for 2 weeks, 30 mg orally per day for 4 weeks, and, thereafter, the dosage was tapered by 2.5 mg per week in addition to sham radiation therapy. Patients randomized to receive external beam radiation therapy received 2 Gy per fraction, 1 fraction per day, for 10 fractions in 2 weeks plus placebo pills to mimic the prednisone. A response was defined by a decrease in signs or clinical symptoms from baseline values. Treatment failure was defined as an increase in symptoms. Twenty-eight patients were assigned to receive prednisone and sham radiation and 28 received radiotherapy and placebo. Therapeutic outcome after 24 weeks, as determined by change in signs or symptoms, was similar in each treatment group. Of the 28 patients who received prednisone, 14 responded (50%). Thirteen of the 28 patients receiving radiotherapy responded (46%); 36% in the radiotherapy group showed no change, as did 40% in the prednisone group. When each treatment group is considered as a whole, improvement was seen in total and subjective eye scores, which is attributable to improvement in the responders. There was no difference in degree of improvement between the two treatment groups, but the total eye score improved more rapidly in the prednisone-treated patients. Side effects seemed more marked in the patients treated with prednisone. Mean body weight in these patients increased from 71 kg to 73 kg at 24 weeks (p ⫽ 0.002). Hypertension, severe cirrhosis, hirsutism, behavioral change, and cushingoid face were more common in the prednisone-treated patients. The study suggested that the efficacy of external beam radiotherapy and of oral prednisone in initial treatment of patients with moderately severe Graves’ ophthalmopathy was similar but, because radiotherapy was better tolerated, it might be preferred. In contrast, a recent study by Mourits et al., also from the Netherlands, found the case for radiation therapy less persuasive (12). This study included patients with moderately severe Graves’ ophthalmopathy based on the presence of lid retraction, proptosis, impaired motility, an increase in intraocular pressure, along with enlarged extraocular muscles and increased intraorbital fat on a coronal computed tomogram (CT). A patient was judged to have moderately severe disease if he or she had, in their worse eye, motility impairment causing diplopia, proptosis ⱖ23 mm, moderate or severe eyelid swelling, or a combination of these. Patients included in this trial otherwise were similar to the prior randomized study: age 25–75 years, no treatment for orbital disease except drops, euthyroid for 3 months, and no patients with diabetes mellitus. All the patients received either 2 Gy per fraction of external beam radiotherapy in 10 fractions over 2 weeks or sham irradiation. Patients were examined 1 day before, and at 4, 12, and 24 weeks after radiation therapy. The definition of treatment outcome included major and minor criteria. Major criteria were improvement in diplopia grade and improvement in eye movements in any direction of ⬎8 degrees. Minor criteria were variations of 2 mm or more in lid aperture and


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reduction in eyelid swelling. The authors defined the response as ‘‘successful’’ if the patient improved in one or more major criteria or in the two minor criteria. Thirty patients were assigned to radiotherapy and 30 to placebo. All 30 patients assigned to radiotherapy completed the treatment. Of those assigned to placebo, 29 completed therapy. Treatment outcome was successful at week 18 in 60% of the irradiated patients and in 31% of the sham irradiated patients ( p ⫽ 0.04). Motility improved in 82% of the patients after radiotherapy and 20% after sham irradiation ( p ⫽ 0.004). Eyelid swelling was persistent in 36% of the irradiated patients and 42% of the sham irradiated patients ( p ⬎ 0.99). In more quantitative assessments there was no difference between the irradiated and sham-irradiated patients. The irradiated patients showed improvement in their clinical activity score more quickly than the nonirradiated patients. A significant number of patients in both arms of the study ultimately went on to undergo surgery. The mixed record of radiotherapy in this second randomized study lead the authors to conclude that, in patients with moderately severe Graves’ ophthalmopathy, radiotherapy should only be used for the treatment of motility impairment and not to ameliorate other signs or symptoms of the disease. Clearly, both studies suffer from a small patient population. If radiotherapy were beneficial, it would have to be considerably better than the alternative to be demonstrable in studies with only 28 to 30 patients in each arm. The solution to the uncertainty created by these studies might be resolved by a large-scale cooperative group trial, perhaps involving several countries, to generate sufficient patients to answer the questions posed.

VI.

CONCLUSION

The proposed mechanism of action of radiotherapy in the treatment of Graves’-associated orbital disease is killing of inflammatory cells and subsequent reduction in muscle swelling. Radiation beams are commonly generated by a linear accelerator. Therapy typically utilizes parallel opposed lateral photon beams to a dose of 20 Gy in 10 fractions over 2 weeks. Although retrospective studies generally support the value of external beam radiotherapy in selected patients, prospective studies offer a more mixed view. Further prospective trials are warranted to refine our understanding of the role of external beam radiotherapy.

REFERENCES 1. Peterson IA, Kriss JP, McDougall R, Donaldson SS. Prognostic factors in the radiotherapy of Graves’ ophthalmopathy. Int J Radiat Oncol Biol Phys 1990; 19:259–264. 2. Hall EJ. Radiobiology for the Radiologist. 4th ed., 1994. 3. Snow A. The use of independent collimation in the treatment of Graves’ ophthalmopathy. Br J Radiol 1999; 72:389–391. 4. Thomas HM, Woods AC. Progressive exophthalmos following thyroidectomy. Bull John Hopkins Hosp 1936; 59:99–113. 5. Beckendorf V, Maalouf T, George JL, Bey P, Leclere J, Luporsi E. Place of radiotherapy in the treatment of Graves’ orbitopathy. Int J Radiat Oncol Biol Phys 1999; 43:805–815. 6. Palmer D, Greenberg P, Cornell P, Parker RG. Radiation therapy for Graves’ ophthalmopathy: a retrospective analysis. Int J Radiat Oncol Biol Phys 1987; 13:1815–1820. 7. Marcocci C, et al. Orbital cobalt irradiation combined with retrobulbar or systemic corticosteroids for Graves’ ophthalmopathy: a comparative study. Clin Endocrinol 1987; 27:33–42.

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8. Kinyoun JL, Kalina RE, Brower SA, Mills RP, Johnson RH. Radiation retinopathy after orbital irradiation for Graves’ ophthalmopathy. Arch Ophthalmol 1984; 102:1473–1476. 9. Parker RG, Withers HR. Radiation retinopathy—letter to the editor. JAMA 1988; 259:43. 10. Snijders-Keilholz A, De Keizer RJ, Goslings BM, Van Dam EW, Jansen JT, Broerse JJ. Probable risk of tumour induction after retro-orbital irradiation for Graves’ ophthalmopathy. Radiother Oncol 1996; 38:69–71. 11. Prummel MF, Mourtis MP, Blank L, Berghout A, Koornneef L, Wiersinga WM. Randomized double-blind trial of prednisone versus radiotherapy in Graves’ ophthalmopathy. Lancet 1993; 342:949–954. 12. Mourits MP, van Kempen-Harteveld ML, Garcia MGB, Koppeschear HPF, Tick L, Terwee CB. Radiotherapy for Graves’ orbitopathy: randomized placebo-controlled study. Lancet 2000; 355:1505–1509.

36 Orbital Decompression: An Overview ROBERT A. GOLDBERG Jules Stein Eye Institute, UCLA School of Medicine, Los Angeles, California, U.S.A.

I.

INTRODUCTION

Orbital decompression surgery has changed a great deal from the days when it was performed primarily by neurosurgeons or otolaryngologists (1) and was a last option for patients with end-stage, severe thyroid-related orbitopathy. I believe it is appropriate to offer orbital decompression to patients with proptosis from thyroid related orbitopathy or non-Graves’ causes (2–5). Soft tissue repositioning over proptotic globes is esthetically and functionally suboptimal (Fig. 1). Traditional orbital decompression techniques that incorporate removal of the floor and medial wall are unbalanced, and have a rate of consecutive strabismus (as much as 30%) (6,7) that is unacceptable. I utilize a stepladder approach to orbital decompression that takes advantage of the lateral wall and intraconal orbital fat removal to minimize complications and maximize gradability, and allows me to more confidently approach orbital decompression in patients with small (but significant) amounts of proptosis. II. INDICATIONS FOR SURGERY The indications for orbital decompression have evolved substantially as a result of three processes. First, our understanding of the natural history of the disease and of the management of the disease in the inflammatory vs. noninflammatory phase has made surgery for optic neuropathy less common (8–10). Second, improved surgical techniques have allowed us to become more aggressive in cases of disfiguring proptosis. Third, our increasingly sophisticated patient population is less tolerant of the changes in appearance and comfort that characterize postinflammatory congestive Graves’ orbitopathy, and are more 357

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Figure 1 Patient with exophthalmos, who was treated with eyelid lengthening. Camouflage surgery, repositioning the eyelids over a prominent globe, is suboptimal from an esthetic and functional standpoint. ( 2001, Regents of the University of California.)

likely to request surgery. We now better appreciate the phenomena of compressive orbitopathy: diffuse pressure, pain, discomfort, and congestive edema that characterize the tight postinflammatory orbit and that respond well to decompression surgery (Fig. 2). III. PLANNING SURGERY: STAGING THE DISEASE The commencement of surgical rehabilitation is a major step in the life of a patient with Graves’ disease, and should be approached in a conservative and studied fashion. There is a long road ahead, and a good relationship with the physician and staff provides critical emotional support. There are rare severe risks of surgery and a likelihood of multiple stages of surgery, so informed consent should be thorough. It is best to consider surgery in the stable phase of the disease. Operating on an inflamed orbit is characterized by intraoperative bleeding and a rocky postoperative course. Furthermore, planning surgical rehabilitation requires assessing orbital, strabismus, and eyelid parameters that can be a moving target during the acute phase of the disease. It is possible that things will improve spontaneously to the point that less surgery or even no surgery would be required. A rule of thumb is to wait for 6 months of stable, postinflammatory disease before embarking on surgical rehabilitation (which begins with consideration for orbital decompression). There are, however, times when surgery is appropriately performed in the inflammatory stage of the disease. Although compressive optic neuropathy often responds to medical treatment in the inflammatory phase, there are cases in which persistent optic neuropathy (for example, in the range of 20/70 or worse) is unresponsive to aggressive steroid therapy or radiotherapy. If weeks have gone by, particularly if coexisting vascular disease is present, then surgical decompression of the nerve is appropriate and typically very effective. Also, some patients have a prolonged inflammatory course, or one characterized by exacerbations and remissions. They may be unable to work or function in daily life. Sometimes the best compromise is to accept the increased unpredictability of surgery, and

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Figure 2 Congestive orbitopathy. (A) Patient with late postinflammatory, congestive orbitopathy: periorbital edema and pain are related to congestion of venous outflow at the apex. (B) Following orbital decompression: edema and pain resolve. (C) Following eyelid repositioning surgery. ( 2001, Regents of the University of California.)

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to move forward with decompression even if the patient is not clearly in the postinflammatory phase. The decongestive effect of surgery often improves the soft tissue signs of the disease. IV.

BONY ANATOMY OF DECOMPRESSION

The most important characterization of orbital decompression has to do with the bony surface that is removed. In practical terms, four surfaces of the orbit are available for decompression (Fig. 2). The first surface is the medial wall overlying the ethmoid sinuses. The posterior medial wall overlies the apical portion of the muscles just anterior to the annulus of Zinn, and decompression in this area is often performed to treat compressive optic neuropathy. The second bony surface is the floor of the orbit, overlying the maxillary sinus. The third is the anterior lateral wall, which includes the zygoma surrounding the anterior tip of the inferior orbital fissure, which can be decompressed out to temporalis muscle and buccal

Figure 3 Diagram of areas of bone removed in various orbital decompression approaches. ( 2001, Regents of the University of California.)


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fat. The fourth is the deep lateral wall. This consists of the bulk of the greater wing of the sphenoid, which is comprised of thick bone in the area between the inferior and superior orbital fissure, and also the greater wing anterior to the tip of the superior orbital fissure including the fossa of the lacrimal gland. Decompression into this space is limited by the deepest portion of the temporalis muscle fascia and by the dura of the anterior and middle cranial fossa. Some authors have listed the orbital roof as a wall for decompression, but actually the roof itself consists only of thin bone bordering the frontal cranial fossa. Removal of this thin bone does not provide any significant volume expansion. The classic neurosurgical (11,12) approaches achieved their volume expansion by removing the deep superolateral areas of thick bone. With appropriate anatomical knowledge, this bone can be removed by the orbital surgeon extracranially through cosmetically hidden incisions. Traditional lateral orbital decompressions, in which the anterior segment of the lateral wall is removed to allow lateral soft tissue prolapse, offer limited volume expansion (13–16). A great deal of additional soft tissue expansion can be obtained not only laterally but also posteriorly by removing with a high-speed surgical drill the thick areas of bone in the deep portion of the sphenoid wing (Fig. 3). The sphenoid trigone forms a ‘‘door jam’’ that severely limits lateral expansion of the orbit. When it is removed back to the cortical bone overlying the middle cranial fossa and lateral to the anterior cranial fossa, the orbit obtains considerable lateral and posterior expansion (Fig. 4). Thinning of the greater wing of sphenoid directly posterior to the orbit may allow proptosis reduction in cases of ‘‘woody’’ orbits that have little ability to enlarge their shape laterally but may move as a unit directly posteriorly. Postoperative computed tomographic (CT) scans demonstrate this phenomenon (Fig. 5). Three areas of bone within the deep lateral orbit are available for removal in deep lateral orbital decompression surgery (17): the door jamb of the greater wing of the sphenoid, the lacrimal keyhole in the frontal and zygomatic bone, and the basin of the inferior orbital fissure within the lateral maxilla (Fig. 6). The average total bone volume available for removal from the combined three areas is 5.6 cc. Averages for the door jam, lacrimal keyhole, and basin are 2.9, 1.2, and 1.5 cc, respectively. The deep lateral orbital wall can

Figure 4 Transilluminated cadaver skull demonstrates areas of thick bone in the deep lateral orbit. ( 2001, Regents of the University of California.)

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Figure 5 Axial CT scan before (left) and after (right) deep lateral decompression. In this patient with a woody orbit (inset) the entire orbit moves directly posteriorly. ( 2001, Regents of the University of California.)

Figure 6 Areas of deep bone in the lateral orbit: doorjamb of the greater wing of sphenoid (red) and basin of the inferior orbital fissure (Green). ( 2001, Regents of the University of California.)


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Figure 7 Intraoperative photo shows coronal approach to orbital decompression with placement of rim onlay. Wide exposure of the medial and deep lateral orbit is achieved from an extraorbital approach. ( 2001, Regents of the University of California.) provide significant room for volume expansion, and I have observed that up to 6 mm of proptosis reduction can be obtained utilizing the lateral wall alone. V. INCISION DESIGN AND BONE SCULPTING Although I now use it only rarely for maximal bone removal, the widest exposure is obtained through a coronal approach (18,19) (Fig. 7). The coronal approach provides unimpeded access to the deep lateral orbit, which is superior to a direct lateral orbitotomy.

Figure 8 Eyelid crease incision. Wide exposure of the subperiosteal lateral orbit can be achieved by dissecting over the external zygoma (dotted area). ( 2001, Regents of the University of California.)

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Figure 9 (A) The lateral orbital rim is internally thinned in the area of the lacrimal keyhole, providing space for decompression and allowing better visualization of the superior orbital fissure. (B) A groove is burred from the lacrimal keyhole at the orbital rim, to the superior orbital fissure, identifying the diploic space within the greater wing of sphenoid. (C) After all the diploe is removed from the lesser and greater sphenoid wing, a T-shaped groove is present, including a large diploic lake adjacent to the inferior orbital fissure. (D) The basin of the inferior orbital fissure is removed out to the buccal fat and maxillary sinus mucosa. ( 2001, Regents of the University of California.)


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It leaves no visible scar (assuming an adequate hairline) and allows performance of a simultaneous upper facelift when desired. Through a coronal approach, the lateral rim can be left in place and thinned, augmented with specialized orbital rim onlay implants (3), or repositioned with osteosynthesis systems (16). After elevating the medial canthal tendon and lacrimal sac from their periosteal attachment, excellent exposure is obtained for medial and inferior orbital decompression. Most cases do not require maximal bone removal, and the eyelid crease incision is considerably less time-consuming than the coronal approach (Fig. 8) (20). The eyelid crease incision is well hidden cosmetically and offers excellent exposure to the three areas of thick bone in the lateral wall, as discussed above. Substantial bone in the deep lateral orbit is available for orbital expansion. The

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lateral orbital wall is now my first wall for decompression: by removing bone from each of the three areas of deep bone, combined with excision of 2–5 cc intraconal fat, 5 or even 6 mm of proptosis reduction can be achieved. Consecutive strabismus is substantially reduced. I have found the rate of the new-onset strabismus to be in the range of 5%, compared to 30% using medial or balanced medial and lateral decompression (21). The anatomy of deep lateral orbital decompression can be intimidating. This is the same bone that is removed through the classic neurosurgical approaches, and the surgeon must navigate around the dura of the anterior and middle cranial fossae. I have found that focusing on the river of diploe that runs through the sphenoid bone provides a reliable landmark that helps me to safely achieve maximal bone removal from the deep lateral orbit. The orbit is widely exposed in the subperiosteal plane. Periorbital dissection over the zygomatic prominence and superiorly over the frontal bone is necessary to achieve maximal deep orbital exposure. The orbit is entered subperiosteally and exposure is taken back to the superior orbital fissure, dividing the meningolacrimal vessel as necessary. Inferior dissection exposes the inferior orbital fissure which is opened in its anterior 1 cm as described by Jack Rootman, exposing the orbital floor. The first bone removed is the lacrimal keyhole, in the fossa of the lacrimal gland (Fig. 9). I remove a notch from the superolateral orbital rim both to achieve some proptosis reduction as the lacrimal gland prolapses outside the orbit, and also to help gain a better view of the superior orbital fissure. This dissection is performed with a side-cutting aggressive cutting burr. The orbital rim is left intact. I then make a groove in the direction of the superior orbital fissure. By aiming for the fissure, the surgeon naturally encounters the beginning of the diploic space within the greater wing of the sphenoid. Superiorly, this dissection is limited by the thin bone of the orbital roof. Particularly in a young patient, I have no hesitation to expose some of the frontal dura as I delineate the superior most edge of the thick bone of the deep lesser wing. The surgeon may switch to a 3 mm diamond burr for increased control as the deepest bone is removed. The diploic space within the greater wing is hollowed out using burrs and curettes. This leaves a ‘‘cliff ’’ of the orbital table of the diploe, which can be removed using the diamond burr, working back towards the superior orbital fissure. I then follow the diploe as it branches off inferiorly towards the inferior orbital fissure. Again, a combination of burrs and curettes can be used. The combination of the lesser and greater sphenoid wing diploic space forms the shape of the letter ‘‘T.’’ Above the inferior orbital fissure, the diploic space typically widens to form a large lake of diploe that can be hollowed out along the edge of the inferior orbital fissure, creating a large cavity. The diploe in the greater wing of the sphenoid also leaves a cliff of bone in the deepest part of the greater wing, and this can be removed using the diamond burr. Once the diploe has been removed, and the inner table and ‘‘cliff ’’ thinned, the remainder of the decompression is straightforward. The anterior lateral wall can be thinned over the temporalis muscle. I try to leave eggshell bone over the muscle, for fear that extensive removal of bone over the muscle may result in oscillopsia with chewing. No bone should be removed directly lateral to the globe. Lateral shift of the globe with increased pupillary distance may result. The basin of the inferior orbital fissure can be removed out to the buccal fat and maxillary sinus mucosa.


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The periosteum is then opened widely over all of the areas of bone removal, and intraconal fat can be accessed for graded removal as the assistant retracts the lateral rectus muscle superiorly using a curved malleable retractor. Pre- and postoperative CT scans demonstrate the significant orbital volume that can be achieved by removing the thick bone in the deep lateral orbit (Fig. 10). The risk of postoperative strabismus, based on my anecdotal experience, is lessened compared to medial approaches. With experience, the surgery can be performed in 45 min per side. Bone is removed directly behind the globe, allowing proptosis reduction even in ‘‘woody’’ orbits that have little ability to expand their shape horizontally. Bone is removed from the deep orbital apex, so I hypothesize that it should be as efficacious for treating compressive optic neuropathy as the medial approach. Removal of deep bone in the lateral orbit requires sculpting away layers of cortical and marrow bone in an anatomically complex area. It is possible to injure the globe or apical neurovascular structures, and it is also possible to enter the intracranial cavity and cause central nervous system (CNS) injury. Knowledge of anatomy and experience in the cadaver lab are prerequisites for safe surgery. Good illumination and retraction are paramount. It is not uncommon to create a small dural exposure, and cerebrospinal fluid (CSF) leaks can occur rarely. These are managed by packing the area of the leak with tissue grafts (with or without tissue glue) and by postoperative observation. The leak has no long-term egress route and is self-limited. A substantial dural tear or intracranial entry could cause bleeding or brain tissue injury. The surgeon should use utmost care to avoid extensive intracranial disruption, and neurosurgical backup should be available. In our series of over 100 deep lateral orbital decompressions, we have had 5 self-limited CSF leaks and no serious intracranial injury. VI.

REMOVAL OF INTRACONAL FAT

Intraconal orbital fat can be removed from either the eyelid crease or coronal incisions, and also through an inferior fornix conjunctival approach. A significant change in surgical philosophy and technique involves a new enthusiasm to remove intraconal orbital fat in cases characterized by enlargement of the fat compartment (as opposed to primary extraocular muscle enlargement). I shared many surgeons’ reluctance to enter the muscle cone and remove fat when I first read the reports in the plastic surgery literature (22). I first timidly and then more aggressively began removing orbital fat. To my surprise I have not noted complications related to removal of as many as 6 cc intraconal fat. Trokel and Kazim have published a large series reflecting the safety and efficacy of intraconal fat removal (23) and more recently reported successful treatment of compressive optic neuropathy (24). Removing 2–5 cc intraconal fat between the lateral rectus and inferior rectus, and if needed from the superiomedial and inferomedial compartments, provides additional proptosis reduction in patients with nonwoody, freely flowing fat. VII.

MEDIAL DECOMPRESSION

The lamina papyracea of the medial wall can be removed through an endonasal, coronal, or transcaruncular (Baylis) approach (25,26). The latter was first used by Henry Baylis in the late 1980s and further developed by Norman Shorr and myself. We have used it extensively for a multitude of medial orbital surgeries in the extraperiosteal and intraperio-

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steal spaces. The approach provides wide, rapid exposure of the entire medial wall from the roof to the floor through a cosmetically hidden incision, and is therefore ideal for medial orbital decompression (Fig. 11). For medial decompression, the lamina papyracea is removed from the sphenoid– ethmoid junction posteriorly to the equator of the globe anteriorly, and from the frontoethmoid suture superiorly to the maxilloethmoidal strut inferiorly. The roof of the ethmoid sinus (which is properly called the fovea ethmoidalis, not, as I often hear, the lamina cribrosa) adjoins the anterior cranial fossa. Severe intracranial complications can occur if it is breached, ranging from CSF leak, which is usually treatable by intranasal or rarely intracranial repair, to vascular injury to the anterior communicating artery, which can be

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Figure 10 Preoperative and postoperative CT scan (negatives, with right orbit outlined) demonstrate removal of thick bone in the deep lateral orbit. ( 2001, Regents of the University of California.)

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The transcaruncular (Baylis) incision provides wide, rapid access to the entire medial wall for medial and inferomedial decompression. ( 2001, Regents of the University of California.)

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Figure 11 Continued

fatal. It is not possible to avoid dural exposure or CSF leak in every case, but knowledge of the anatomy and study of preoperative CT scans to observe anatomical variations such as a sloped fovea ethmoidalis can minimize complications. As an alternative to the transorbital approach, the medial orbit can be decompressed transnasally. Most centers utilize the videoendoscope for visualization (27). There may be advantages in tight orbits, or if the surgical team is inexperienced in transorbital approaches, but the transcaruncular orbital approach provides equivalent exposure of the medial wall back to the optic canal ring, is rapid, and requires no special endoscopic equipment. When the floor is added as a third wall, it is best to preserve the maxilloethmoidal strut (27) to minimize postoperative dystopia (sunset syndrome) and strabismus (Fig. 12).


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Figure 12 By leaving intact the strut of bone between the maxillary and ethmoid sinuses, dystopia and strabismus can be minimized in inferomedial decompression. ( 2001, Regents of the University of California.)

VIII. ORBITAL RIM ONLAY GRAFT Another surgical option is use of the orbital rim onlay graft designed for me by Porex Corporation (College Park, GA) (Fig. 13) (3) and in which I have no financial interest. The rim onlay graft is placed in a subperiosteal plane through a coronal, canthoplasty, or eyelid crease incision. It advances the position of the inferolateral rim and lateral canthus, reducing the disparity between these support structures and the prominent globe (28). In cases that cannot be maximally decompressed because of patient desires or medical considerations, the rim onlay graft is a valuable technique to correct bony structural disproportions in the globe–eyelid relationship. It can be added to decompression, or used as an alternative. IX.

COMPLICATIONS

The most worrisome complications of orbital decompression are loss of vision or loss of life. Visual loss can occur intraoperatively, related to vascular or pressure damage to the optic nerve or globe, and postoperatively related to orbital hemorrhage or vasospastic ischemia. On our service we have had one patient lose vision the day after surgery, and I am aware of other cases of postoperative visual loss. Fortunately this is extremely rare. It is not completely preventable, but gentle surgical technique, good hemostasis, and rapid evaluation for evacuable hematoma if visual loss is recognized postoperatively, are appropriate. I do not use a postoperative drain and I do not believe there is any evidence that this can reduce the risk of visual loss. The primary risk of stroke or death is related to intracerebral complications. All of the cases of postdecompression stroke or death that I have reviewed relate to vascular injury of the anterior cerebral circulation. This occurs when instruments pass through the

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Figure 13 (A) Medpor orbital rim onlay graft designed to advance the lateral orbital rim. The implant should cover the rim. (B) Incorrect placement: the implant is too far outside the orbit and will not adequately advance the lateral canthus. (C, D) Patient with stable thyroid-related orbitopathy, before and after orbital rim onlay graft and eyelid repositioning surgery. No decompression was performed. ( 2001, Regents of the University of California.)


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orbital or ethmoid roof and damage the vessels that lie on the floor of the anterior cranial fossa. Early or late cerebral vasospasm results. The vasospasm can occur more than a week later, so patients who have had violation of the dura need to be monitored carefully for problems, perhaps with neurosurgical consultation. Fortunately most dural violations do not involve vascular or brain parenchymal injury, and a fatal outcome of the more common isolated CSF leak after orbital decompression is unlikely. CSF leak after medial decompression leads to CSF rhinorrhea, and there is a risk of meningitis or permanent fistula. If the leak is observed intraoperatively, it might be possible to patch the leak using free tissue plugs of fat or fascia, mucosal flaps, with or without tissue glue. The sinus should be firmly packed. If the leak is noted postoperatively because of persistent clear fluid nasal discharge that worsens with leaning forward and positive test for glucose (usually 2/3 of serum glucose), it is reasonable to observe for up to 1 week. The rate of spontaneous closure is high. However, a persistent leak with a nasosinus egress route will require additional surgical intervention, either with an attempt at identification and packing from below through the sinus, or by patching the leak from above via a craniotomy approach (29). I have managed half a dozen lateral CSF leaks after deep lateral orbital surgery. There is no egress route for the CSF and in all cases, after several days of a somewhat boggy orbit with CSF variably present at the wound, the leak has closed. This is no surprise to our neurosurgical colleagues, who of course routinely see some self-limited leakage after intradural procedures. Double vision is the most common significant complication of orbital decompression surgery. It is more common after unbalanced inferomedial decompression (30–32) and more likely in patients with type 2 disease (33). Patients must be informed of the risk of double vision and prepared for a second stage of eye muscle surgery, if needed. I prefer to wait 3 months after decompression before the second stage, because many cases of early strabismus will improve spontaneously. Numbness is common for the first 3 months after decompression, and mild permanent numbness is not rare because some small sensory branches are necessarily cut. The lacrimal, zygomaticotemporal, and zygomaticofacial senstory branches are at risk in lateral decompression. The infraorbital nerve is at risk from the inferolateral or inferomedial decompression. The inferior orbital nerve in particular is a large sensory trunk. If it is irreversibly damaged, symptomatic numbness of the cheek and upper lip will occur. Recurrent proptosis occurs both early, over the first 3 months, and late, after months or years. I have suspected that early recurrences relate to contraction of the periosteal vault, although I have not been able to prove this with imaging studies. Some early and all late recurrences relate to the instability of the underlying disease. Since these recurrences can be self-limited, it is generally best to take a conservative approach and allow 6 or more months to pass before considering additional orbital decompression. X. SECONDARY DECOMPRESSION Secondary (repeat) decompression presents some special challenges, but overall the effectiveness and safety is comparable to primary decompression. Orbital imaging studies, obviously, are paramount in surgical planning: evaluation of bony anatomy will suggest the most valuable source for additional bony expansion. In my experience there is frequently additional room in the deep lateral and deep medial orbit even after prior decompression. Of course, any virgin areas are logically approached first. If a previously operated

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Figure 14 Postoperative CT scan shows complete medial decompression. The ethmoid air cells have been removed back to the sphenoid–ethmoid junction (arrow). ( 2001, Regents of the University of California.)

area has to be approached, the surgeon should anticipate scar tissue. Fortunately in orbital decompression the surgical planes are bony, providing reliable guidance for re-exploration. XI.

RESULTS OF SURGERY

Various compilations of surgical results have been published. One must always interpret outcome studies of treatment of thyroid-related orbitopathy with the perspective of the natural history of the disease: the strong tendency for things to improve over time can be mistaken for treatment effect. Another variable is surgical technique. In my practice I frequently evaluate and obtain orbital imaging studies from patients who have had previous decompression surgery by different surgeons. I have noted a wide variation in bony removal. Sometimes even when the operative report suggests that the entire medial wall was removed, for example, the CT scan shows only removal of the anterior and middle ethmoid cells (Fig. 14). XII.

SUMMARY

Orbital decompression surgery is effective in reducing the pressure pain of congestive orbitopathy, improving the eyelid–globe relationship to restore corneal protection, and addressing disfiguring proptosis (Fig. 15). It is very effective in treating compressive optic neuropathy, but mild neuropathy can often be treated medically. Surgery for optic nerve compression is now performed only rarely in my practice, for patients whose condition


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Patient with postinflammatory thyroid-related orbitopathy and marked proptosis, before and after combined lateral and medial orbital decompression. ( 2001, Regents of the University of California.)

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fails to respond to medical therapy or who have congestive orbital pressure in the postinflammatory phase. There are significant complications, including rare severe ones, and patients must be well informed. The benefits are great and patients who have been through surgical rehabilitation for thyroid-related orbitopathy are some of my most grateful. Patients must be thoroughly informed, and accept the rare severe risks of surgery. I now use graded removal of the three areas of thick bone in the lateral wall as my first approach in cases without compressive optic neuropathy, adding intraconal fat removal in most cases. This represents a significant departure from the traditional approach that began with inferomedial decompression. However, inferomedial decompression, even with creation of a strut at the ethmoid maxillary junction, has a significant risk of consecutive diplopia and globe displacement. The sinuses are violated and chronic sinusitis can result, especially if the osteomeatal complex is compromised. The dura above the fovea ethmoidalis is not easily visualized, and laceration can result in intracranial bleeding or chronic CSF leak. By contrast, lateral decompression has less risk of inducing consecutive diplopia since the muscle cone is not shifted inferomedially. We have found that decompression only of the lateral wall has a rate of consecutive strabismus of approximately 5%, compared to a rate of 30% in medial decompression (29). If dural exposure is necessary for maximal decompression, this is accomplished under excellent visualization and the risk of CSF leak is minimized both by better exposure and by the lack of a potential external egress pathway. Up to 5 cc bony volume, and at least 6 mm of globe retrodisplacement, is available in lateral orbital decompression. Woody orbits with little ability to expand their shape or respond to fat excision can be decompressed by removing the deep lateral wall, allowing the orbit to move directly posteriorly. The lateral orbit can be approached through hidden incisions either through a coronal flap, which I use for cases in which maximal decompression is needed, or through an upper eyelid crease incision, which I find useful for the majority of cases in which I intend to move the globe back 3–5 mm. For patients with more proptosis than can be reduced through lateral wall decompression alone, the medial wall is added as a second wall, through a transcaruncular (Baylis) approach (or through the coronal approach if this has been chosen). Carrying this paradigm further, the floor (with preservation of the maxillary ethmoid strut) is now, for me, the third wall for decompression in cases that require maximal retrodisplacement. It is utilized only rarely, for maximal proptosis (more than 9 mm). When all the surfaces are combined, as much as 10 mm retrodisplacement can be obtained. The floor can be approached through the caruncular incision, through a separate fornix incision, through a coronal incision, or through a transantral or endoscopic nasal approach. The transantral and transnasal approaches do not allow easy sparing of the ethmoidal maxillary strut, and are now only rarely used in my practice for inferomedial decompression. REFERENCES 1. Ogura JH, Walsh TE. The trans-antral orbital decompression operation for progressive exophthalmos. Laryngoscope 1962; 72:1078–1097. 2. Goldberg RA, Hwang MM, Garbutt MV, Shorr N. Orbital decompression for non-Graves’ orbitopathy: a consideration of extended indications for decompression. Ophthal Plast Reconstr Surg 1995; 11:245–252. 3. Goldberg RA, Weinberg DA, Shorr N. Management of the patient with a relatively prominent eye: non-Graves’ orbital decompression and orbital rim onlay porous polyethylene implants. Facial Plast Surg Clin North Am 1998; 6:11–19.


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4. Goldberg RA. The evolving paradigm of orbital decompression. Arch Ophthalmol 1998; 166: 95–96. 5. Lyons CJ, Rootman J. Orbital decompression for disfiguring exophthalmos in thyroid orbitopathy. Ophthalmology 1994; 101:223–230. 6. Shorr N, Neuhaus RW, Baylis HI. Ocular motility problems after orbital decompression for dysthyroid ophthalmopathy. Ophthalmology 1982; 89:323–328. 7. Shorr N, Seiff SR. The four stages of surgical rehabilitation of the patient with dysthyroid ophthalmopathy. Ophthalmology 1986; 93(4):476–483. 8. Rootman J, Stewart B, Goldberg RA. Decompression for thyroid orbitopathy. In: Orbital Surgery: A Conceptual Approach, Philadelphia: Lippincott-Raven, 1995:353–384. 9. Neigel JM, Rootman J, Belkin RI, et al. Dysthyroid optic neuropathy. The crowded orbital apex syndrome. Ophthalmology 1988; 95:1515–1521. 10. Nunnery WR, Martin RT, Heinz GW, Gavin TJ. The association of cigarette smoking with clinical subtypes of ophthalmic Graves’ disease. Ophthal Plast Reconstr Surg 1993; 9: 77–82. 11. Kennerdell JS, Maroon JC. An orbital decompression for severe dysthyroid exophthalmos. Ophthalmology 1982; 89:467–472. 12. Naffziger HC. Exophthalmos: some surgical principles of surgical management from the neurosurgical aspect. Am J Surg 1948; 75:25–41. 13. Leone CR, Jr, Piest KL, Newman RJ. Medial and lateral wall decompression for thyroid ophthalmopathy. Am J Ophthalmol 1989; 108:160–166. 14. McCord CD Jr. Current trends in orbital decompression. Ophthalmology 1985; 92:21–33. 15. Wolfe SA, Hemmy D. How much does moving the lateral wall help in expanding the orbit? Ophthal Plast Reconstr Surg 1988; 4:111–114. 16. Thaller SR, Kawamoto HK. Surgical correction of exophthalmos secondary to Graves’ disease. Plast Reconstr Surg 1990; 86:411–418. 17. Goldberg RA, Kim AJ, Kerivan KM. The lacrimal keyhole, orbital door jamb and basin of the inferior orbital fissure. Three areas of deep bone in the lateral orbit. Arch Ophthalmol 1998; 116:1618–1624. 18. Mourits MP, Koornneef L, Wiersinga WM, et al. Orbital decompression for Graves’ ophthalmopathy by inferomedial, by inferomedial plus lateral, and by coronal approach. Ophthalmology 1990; 97:636–641. 19. Goldberg, RA, Weinberg DA, Shorr N, Wirta D. Maximal, three-wall, orbital decompression through a coronal approach. Ophthalmic Surg Lasers 1997; 28(10):832–843. 20. Antoszynk JH, Tucker N, Codere F. Orbital decompression for Graves disease: exposure through a modified blepharoplasty incision. Ophthal Surg 1992; 23:516–521. 21. Kennedy DW, Goodstein ML, Miller NR, Zinreich SJ. Endoscopic transnasal orbital decompression. Arch Otolaryngol Head Neck Surg 1990; 116:275–282. 22. Olveri N. Transpalpebral decompression of endocrine ophthalmopathy (Graves’ disease) by removal of intraorbital fat: experience with 147 operations over 5 years. Plast Reconstr Surg 1991; 87:627–641. 23. Trokel S, Kazim M, Moore S. Orbital fat removal. Decompression for Graves’ orbitopathy. Ophthalmology 1993; 100:674–682. 24. Kazim M, Trokel SL, Acaroglu G, Elliott A. Reversal of dysthyroid optic neuropathy following orbital fat decompression Br J Ophthalmol 2000, 84(6):600–605. 25. Shorr N, Baylis HI, Goldberg RA, Perry JD. Transcaruncular approach to the medial orbit and orbital apex. Ophthalmology 2000; 107(8):1459–1463. 26. Balch KC, Goldberg RA, Green JP, Shorr N. The transcaruncular approach to the medial orbit and ethmoid sinus. Facial Plast Surg Clin North Am 1998; 6:71–77. 27. Goldberg RA, Shorr N, Cohen MS. The medial orbital strut in the prevention of postdecompression dystopia in dysthyroid ophthalmopathy. Ophthal Plast Reconstr Surg 1992; 8:32–34.

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28. Goldberg RA, Relan A, Hoenig J. Relationship of the eye to the bony orbit, with clinical correlations. Aust NZ J Ophthalmol 1999; 27(6):398–403. 29. Wilson JL, Deschler DG, Kaplan MJ, Pilsbury HC. Complications of cranial base surgery. In: Weissler MC, Pillsbury HC, eds. Complications of Head and Neck Surgery. New York: Thieme, 1995:336–351. 30. Goldberg RA, Perry JD, Hortaleza V, Tong JT. Strabismus after balanced medial plus lateral wall versus lateral wall only orbital decompression for dysthyroid orbitopathy. Ophthal Plast Reconstr Surg. 2000; 16(4):271–277. 31. Hurwitz JJ, Birt D. An individualized approach to orbital decompression in Graves’ disease. Arch Ophthmol 1985; 103:660–665. 32. Garrity JA, Fatourechi V, Bergstralh EJ, et al. Results of transantral orbital decompression in 428 patients with severe Graves orbitopathy. Am J Ophthalmol 1993; 116:533–547. 33. Nunery WR, Nunery CW, Martin RT, Truong TV, Osborn DK. The risk of diplopia following orbital floor and medial wall decompression in subtypes of ophthalmic Graves’ disease. Ophthal Plast Reconstr Surg 1997; 13:153–160.

37 Fat-Only Decompression for Graves’ Orbital Disease BRIAN J. WILLOUGHBY and MICHAEL KAZIM Columbia University College of Physicians and Surgeons, New York, New York, U.S.A.

I.

INTRODUCTION

Graves’ orbitopathy features variable expansion of the soft tissue contents within the fixed bony orbital volume. During the acute phase of the disease, the extraocular muscles, lacrimal gland, and orbital fat become infiltrated with lymphocytes and are subject to volumetric expansion due to fibroblast deposition of glycosaminoglycans, fibrous tissue, and as yet unexplained expansion of the orbital fat compartment (1–3). The persistent increase in soft tissue volume results in the constellation of signs and symptoms associated with the chronic phase of Graves’ orbitopathy. Axial proptosis is often the most obvious feature to the patient. It can be the cause of significant cosmetic disfigurement and in turn give rise to lid position abnormalities and corneal exposure. It has also been postulated that ventral displacement of the globe places the recti muscles in a state of permanent tension, significantly contributing to reduced ocular motility (4). Compression of the orbital contents can produce a sensation of deep orbital pain and, in the extreme, cause optic neuropathy (5). The goal of decompressive surgery is to alleviate this set of signs and symptoms. Decompressive surgery produces its effects by increasing the ratio of orbital bony volume to orbital soft tissue volume. This has traditionally been achieved by removing one or more of the orbital walls. Although these surgical techniques have been developed to limit the associated complications, they still produce significant morbidity including globe ptosis, worsened strabismus, sensory defects, sinusitis, change in vocal quality, orbital cellulites, and loss of vision (6–9). The search for a decompressive surgical technique with a lower rate of associated morbidity has been aided by the advent of modern orbital imaging techniques. Careful 379

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analysis of computed tomographic (CT) or magnetic resonance (MR) imaging has identified the contribution of the enlarged orbital fat compartment to Graves’ orbitopathy. Peyster et al. showed that orbital fat accounted for 50% of orbital volume as measured by analysis in an unselected group of patients with Graves’ orbitopathy compared with 41.5% of that in normals (10). Patients can be classified into three groups by qualitative analysis of CT/MR imaging. The first group demonstrates normal extraocular muscles (EOMs) and proptosis due to expansion of the fat compartment. The second group on the other end of the spectrum shows markedly enlarged EOMs that fill virtually all of the intraorbital volume. The third and largest group features a balanced expansion of both the EOMs and orbital fat soft tissue volume. Careful image analysis and patient selection coupled with a technique for surgically debulking the orbital fat compartments has provided a safe and effective alternative method of orbital decompression. Orbital fat decompression provides an effective treatment for disfiguring stable-phase Graves’ proptosis and its accompanying signs and symptoms with an associated morbidity rate lower than that with bony decompression (11). II. PATIENT SELECTION Stable-phase orbital decompression, by definition, requires a patient in the postacute or inactive phase of thyroid orbitopathy, with sufficient time having passed (usually 6 months) for any spontaneous regression to occur. The patient should also be at least 6 months status-post any orbital radiation, following similar logic. The patient should be stable from an endocrinological standpoint and be medically cleared for approximately 2 h of surgery requiring general anesthesia. Candidates for orbital fat decompression are drawn from the same pool as those for bony decompression. Graves’ patients with disfiguring proptosis, corneal exposure unresponsive to medical therapy, and complaints of persistent deep orbital pain can poten-

Figure 1 Axial orbital computed tomographic scan in a patient with bilateral Graves’ orbitopathy shows marked axial proptosis and normal sized extraocular muscles. Expansion of the orbital fat compartment is presumably responsible for the proptosis.

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tially benefit from orbital fat decompression. Preoperative CT or MR imaging in the axial and coronal planes is helpful in determining those who will likely benefit the most from fat decompression alone. Those patients, for whom expansion of the orbital fat compartments contributes most significantly to the proptosis, are likely to have a more significant than average change post surgery. For those patients with predominantly enlarged rectus muscles the opposite is true (Fig. 1) (12). The average decompressive effect also varies with the preoperative Hertel measurements. For patients with preoperative Hertel measurements greater than 25 mm the reduction is the greatest. One should expect somewhat less effect in those patients whose preoperative measurements are less than 20 (11). III. PROCEDURE Orbital fat decompression may be accomplished through a variety of surgical approaches. The two most commonly utilized are the transconjunctival lower lid and upper lid crease incisions. As an alternative, the inferior orbital fat may be approached through a transcutaneous subcilliary incision. Orbital fat decompression is performed under general anesthesia. The patients receive intravenous antibiotics and corticosteriods intraoperatively. The patient also receives three doses of postoperative intravenous antibiotics. Corticosteriods may be continued for 5–7 days depending on the amount of swelling. Since the fat to be removed is from the intra and extraconal spaces, an appreciation for the location of the extraocular muscles must be maintained throughout the procedure. It may be of benefit when first performing the procedure to pass 4–0 silk traction sutures beneath the insertions of the muscles to locate them during deep dissection. There are three compartments from which intra and extraconal fat can be removed posterior to the equator of the globe. The largest volume of orbital fat is removed from the nasal and temporal quadrants of the inferior orbit. The supernasal quadrant yields a smaller volume of fat than the other two. It is approached through a lid crease incision when the superior nasal fat pad is clinically prominent, or when maximum proptosis reduction is desired. A transconjunctival approach is routinely taken to the lower eyelid. In patients with a lower lid tightly opposed to the globe, as is often the case in younger patients, a lateral cathotomy and inferior cantholysis may be performed to facilitate access to the inferior fornix and the lateral orbital compartment. Rake retractors are used to evert the lid margin and tarsal plate. The conjunctiva and lower lid retractors are incised approximately 5 mm below to the inferior boarder of the tarsal plate. A 4–0 silk suture is placed through the conjunctiva and lower eyelid retractors to reflect them superiorly and facilitate identification of the underlying orbital septum. The septum is opened with a unipolar needle-tipped cautery and the underlying fat pads are identified. The nasal fat pad is isolated first. Using primarily cotton-tip applicators, a blunt dissection method is used to define the anterior extent of the fat pad. While applying gentle anterior traction to the fat compartment with a large-toothed forceps, unipolar needle-tipped cautery on coagulation mode is used to dissect the fat sharply from the orbit by cutting the fibrous septations. Malleable retractors are placed into the wound to shield the lacrimal sac, eyelid, and globe. As the intermuscular septations and surrounding scar tissue are divided, the intraconal fat is advanced. The orbital fat in patients with Graves’ orbitopathy differs from that removed in cosmetic cases. In the former, fat is firmer, less slippery, and lends itself to removal en bloc. In fact, attempts to remove fat during decompression in a piecemeal fashion will limit the volume of fat that can be resected. Approximately 2–3 cc fat can be removed from this quadrant (Fig. 2).

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Figure 2 Intraoperative photo displays transconjunctival dissection of right inferiomedial fat compartment. The anterior fat and overlying orbital septum are grasped with a toothed forceps and advanced as the intermuscular septations and scar tissue are divided with the unipolar needle-tipped cautery. The anterior projections of the lower-lid fat compartments have been marked to facilitate identification.

The central fat pad is most often left undisturbed. The fat in this location is mostly anterior and only extraconal. Resection of this fat pad therefore has little effect on globe position. Only excessive amounts of prolapsing fat should be removed from this space. Overly aggressive resection in the central compartment will result in a hollowed out appearance of the lower lid contour. The inferior oblique muscle travels through this compartment and should be identified and protected. Lastly the inferotemporal quadrant is debulked. The largest volume of fat can be retrieved from this location. The anatomical boundaries for fat removal are the lateral orbital wall, the lateral rectus muscle superiorly, the inferior rectus muscle medially, and the globe supranasally. The intra and extraconal fat are removed as described above using malleable retractors to protect the lower lid and the globe. Approximately 3–4 cc fat can be taken from this quadrant. In each quadrant, as fat is dissected out with the unipolar cautery, care is taken to ensure hemostasis. Periodic irrigation with saline solution reduces heat built up from cauterization. In each quadrant we attempt to preserve Tenon’s capsule surrounding the rectus muscles. Resection of Tenon’s capsule with skeletonization of the muscle fibers is likely to contribute to perimuscular fibrosis and restrictive strabismus. When hemostasis is ensured, the conjunctiva is closed with two absorbable sutures. If a canthotomy and cantholysis was performed this is repaired. The superior orbit yields the greatest volume of fat in the nasal quadrant. The central fat pad can be trimmed of anterior fat to thin the lid; however, this may result in eyelid retraction due to fibrosis in the preaponeurotic plane. Removal of this fat has minimal effect on orbital volume. The lateral third of the upper lid is occupied by the lacrimal gland, behind which lies substantial posterior orbital fat. However, attempts to remove fat from the supratemporal orbit run the risk of damaging the gland or its neurovascular supply that pass through this compartment. The nasal fat pad is accessed through a lid


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Figure 3 Intraoperative photo shows dissection of the right superiomedial fat compartment through a medial lid crease incision. A malleable retractor protects the trochlea.

crease incision limited to the nasal third of the lid. A relaxing incision can be extended superonasally at a 45 degree angle to improve exposure. A 4–0 silk traction suture is placed at the lid margin. The orbital septum is opened with the adherent nasal fat pad with coagulation mode unipolar cavity. The deeper tissues are bluntly dissected with a cotton-tipped applicator. The trochlea, superior ophthalmic vein, and supratrochlear nerve occupy this quadrant. The trochlea should be palpated and a malleable retractor placed over it to avoid injury. The superior ophthalmic vein can often be atraumatically separated from the surrounding fat. All possible efforts should be made to preserve this vessel to limit postoperative orbital congestion. The terminal branches of the supratrochlear nerve are routinely sacrificed during this dissection. Sensation to the supranasal lid often returns within 6–9 months. Dissection of fat from this quadrant usually yields 2–3 cc fat. After hemostasis is ensured, the skin is closed (Fig. 3). Patients are admitted for postoperative observation for orbital hemorrhage, and ice packs are applied for the first 48 h after surgery. The skin sutures are removed at 5–7 days postoperatively. The full decompressive effect is generally appreciated by 3–4 months following surgery. IV.

RESULTS

In general, orbital fat decompression produces reduction of proptosis similar to that appreciated with bony decompression. Patients often appreciate improvement in deep orbital pain and lid retraction. Patients may also obtain a reduction in chemosis as well as an improvement in symptoms of surface irritation and, in some cases, an increase in ocular versions (Figs. 4, 5). An objective measure of the effectiveness of orbital fat decompression is most readily obtained by comparing pre- and postoperative Hertel measurements. When we examined these numbers on 81 patients decompressed with fat removal by Trokel and Kazim, we found the following results. Of 158 orbital fat decompressions performed, 112 (71%)

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Figure 4 Top. Preoperative photograph of a patient with bilateral Graves’ orbitopathy. Hertel measurements are 29/28 mm. Bottom. Appearance 6 months after bilateral orbital fat decompression performed through the upper eyelids. Hertel measurements are 26/23 mm. were decompressed with either a superior or inferior approach and 46 (29%) were decompressed through both; 17 required a second fat decompression to treat residual proptosis. In 15 orbits requiring a second surgery, the initial procedure had been limited to one lid. The remaining two orbits, which had already been decompressed through both lids, still achieved acceptable results through further fat-only decompression. Three additional orbits required bony decompressions as a second procedure to achieve the desired globe position. Patients who had an upper and lower lid orbital fat decompression had both a greater average and maximal reduction in proptosis (2.2 mm and 6.0 mm, respectively) than those patients decompressed through either the superior or inferior approach alone (average, 1.6 mm; maximum, 5.0 mm). Trokel and Kazim also found an important correlation between preoperative Hertel measurement and reduction in proptosis with orbital fat decompression. Patients with pre-


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Figure 5 Top. Preoperative photograph of a patient with bilateral Graves’ orbitopathy. Hertel measurements are 25/28 mm. Bottom. Appearance 6 months after bilateral superior and inferior orbital fat decompression. Hertel measurements are 22/23 mm.

operative Hertel measurements greater than 25 mm had an average reduction of 3.3 mm. Those patients beginning with a measurement less than 20.5 mm had an average reduction in proptosis of 1.0 mm. This trend persisted regardless of whether a one- or two-lid approach was used. Subjective outcome measures also substantiate the effectiveness of orbital fat decompression. Trokel and Kazim reported that all but the three aforementioned patients requiring subsequent bony decompression reported an improvement in both appearance and comfort following surgery. Pre- and postoperative photos of two patients are shown in Figures 4 and 5. Additional subjective improvement was noted in patient’s postoperative versions as well as improvement in 12 patients noted to have preoperative chemosis (11). Newer data from Kazim on an expanded number of cases (380 orbital fat decompressions) display an average reduction of proptosis of 4 mm for those patients with Hertel measurements of 25 mm or greater and an average reduction of 3 mm for those patients with a preoperative measurement less than 25 mm. These further results suggest a second

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important trend: the more cases performed, the more effective the technique (i.e., as the surgeon’s familiarity with the orbital fat space increases, so does the amount of resected fat) (12). Two other investigators, Olivari and Adenis, reported similar success in their publications on this subject. Olivari reported on his experience with fat decompression of 147 Graves’ orbits, finding a mean reduction in proptosis of 5.9 mm. He also found significant improvement in preoperative diplopia, tearing, foreign-body sensation, and complaints of retrobulbar pressure and headache (13). Adenis reported an average postoperative reduction of 4.7 mm in proptosis from his experience with 41 orbital fat decompressions. He also reported an improvement in preoperative oculomotor disorders and corneal exposure as well as a postoperative reduction in intraocular pressure for those patients with a preoperative intraocular pressure (IOP) of 21 mmHg and above (14).

V.

COMPLICATIONS

Possible complications of orbital fat decompression might include damage to the cornea or globe, postoperative lid malpositions, damage to the canalicular system, pupillary abnormalities from injury to the ciliary ganglion, direct injury to the optic nerve, postoperative hematoma with its associated sequelae, overcorrection, damage to the extraocular muscles, damage to the trochlea, infection, and various paresthesias from injury to sensory nerves exiting the orbit. In the hands of skilled surgeons familiar with orbital anatomy and experienced with this procedure, the intra- and postoperative complications have been limited. Orbital fat decompression is associated with fewer complications than bone decompression. In their early series Trokel and Kazim reported two cases of postoperative motility impairment from 158 fat-only orbital decompressions. They further relate that this was due to a transitory dysfunction of the inferior oblique. Both patients had complete resolution of symptoms within 3 months. They also reported that no patients suffered traumatic optic neuropathy, postoperative orbital hemorrhage, or developed a papillary abnormality (11). In his later series Kazim reported that of 380 fat decompressions, there were 5 cases of new or worsened diplopia, 3 of which resolved spontaneously and 2 required strabismus surgery. He also reported two patients who developed an Adies’ pupil following surgery. There were no other significant complications noted in this large series, nor were there any overcorrections (12). Olivari, from his series of 57 patients (108 orbits), reported 14 cases of temporary diplopia all resolving within 10 days. He also reported one patient who developed an orbital hematoma within 2 h of surgery and responded well to drainage, as well as 5 patients with persistent postoperative supraorbital nerve paresis (13). Adenis reported similarly low rates of complication: two cases of persistent postoperative diplopia, five cases of transient supraorbital nerve paresis, and two cases of upper eyelid malposition (14). Although the published rates of complications with orbital fat decompression are low, this should not suggest that this is a simple procedure. However, in the hands of a skilled surgeon familiar with the technique it can be a safe and effective method. One obtains familiarity and thereby avoids complications by starting with more limited fat resections and increasing the extent of the procedure as one’s skill and comfort with the procedure increases.


VI.

387

CONCLUSIONS

The evolution of orbital fat decompression has created a shift in the treatment paradigm of Graves’ orbitopathy. In properly selected patients this surgical technique can provide effective results with a low rate of surgical complications when compared to bony decompression, thereby providing an effective alternative as a primary modality for treatment of proptosis secondary to Graves’ orbitopathy. There are two keys to using this therapy in a successful manner. The first is patient selection. The patient who will benefit most from orbital fat decompression will have a proportionally larger expansion of the orbital fat compartment compared to the extraocular muscle volume expansion. Second is development of an adequate level of proficiency in an orbital space where most surgeons generally are not comfortable. This proficiency is developed over the course of performing fat reductions first on those patients requiring smaller resections and then progressing to larger and deeper dissections over time. This section also warrants discussion of some of the less well documented attributes of orbital fat decompression, either not previously discussed, or only briefly mentioned thus far. Multiple authors have noted postoperative improvement in extraocular motility following fat decompression. Olivari proposes this improvement to be related to a state of permanent stretch of all four rectus muscles in the proptotic Graves’ orbit. This condition, which is relieved with removal of intraconal fat, disrupts the normal length–tension relationship in the muscle and prevents adequate relaxation in the opposite field of gaze (13). An alternative explanation is that the process of fat removal lyses fibrotic intermuscular septations, permitting greater ocular rotation. Also provocative are reports of improvement in compressive optic neuropathy seen with orbital fat decompression. It has been proposed that compressive optic neuropathy results from direct pressure on the optic nerve by enlarged extraocular muscles and was a relative contraindication to orbital fat decompression. However, there are nine reports of orbits with dysthyroid optic neuropathy that improved in response to fat decompression (15,16). These cases suggest alternative mechanisms for Graves’-associated optic neuropathy. We believe that orbital fat removal can be used as the primary decompression procedure for correctly chosen patients, with a lower complication rate than associated with bony decompression procedures.

REFERENCES 1. Sisler HA, Jakobiec FA, Trokel SL. Ocular abnormalities and orbital changes of Graves’ disease. In: Tasman W, Jeager EA, eds. Duane’s Clinical Ophthalmology, rev. ed. Philadelphia: JB Lippincott, 1992: vol. 2, chap. 36. 2. Trokel SL, Jakobiec FA. Correlation of CT scanning and pathologic features of ophthalmic Graves’ disease. Ophthalmology 1981; 88:553–564. 3. Olivari N. Transpalpebral decompression of endocrine ophthalmopathy (Graves’ disease) by removal of intraorbital fat: experience with 147 operations over 5 years. Plast Reconstr Surg 1991; 8:627–641. 4. Olivari N. Transpalpebral decompression of endocrine ophthalmopathy (Graves’ disease) by removal of intraorbital fat: experience with 147 operations over 5 years. Plast Reconstr Surg 1991; 8:627–641. 5. Kazim M, Trokel S, Moore S. Treatment of acute Graves’ orbitopathy. Ophthalmology 1991; 98:1443–1448.

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6. Ogura JH, Thawley SE. Orbital decompression of exophthalmos. Otolaryngol Clin North Am 1980; 13(1):29–38. 7. McCord CD Jr, Moses JL. Exposure of the inferior orbit with fornix incision and lateral canthotomy. Ophthalm Surg 1979; 10(6):53–63. 8. McCord CD Jr. Current trends in orbital decompression. Ophthalmology 1982; 89:323–328. 9. Shorr N, Neuhaus R, Baylis HI. Ocular motility problems after orbital decompression for dysthyroid ophthalmopathy. Ophthalmology 1982; 89:323–328. 10. Peyster RG, Ginsberg F, Silber JH, Adler LP. Exophthalmos caused by excessive fat: CT volumetric analysis and differential diagnosis. Am J Roentgenol 1986; 146:459. 11. Trokel S, Kazim M, Moore S. Orbital fat removal. Ophthalmology 1993; 100:674–682. 12. Kazim M. Orbital decompression. Advanced techniques in orbital decompression and expansion. Presented at AAO meeting, New Orleans, LA, 1999. 13. Olivari N. Transpalpebral decompression of endocrine ophthalmopathy (Graves’ disease) by removal of intraorbital fat: Experience with 147 operations over 5 years. Plastic Reconstruct Surg 1991; 87:627–641. 14. Adenis JP, Robert PY, Lasudry JGH, Dalloul Z. Treatment of proptosis with fat removal orbital decompression in Graves’ ophthalmopathy. Eur J Ophthalmol 1998; 8:246–252. 15. Kazim M, Trokel S, Acaroglu G, Elliott A. Reversal of dysthyroid optic neuropathy following orbital fat decompression. Br J Ophthalmol 2000; 84:600–605. 16. Anderson RL, Tweeten JP, et al. Dysthyroid optic neuropathy without extraocular muscle involvement. Ophthalm Surg 1989; 20:568.

38 Practical Management of Strabismus and Diplopia in Thyroid Eye Disease NATALIE C. KERR University of Tennessee Health Science Center and St. Jude Children’s Research Hospital, Memphis, Tennessee, U.S.A.

I.

INTRODUCTION

Strabismus occurs in 15% of all patients with thyroid eye disease (1). Although most patients with thyroid eye disease and diplopia have a history of hyperthyroidism, they may be euthyroid, hyperthyroid, or hypothyroid at the time of presentation. Thyroid dysfunction has usually been present for 5 years before diplopia is manifest, with a range of 0–11 years for the appearance of diplopia after the onset of thyroid dysfunction (2). Thyroid eye disease usually presents with symptoms other than diplopia 2 years prior to the onset of diplopia. The average age of patients experiencing diplopia in thyroid eye disease is 50 years (2). Although women are more likely to be affected by a margin of 4 or 5:1 (3), older patients and men tend to have a more severe course of disease (4). Younger patients are less likely to develop strabismus with thyroid eye disease (5,6). Although not typical in thyroid eye disease, diplopia and strabismus can be the initial presentation. The ophthalmologist must be aware of other motility disorders that have similar presentations (Table 1). If there are signs of orbital inflammation, orbital pseudotumor and myositis must be considered in the differential diagnosis. Typically, there is no eyelid retraction and imaging studies show enlargement of the entire muscle complex, including Tenon’s capsule and tendons. Some systemic disorders, such as lymphoma, sarcoidosis, and amyloidosis, may present with unilateral restricted motility and proptosis. Biopsy of the involved muscle is often necessary to establish the diagnosis. Orbital cellulitis, which may be related to contiguous sinus disease, usually presents with unilateral 389

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Table 1 Differential Diagnosis of Acquired Restrictive Strabismus with Orbital Signs Orbital pseudotumor/myositis Lymphoma Sarcoidosis Amyloidosis Orbital cellulitis Mucocele Ruptured epidermoid cyst Metastatic neoplasm Rhabdomyosarcoma Lacrimal gland tumor Optic nerve glioma Carotid cavernous fistula Dural arteriovenous malformation

orbital inflammation and signs of acute infection. Epidermoid cyst, a congenital tumor, may rupture if not removed in childhood and cause an inflammatory orbitopathy. Metastatic neoplasms, particularly breast carcinoma and malignant melanoma, as well as rhabdomyosarcoma, lacrimal gland tumors, or gliomas of the optic nerve, may present with proptosis and limited motility. Imaging and/or biopsy may be required for clarification. Finally, acquired venous congestion from a carotid cavernous fistula or dural arteriovenous malformation may present with muscle enlargement, proptosis, chemosis, and motility disorders. Imaging, including angiography, will aid in definitive diagnosis. Extraocular muscle enlargement due to an immune-mediated process, as yet poorly understood, is the hallmark of thyroid eye disease and produces diplopia and strabismus in thyroid eye disease. During the early stages of thyroid eye disease, before restrictive strabismus is noted, microscopic examination of the extraocular muscles reveals infiltration between the extraocular muscle fibers with mononuclear inflammatory cells (7). Interfibrillar spaces are enlarged and contain an amorphous material that contains hyaluronic acid. Acute muscle enlargement may also be mediated by raised muscle tension secondary to transition from slow to fast muscle types induced by the hyperthyroid state (8). Following infiltration of the endomysial space of the muscle by lymphocytes, macrophages, and neutrophils, muscle cells decrease in numbers, and the contractile properties of the effected muscles may be compromised (7). At the cellular level, there is a marked expansion of the endomysial space in the extraocular muscles from biopsies of patients with recently inactive thyroid eye disease (9). Fibroblasts are stimulated in this process, and their productions of increased levels of glycosoaminoglycans (including hyaluronic acid) attract water osmotically, contributing to interstitial edema (10). In the healing phase of thyroid eye disease, the muscles become fibrotic and inelastic, resulting in restricted eye movement. During the acute, inflammatory phase of the disease process, many patients will undergo therapy with immunosuppression, radiotherapy, and/or orbital decompression. The reduction of inflammation may affect the development of diplopia and/or the response to surgical treatment. However, the role of these modalities in the prevention or treatment of motility impairment remains largely unknown. There may not be any effect on motility that can be attributed to these interventions (11). However, one study has shown that

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combined immunosuppression and radiotherapy reduces the need for subsequent decompression or strabismus surgery (12). Another study has found that following radiation, radiotherapy enlarged the field of binocular single vision in 11 of 17 patients who had ‘‘moderately severe’’ Graves’ orbitopathy (13). Nonetheless, 75% of these irradiated patients required strabismus surgery. Although existing diplopia and strabismus are often worsened following orbital decompression (14–17), a direct cause and effect relationship between surgical decompression and diplopia can not be made. The severity of the disease itself is the main determinant of whether or not diplopia will be present following the decompression (14,16,17). A common theme to many clinical studies of strabismus in thyroid eye disease is the variability noted from patient to patient with regard to presentation, orthoptic findings, and response to treatment. In this chapter, we will develop a practical approach to treating diplopia and strabismus in the patient with thyroid eye disease by recognizing common patterns of strabismus and how they respond to standard modes of surgical treatment. I will also discuss exceptions to the generalizations and theoretical explanations as to why certain phenomena are observed in this disease. By approaching the patient with a recognition of the common patterns of strabismus as well as the exceptions to common presentations, an individual treatment approach that responds to the specific issues causing visual disability and diplopia in the patient with thyroid eye disease can be developed. II. TYPICAL PATTERNS OF STRABISMUS The patterns of strabismus typically found in thyroid eye disease are hypotropia secondary to inferior rectus restriction, esotropia, hypertropia secondary to superior rectus restriction, hypertropia after recession of the inferior rectus, and A-pattern exotropia. The most common pattern of strabismus in thyroid eye disease is a vertical diplopia with upgaze limitation created by inferior rectus restriction (Fig. 1). One theory as to why

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Figure 1 (A) Right hypotropia in primary position. (B) Limitation of upgaze in right eye secondary to right inferior rectus restriction.

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this is the most common pattern of strabismus in thyroid eye disease is that there is a large area of contact between the inferior oblique and inferior rectus muscle, and inflammation in that area may result in large postinflammatory adhesions (1). Diplopia is most pronounced in upgaze. Large vertical deviations in primary gaze indicate an asymmetrical but bilateral restrictive process (Fig. 2). Small deviations in primary gaze indicate more of a symmetrical, but almost always bilateral, restriction of the inferior recti. With inferior rectus restriction, torsional diplopia is almost always present, although often masked by the large vertical deviation. Excyclotorsion is the rule, presumably because of inferior oblique overaction in an attempt to elevate the eye in the presence of a restricted inferior rectus (18). Superior rectus muscle weakness as a source of upgaze limitation has been suspected in Graves’ disease (19,20), but clinical experience dictates that superior rectus muscle palsy is unusual in Graves’ disease (21). In reality, upgaze dysfunction is secondary to the inelasticity of the opposing inferior rectus muscle (22). Medial rectus restriction results in an uncrossed diplopia and esotropia in primary gaze that increases on horizontal gaze (Fig. 3). If this is an asymmetrical process, the patient may have fusion with a compensatory head turn toward the more affected side. Esotropia, particularly in upgaze, can be accentuated by tight inferior recti, which are secondary adductors. Paresis of a lateral rectus muscle may rarely contribute to the esotropia and has been attributed to pressure on the sixth nerve in the posterior cone from enlargement of the muscles (23) or from direct trauma after orbital decompression (24). Superior rectus restriction has been reported to cause vertical diplopia, which is worse in downgaze. How frequently it occurs in thyroid eye disease remains unclear. In a large series (25), the superior rectus muscle was addressed surgically in only 12 of 117 muscles operated on to relieve diplopia in thyroid eye disease. However, downgaze restriction might also be caused by contractile dysfunction of an affected inferior rectus. This issue was brought up by Fells and colleagues in a 1994 article reviewing the histopa-

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Figure 2 (A) Exophthalmos in the right eye greater than in the left eye. (B) Limitation of upgaze in the right eye is greater than in the left eye.


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Figure 3 (A) Left esotropia in primary position. (B) Limitation of lateral left gaze secondary to left medial rectus restriction.

thology of muscle biopsies in Graves’ disease (7). However, clinical studies have not supported this observation (26). Inferior rectus paresis has only once been reported as a cause of hypertropia in downgaze and has been associated with superior oblique correction, not superior rectus overaction (27). Superior rectus restriction has often been blamed for late overcorrection of hypotropia in Graves’ ophthalmopathy after inferior rectus recession, which is another common pattern of strabismus in Graves’ disease (28). One series of 12 patients who had overcorrection of a hypotropia following inferior rectus recession were found to have increased proptosis and superior rectus muscle volume on the ipsilateral side when compared to a group that did not have overcorrection after inferior rectus recession (29), indicating that the contractured superior rectus was a causative factor. However, late overcorrections following inferior rectus recession might also be secondary to so-called unmasking of contracture of the contralateral inferior rectus. No predictive factors have been found for this postoperative overcorrection phenomenon (30). The variability of vertical strabismus in thyroid eye disease, even without surgery, may also share the blame. Frueh (31) reported two cases of spontaneous resolution of vertical diplopia. One case resolved 1 week after the initial visit, and the other case resolved 16 months after initial presentation. He postulated seven possible mechanisms to explain these observations. Compounding confusion regarding the causes of this problem is that late overcorrection can occur in other entities besides Graves’ disease (32) and that undercorrections may be as common as overcorrections (30). These issues await further study to clarify the underlying causes or factors causing late overcorrection of hypotropia following inferior rectus recession.

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The A-pattern exotropia seen in Graves’ disease may be particularly common following surgical decompression of the orbit. This is an important clinical finding because exotropia in downgaze may preclude binocular function when reading and/or create symptoms of a convergence insufficiency (Fig. 4). Other strabismic patterns encountered following surgical decompression of the globe include paresis of the inferior oblique muscles and the lateral recti. Inferior oblique paresis may be due to disinsertion of the inferior oblique muscles when the medial part of the orbital floor is removed (7). Also, reduced proptosis following decompression may encourage increased superior oblique action, further contributing to an A pattern. Ocular myasthenia occurs in the setting of Graves’ ophthalmopathy and can prove difficult to diagnose in the setting of a progressive restrictive strabismus. One expects a certain amount of change over time in the pattern of cicatricial progression with thyroid

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Figure 4 A-pattern esotropia (increased on upgaze and decreased on downgaze) following bilateral orbital decompressions.


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eye disease, but ocular myasthenia should be suspected if unexplained ptosis or shortterm variability of measurements is noted (7,33; Fig. 5). III. MEASURING STRABISMUS Ductions are key to understanding the pattern of muscle restriction producing diplopia in thyroid eye disease and in planning surgical treatment. If an eye does not look up, one can be fairly certain that there is a tight inferior rectus tethering the affected eye. The pattern and degree of restriction as noted on duction testing may be as important to the planning and outcome of strabismus surgery as the measurement of deviation in primary gaze (34). However, testing of vertical ductions in the presence of horizontal restriction and vice versa may be difficult to evaluate because ‘‘asymmetric limitation of horizontal movements may mask symmetric limitation of vertical movement’’ (35). Prism and alternate cover testing in primary and reading position, noting which eye is covered with the prism, is nonetheless essential for preoperative evaluation. Prism and alternate cover testing in other fields should be done when possible. If the patient cannot look directly at the fixation target in that field of gaze because of restricted motility, the prism and alternate cover test may not be accurate. If someone has such a restrictive strabismus that they cannot have a prism and alternate cover test performed in primary or reading position, one can neutralize the head position (instead of the strabismus) with a red filter and prisms to allow the patient to fuse in primary gaze (2). Maddox rod testing can be used to measure cyclotorsion, which is common in thyroid eye disease. Restriction of the superior recti will be associated with incyclotorsion, and restriction of the inferior recti will be associated with excyclotorsion (35). However,

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Figure 5 (A) Bilateral ptosis secondary to ocular myasthenia with lid swelling secondary to acute thyroid eye disease. (B) Right hypotropia secondary to thyroid eye disease with inferior rectus restriction and/or extraocular muscle weakness secondary to ocular myasthenia.

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cyclotorsion is not usually an important issue in surgical planning, as is discussed below in the section on surgical treatment. Binocular visual field assessment done at the Goldman perimeter may prove useful, especially in assessing the efficacy of surgery in expanding the binocular visual field (35). Hess charts assess the extent of binocular visual field as well as the pattern of restrictive strabismus (7). Forced ductions in the office to assess restrictive strabismus in thyroid eye disease can be hazardous. Patients who have thyroid eye disease often have thin conjunctivae, and large conjunctival tears can be produced trying to pull against severely restricted muscles. To verify a restrictive versus paretic motility problem in the office, intraocular pressure testing in various gazes may be utilized. It has been shown that intraocular pressure increases in fields of gaze where a restrictive eye muscle is playing a significant role in decreasing the motility of the eye. For instance, if the patient has a tight inferior rectus, a significant increase in intraocular pressure (greater than 10 mmHg) will be measured in upgaze (36–38). Under anesthesia, forced ductions are very useful for assessing the relative contribution of different extraocular muscles to restricted motility prior to the start of surgery.

IV.

CONSERVATIVE TREATMENT

It is important to offer patients conservative treatment for their incapacitating diplopia while you ask them to wait for stabilization of their motility disorder prior to definitive surgical correction. Occlusive treatment is often useful, especially if the patient already wears glasses and can wear a patch over the lens. Beware of tight patches over a proptosed eye with lid retraction. Abrasions can result. An occlusive contact lens is a cosmetically acceptable option to get rid of the diplopia. However, many patients are not contact lens candidates with Graves’ ophthalmopathy because of their exposure problems and preexisting corneal disease. Fresnel prisms are an attractive alternative, especially for large-angle vertical or horizontal deviations. They are easily interchanged as the strabismus evolves and can relieve diplopia in primary or downgaze until surgical intervention. The Fresnel prism will induce blurry vision in the affected eye. However, many patients are relieved to be rid of the diplopia and are willing to sacrifice a few lines of visual acuity for some limited binocular function. Few patients will actually tolerate ground in prisms over the long term because of the incomitant nature of their strabismus and/or large angle of deviation. In one series of patients with Graves’ disease and diplopia (25), only 8 of 45 patients could tolerate prisms as a long-term solution for their diplopia.

V.

CHEMODENERVATION

Chemodenervation has been used with variable success for the relief of diplopia in thyroid eye disease. While acute inflammation is a contraindication to surgical intervention (see Sec. VI), botulinum toxin A chemodenervation may be useful for relief of diplopia during the early stages of thyroid eye disease (39–43). Results are more impressive for relatively mild, acute dysthyroid strabismus than for long-standing, large-angle restrictive strabismus (42,43). In one series of 22 patients, all with acute disease, 46% had improvement after injection, and 32% required no further surgical treatment of their strabismus (43).


VI.

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SURGICAL INTERVENTION

The timing of surgical intervention for strabismus in thyroid eye disease is critical in achieving long-term relief of diplopia. The patient should be euthyroid. Hyperthyroidism may promote contracture of the extraocular muscles (8), while prolonged hypothyroidism after radioactive iodine is a risk factor for progression of orbital symptoms (44,45). Also, the patient’s eye must be in a noninflamed state when undergoing strabismus surgery. Otherwise, postoperative inflammation and scarring can prove disastrous (46,47). Most authors recommend waiting 3–12 months after orthoptic measurements have stabilized before attempting strabismus surgery (1,46,48,49). However, in some circumstances, debilitating strabismus may necessitate earlier surgery. As long as the patient’s eye is not actively inflamed, outcomes can be satisfactory (50). Even with a generous waiting period of 3–6 months, there is no guarantee of stability in strabismus. In one large series (25), 11 of 54 patients had changes after their surgery before which a 6-month waiting period for stability had been imposed. Strabismus surgery should never be undertaken if there is a possibility of needing orbital surgery. In a series by Nunery (15), patients who were already strabismic had a significant chance of experiencing further compromise of their motility following orbital decompression. Another series found progressive contracture and return of diplopia when orbital decompression was performed after strabismus surgery (51). Strabismus surgery in the diplopic patient who subsequently needed an orbital decompression would probably be of little to no benefit. Finally, strabismus surgery should always be completed before any lid surgery is done. At least 2 months of satisfactory results after the strabismus procedure is recommended before considering surgery for lid retraction. Choice of anesthesia for the surgical procedure is determined by the patient’s needs. In healthy patients who need bilateral procedures, particularly bilateral medial rectus recessions, general anesthesia is advantageous. It is convenient and comfortable for the patient to have their adjustable suture performed on the same day as the surgery. It is important to remember to use antiemetics, non-narcotic pain relief, and atropine or another vagolytic agent to prevent vagally mediated bradycardia or asystole and vomiting postoperatively. Local anesthesia is an attractive option if you only need to perform unilateral surgery, or if the patient has a significant anesthetic risk. Many patients requiring bilateral surgery who need local anesthesia can be approached with a staged procedure, and patients are very receptive to this. A subtenon’s block eliminates the risk of intraocular injection or inadvertent damage to an extraocular muscle encountered with a retrobulbar block. A generous lid block helps with exposure. An anesthesiologist to administer sedation during the procedure, particularly during the block, is essential for patient comfort. An inferior rectus recession on adjustable suture only takes 15–30 min to perform, so patients can usually be made quite comfortable during that short time under a local anesthetic. However, do not try to adjust on the same day that local anesthesia has been used, because the effects of the anesthetic may not have worn off by the afternoon following their surgery. Therefore, wait and adjust patients who have had local anesthesia on the following morning. Adjustable sutures are desirable when doing strabismus surgery in thyroid eye disease, although they are no panacea for preventing unwanted outcomes (23,52). There is a much greater need to adjust sutures in patients with Graves’ disease than with other adult diplopic patients. This is understandable in light of our inability to predict the elastic and contractile properties of the operated muscle, as well as the properties of all the other

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muscles of both eyes that may have been affected by the disease process and contribute to the diplopia. Some muscles are quite contractile when released from their insertion and may pull very tightly against the adjustable suture. Other muscles have no elastic or contractile properties after they are released from their insertion. A modified hangback adjustable suture or conventional scleral fixation has been advocated in this instance to prevent reattachment at the original insertion (1). Certain generalizations are helpful in producing excellent outcomes and avoiding disasters during strabismus surgery in thyroid eye disease (Table 2). The rationale for these generalizations comes from the following observations. First, doing as little surgery as possible is desirable because large A-pattern exotropias can result from large, bilateral inferior and medial rectus recessions (25). Although bilateral inferior rectus recessions have been advocated for correction of hypotropia and avoidance of late overcorrection of hypotropia (53), addressing the indifference in restriction between the two eyes and recessing only the more restricted muscle just enough to achieve orthotropia in primary gaze may be just as effective (25,34) and will avoid the complication of postoperative exotropia in downgaze. Second, free tenotomies will result in unpredictable and unwanted outcomes. Although putting a suture in a tight rectus muscle prior to disinserting it with scissors or a scalpel may be difficult (49), it is essential in controlling postoperative outcome. It is helpful to have an assistant hold a second muscle hook under the tendon a few millimeters back from the insertion to elevate the tight muscle off the sclera and allow for safe passage of the suture. Care must be taken, however, to avoid rupture of the muscle by excessive traction on the hooks. Third, resecting a muscle in the setting of restrictive strabismus must only be done when the antagonist muscle has been maximally recessed and there is no other way to relieve a residual deviation in primary gaze (Fig. 6). Resection in the setting of restrictive strabismus may worsen restriction of the globe. Finally, despite the presence of torsion and the A pattern, more problems may be created if surgical means are used to correct the pattern or the excyclotorsion (18). Correcting excyclotorsion will accentuate the A pattern, and vice versa. Since the cause of the problem is inferior rectus restriction, recession of this muscle will usually relieve the A pattern and the excyclotorsion simultaneously. The exception to this is a patient who will require supramaximal recessions of the inferior medial recti in both eyes. One-half tendon width medial displacements of the inferior recti may help avoid postoperative excyclotorsion (25). Following these guidelines and using adjustable sutures, excellent results can be expected. In the author’s experience, 90% of patients will achieve single binocular vision in primary and reading position without prism. Other studies report similarly good results (11,25). It is important to counsel your patients that you expect excellent results as you make them wait for their surgery. However, it may take more than one surgery, and I Table 2 General Principles for Surgical Correction of Strabismus in Thyroid Eye Disease Do as little surgery as possible to achieve single binocular vision in primary and reading positions. Never do a free tenotomy. Do not resect a muscle unless further recession of the antagonist muscle would result in significant loss of motility. Do not transpose a muscle. Do not operate on an A pattern or torsion.


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Figure 6 (A) Severe bilateral medial rectus restriction and inferior rectus restriction resulting in fixed globes bilaterally. (B) Satisfactory rehabilitation of large single binocular visual field after bilateral inferior and medial rectus recessions and left lateral resection.

always prepare my patients for another procedure when they give consent for the initial surgery. Reoperation rates vary from 17% to 50% (21,50). VII.

SURGICAL COMPLICATIONS

One complication to be avoided during strabismus surgery is asystole, either on the table during the procedure under anesthesia or during the adjustable procedure in the office. For this reason, request the anesthesiologist to give atropine or glycopyrrolate during the operative procedure, and leave an intravenous (IV) site in place while doing the adjustable. A vagolytic dose of atropine, a hypodermic, and a bag of IV fluid should be available should the patient have a syncopal episode associated with asystole or bradycardia during the adjustable procedure. Another problem encountered during or after the surgery is pain. Until the suture is adjusted, patients have a foreign body sensation caused by the large suture ends rubbing the surface of the eye. Position the long ends of the adjustable suture in the inferior cul-

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Figure 7 Upper and lower lid retraction after left superior and left inferior rectus recessions.

de-sac to keep them off the cornea and use copious amounts of ointment under the patch. Cover the knot of the adjustable suture with conjunctiva following the adjustment. Do not remove the knot until at least 10–14 days following the surgery, and, if possible, leave the knot in place until it dissolves on its own if it is covered with conjunctiva. The patient may experience significant bruising following a lid block. Also, if there is a significant amount of conjunctival elevation over the adjustable suture, it is not uncommon to see dellen formation. Thus, use topical steroids judiciously following the surgery, and warn patients to return to the clinic if they have a foreign body sensation that lasts more than 24 h. Corneal melting may result following thyroid eye muscle surgery, precipitated by pre-existing corneal compromise, exposure, elevated conjunctiva, and topical steroid use. Early diplopia in fields other than primary gaze is the rule immediately following strabismus surgery. Inelastic muscles and tissues have to stretch before a spread of comitance can occur. Reassure patients that diplopia in fields other than primary gaze will usually improve as time goes on (25). Diplopia more than 6 weeks following the surgical procedure can be caused by ‘‘late overcorrection’’ following inferior rectus recession to correct a hypotropia (see discussion in section on Typical Patterns of Strabismus). Convergence insufficiencies due to A-pattern exotropia can cause postoperative diplopia and can occur following large bimedial recessions coupled with large bilateral inferior rectus recessions. Avoiding large bilateral muscle surgery as much as possible, and doing only what is necessary to correct the patient’s diplopia in primary and downgaze will help prevent this problem. Convergence exercises may also be helpful. Finally, late diplopia can be the result of progressive disease. All patients must be informed prior to surgery that there is a high likelihood of needing further strabismus surgery to achieve single binocular vision in primary and downgaze. Lid effects can be impressive following strabismus surgery (Fig. 7). Inferior rectus recession in Graves’ disease result in an exacerbation of retraction of the lower lid (2,25,54), although lower lid retraction occurs even without muscle surgery (25). In patients without Graves’ disease, one can avoid lower lid retraction following recession of the inferior rectus by advancing the lid retractors after generous dissection of the capsulopalpebral head attachment to the inferior rectus. However, dissection of the lid retractors around the restricted inferior rectus in Graves’ disease is often impossible, and attempts at blunt and sharp dissection typically lead to opening of the orbital fat pad and secondary


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fat adherence syndrome. Therefore, reduce dissection around the inferior rectus. Also, recessing the contralateral inferior rectus may cause the upper lid on that side to droop because that eye is no longer experiencing a tonic drive for up gaze because of fixation duress (10). Finally, recessing a tight superior rectus will cause upper lid retraction (55). Therefore, warn patients that they will have changes in their lid position following strabismus surgery, and that they will likely need surgical repositioning of the lid once the strabismus is treated to achieve a cosmetically acceptable result. REFERENCES 1. Skov CM, Mazow ML. Managing strabismus in endocrine eye disease. Can J Ophthalmol 1984; 19:269–274. 2. Flanders M, Hastings M. Diagnosis and surgical management of strabismus associated with thyroid-related orbitopathy. J Pediatr Ophthalmol Strabismus 1997; 34:333–340. 3. Bartley GB, Fatourechi V, Kadrmas EF, Jacobsen SJ, Ilstrup DM, Garrity JA, Gorman CA. The incidence of Graves’ ophthalmology in Olmsted County, Minnesota. Am J Ophthalmol 1995; 120:511–517. 4. Kendler DL, Lippa J, Rootman J. The initial clinical characteristics of Graves’ orbitopathy vary with age and sex. Arch Ophthalmol 1993; 111:197–201. 5. Uretsky SH, Kennerdell JS, Gutai JP. Graves’ ophthalmopathy in childhood and adolescence. Arch Ophthalmol 1980; 98:1963–1964. 6. Metz HS, Woolf PD, Patton ML. Endocrine ophthalmomyopathy in adolescence. J Pediatr Ophthalmol Strabismus 1982; 19:58–60. 7. Fells P, Kousoulides L, Pappa A, Munro P, Lawson J. Extraocular muscle problems in thyroid eye disease. Eye 1994; 8:497–505. 8. Simonsz HJ, Kommerell G. Increased muscle tension and reduced elasticity of affected muscles in recent-onset Graves’ disease caused primarly by active muscle contraction. Doc Ophthalmol 1989; 72:215–224. 9. Pappa A, Jackson P, Stone J, Munro P, Fells P, Pennock C, Lightman S. An ultrastructural and systemic analysis of glycosaminoglycans in thyroid-associated ophthalmology. Eye 1998; 12:237–244. 10. Bahn RS, Heufelder AE. Pathogenesis of Graves’ ophthalmology. N Engl J Med 1993; 329: 1468–1475. 11. Mourits MP, Koorneef L, van Mourik-Noordenbos AM, van der Meulen-Schot HM, Prummel MF, Wiersinga WM, Berghout A. Extraocular muscle surgery for Graves’ ophthalmopathy: does prior treatment influence surgical outcome? Br J Ophthalmol 1990; 74:481–483. 12. Claridge KG, Ghabrial R, Davis G, Tomlinson M, Goodman S, Harrad RA, Potts MJ. Combined radiotherapy and medical immunosuppression in the management of thyroid eye disease. Eye 1997; 11:717–722. 13. Mourits MP, van Kempen-Harteveld ML, Garcıá MB, Koppeschaar HPF, Tick L, Terwee CB. Radiotherapy for Graves’ orbitopathy: randomised placebo-controlled study. Lancet 2000; 355:1505–1509. 14. Ruttum MS. Effect of prior orbital decompression on outcome of strabismus surgery in patients with thyroid ophthalmopathy. J AAPOS 2000; 4:102–105. 15. Nunery WR, Nunery CW, Martin RT, Truong TV, Osborn DR. The risk of diplopia following orbital floor and medial wall decompression in subtypes of ophthalmic Graves’ disease. Ophthal Plast Reconst Surg 1997; 13:153–160. 16. Paridaens D, Hans K, van Buitenen S, Mourits MP. The incidence of diplopia following coronal and translid orbital decompression in Graves’ orbitopathy. Eye 1998; 12:800–805. 17. Shorr N, Neuhaus RW, Baylis HI. Ocular motility problems after orbital decompression for dysthyroid ophthalmopathy. Ophthalmology 1982; 89:323–328.

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46. 47. 48. 49. 50. 51. 52. 53. 54. 55.

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with botulinum toxin. 26th Annual Meeting, The American Association for Pediatric Ophthalmology and Strabismus, San Diego, CA, April 12–16, 2000. Marcocci C, Bartalena L, Bogazzi F, Bruno-Bossio G, Pinchera A. Relationship between Graves’ ophthalmopathy and type of treatment of Graves’ hyperthyroidism. Thyroid 1992; 2: 171–178. Pequegnat EP, Mayberry WE, McConahey WN, Wyse EP. Large doses of radioiodide in Graves’ disease: effect on ophthalmopathy and long-acting thyroid stimulator. Mayo Clin Proc 1967; 42:802–811. Metz HS. Complications following surgery for thyroid ophthalmopathy. J Pediatr Ophthalmol Strabismus 1984; 21:220–222. Kramar P. Management of eye changes of Graves’ disease. Surv Ophthalmol 1974; 18:369– 382. Miller JE, Van Heuven W, Ward R. Surgical correction of hypotropias associated with thyroid dysfunction. Arch Ophthalmol 1965; 74:509–515. Long JC. Surgical management of tropias of thyroid exophthalmos. Arch Ophthalmol 1966; 75:634–638. Coats DK, Paysse EA, Plager DA, Wallace DK. Early strabismus surgery for thyroid ophthalmopathy. Ophthalmology 1999; 106:324–329. Sugar HS. Management of eye movement restriction (particularly vertical) in dysthyroid myopathy. Ann Ophthalmol 1979; 1305–1318. Ruttum MS. Adjustable versus non-adjustable sutures in recession of the inferior rectus muscle for thyroid ophthalmology. Binocular Vision Eye Muscle Q 1995; 10:105. Cruz OA, Davitt BV. Bilateral inferior rectus muscle recession for correction of hypotropia in dysthyroid ophthalmopathy. J AAPOS 1999; 3:157–159. Esser J, Eckstein A. Ocular muscle and eyelid surgery in thyroid-associated orbitopathy. Exp Clin Endocrinol Diabetes 1999; 107(S5);S214–S221. Hamed LM, Lessner AM. Fixation duress in the pathogenesis of upper eyelid retraction in thyroid orbitopathy. Ophthalmology 1994; 101:1608–1613.

39 Botulinum Toxin for Eyelid Retraction in Graves’ Disease MATTHEW D. GEARINGER University of Rochester, Rochester, New York, U.S.A. ALBERT W. BIGLAN University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, U.S.A.

I.

INTRODUCTION

Thyroid eye disease is one of the most common orbital disorders in adults, affecting women four times as often as men. Clinical manifestations include proptosis, restrictive myopathy, compressive optic neuropathy, and eyelid retraction. Patients with lid retraction may appear to have proptosis, or eyelid retraction can make proptosis more disfiguring. Likewise, patients with restriction of upgaze related to severe inferior rectus involvement and hypotropia may have the appearance of lid retraction or have true lid retraction on attempted upgaze. Careful observation and assessment are necessary to differentiate these three findings. Extreme degrees of eyelid retraction can cause exposure keratopathy and reduced visual acuity. This occurs through desiccation and abnormal tear distribution over the cornea, causing an optically irregular corneal surface. The extent and course of eyelid retraction should be included in the evaluation of patients with thyroid eye disease. II. PATHOPHYSIOLOGY Eyelid retraction in patients with thyroid eye disease is initially caused by increased secretion and sensitivity to catecholamines. Associated systemic findings include tachycardia, palpitations and sweating. Excess catecholamines cause activation of Mu¨ller’s muscle in the upper eyelid and the inferior tarsal muscle in the lower lid, both of which are sympathetically innervated smooth muscles. Prolonged contraction of these muscles, along with the concomitant inflammation in Graves’ disease, can lead to fibrosis of the eyelid retractors (including the levator palpebrae and capsulopalpebral fascia). 405

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The normal upper eyelid rests about 2 mm below the upper limbus and the lower eyelid lies at the lower limbus. Signs of eyelid retraction in thyroid eye disease include scleral show, widening of the palpebral fissure, and upper eyelid lag on downgaze. In addition to the cosmetic deformity caused by eyelid retraction, patients may suffer from exposure keratopathy. Symptoms may include dryness, burning, foreign body sensation, or blurred vision. Clinical signs may include conjunctival injection, punctate keratopathy, abnormal tear distribution, or corneal thinning in extreme cases. These clinical findings are secondary to increased tear evaporation from a larger ocular surface area, incomplete lid closure, mechanical abrasion during sleep, and possibly a decreased tear secretion from autoimmune lacrimal involvement. III. DIFFERENTIAL DIAGNOSIS Bartley (1) has recently reviewed causes of eyelid retraction and has characterized the causes as neurogenic, myogenic, and mechanistic. Neurogenic causes include contralateral ptosis, facial nerve palsy, aberrent innervation, and Parinaud’s syndrome. Myogenic causes include postoperative changes (either overcorrection of blepharoptosis or in association with recession of the vertical rectus muscles), Graves’ disease, or congenital myopathy. Mechanistic causes include proptosis from an orbital mass or shallow orbits (Crouzon, Pfeiffer, or Apert syndromes), cutaneous scarring, posttraumatic (accidental or surgical) scarring of lid structures, or irritation (from contact lenses, exposed sutures, or a high filtering bleb). IV.

TREATMENT

Lid-lowering procedures for thyroid eye disease may be performed for cosmetic reasons or to lessen exposure keratopathy. Surgical correction of eyelid retraction has traditionally, been deferred until orbital decompression and strabismus surgery has been performed or deemed unnecessary, as each of these may influence the position of the lids postoperatively. Surgical therapies for eyelid retraction (with or without Graves’ disease) can include gold weight implants, lateral tarsorrhaphy, or recession/detatchment of the upper or lower eyelid retractors. Biglan (2) has described the use of botulinum toxin for the temporary treatment of eyelid retraction in Graves’ disease. V.

INDICATIONS FOR BOTULINUM

Biglan (2) and Ozkan (3) have reported on the use of botulinum A neurotoxin for the temporary management of eyelid retraction in patients with thyroid eye disease. In Biglan’s initial series, the patients ranged from 39 to 63 years old. Each patient had satisfactory lid height following botulinum injection. The effect lasted from 3 to 6 months; thereafter the lids returned to the preinjection height. Several patients were reinjected, and all had a similar response to their initial dose. All the patients with exposure keratopathy had resolution of their clinical signs while the lids were in a normal position. VI.

PHARMACOLOGY

Botulinum A toxin (BOTOX, Allergan, Inc., Irvine CA) is a neurotoxin produced by Clostridium botulinum. It is thought to be the most potent naturally occurring toxin, with

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Figure 1 Diagram of the neuromuscular junction. Botulinum A toxin blocks the release of acetylcholine from synaptic vesicles into the synapse.

responses occurring at picomolar concentrations. Scott (4) was the first to use the toxin medicinally in humans, when he injected the recti muscles in an attempt to correct strabismus. Botulinum toxin acts by preventing release of acetylcholine from the presynaptic nerve terminals at the neuromuscular junction (Fig. 1). The toxin has a very high affinity for specific receptors on the presynaptic membrane. It is then endocytosed and gains access to the cytoplasm following a pH-dependent shift in protein configuration that exposes hydrophobic domains to the endosome membrane. In the cytoplasm, the toxin then blocks calcium-dependent release of acetylcholine, derailing neuromuscular conduction (5). This ‘‘chemodenervation’’ lasts 3–6 months. BOTOX is supplied in vials containing 100 units. Each unit is calculated by a bioassay based on the median lethal intraperitoneal dose in mice. The toxin is reconstituted slowly with the addition of nonpreserved normal saline; rapid addition of liquid or agitation can cause inactivation of the fragile protein molecule. Reconstituted solution is stored in a refrigerator and may be safely used for 24 h after reconstitution. VII.

METHOD

BOTOX is reconstituted with 2 mL nonpreserved normal saline, for a final concentration of 50 u/mL, or 5 U in 0.1 mL. The toxin is drawn into a tuberculin syringe using a large-bore 18 gauge needle, which is replaced with a 30 gauge needle. The upper eyelid is cleansed with an alcohol swab. The patient closes the eyes and the surgeon places a finger in the upper eyelid crease, gently depressing the globe to create a space between the globe and the orbital roof. The 30-gauge needle is placed just underneath the superior orbital rim and advanced along the roof of the orbit as if performing a frontal nerve block (Fig. 2). The botulinum toxin is then slowly injected into the space between the orbital roof and the levator palpebrae. There is no need for electromyographic control. If the

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Figure 2 Top. A 55-year-old man underwent a left orbital decompression to treat proptosis and lagophthalmos. A left hypotropia persists and there is moderate bilateral eyelid retraction. Middle. Five units of botulinum A toxin is administered into the levator palpebrae superioris muscle using a tuberculin syringe and a 30-gauge needle. Bottom. The same patient: reduction of eyelid retraction 2 weeks following treatment. needle is kept near the roof, direct injection into the superior rectus (and ensuing vertical diplopia) is unlikely because of the interposed levator. Suggested doses of 2.5, 5.0, or 7.5 U are recommended for mild (2 mm), moderate (4 mm), or severe (6 mm) lid retraction, respectively. VIII. RESULTS There may be some intrapatient variability of response. The eyelid will begin to drop after 12–24 h and reach its maximum response at 48 h (Fig. 3). There may be an initial, mild overcorrection (Fig. 4). The duration of the effect is between 3 and 4 months, at which


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Figure 3 Top. A 54-year-old woman had bilateral proptosis and mild eyelid retraction associated with thyroid orbitopathy. Bottom. The same patient 2 weeks after administration of five units of botulinum A toxin into the levator palpebrae superioris muscle.

time the lids begin to resume their initial position. At this time, retreatment with BOTOX can be considered. We normally see our patients 1 week after the injection. If there is an undercorrection at that time, reinjection is performed based on the eyelid position. IX.

COMPLICATIONS

Complications of the use of botulinum toxin injection for lid retraction in thyroid eye disease are expected to be similar to those following injection for strabismus; namely, ptosis, vertical diplopia, retrobulbar hemorrhage, and scleral perforation. Aside from a desirable transient ptosis, none of these complications occurred in the series reported by Biglan or Ozkan (2,3). If retrobulbar hemorrhage threatens to compromise optic nerve function, a lateral canthotomy can be performed to decompress the orbit. Application of gentle pressure to the closed lids after treatment will help to minimize this complication. If scleral perforation occurs, laser retinopexy or cryopexy should be performed. It is interesting to note that no changes in retinal structure were seen following intravitreal injection of botulinum toxin in rabbits (6). X. OTHER USES Botulinum has also been used with success to induce complete ptosis or chemical tarsorrhaphy in corneal conditions such as corneal melting, neurotrophic ulcers, or exposure secondary to facial nerve palsy. These patients can avoid tarsorrhaphy or repeated changing of bandage contact lenses. The usual dose of botulinum neurotoxin for these conditions

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Figure 4 Top. A 29-year-old woman had asymmetrical eyelid retraction. The right upper lid had previously undergone a Fasanella-Servat procedure for ptosis and had a normal lid height until the development of thyroid eye disease. Bottom. Following injection of 5 units of botulinum toxin there is a mild overcorrection, which resolved in 2 weeks.

is 10 U, slightly more than the usual dose to create a normal lid height in patients with Graves’ disease. The relatively smaller effect we see in patients with thyroid eye disease is likely due to the concomitant inflammation and fibrosis affecting their retractor complexes.

XI.

CONCLUSIONS

Botulinum A toxin is a useful adjunctive method to temporarily correct eyelid retraction in patients with thyroid eye disease, especially in patients with exposure keratopathy or cosmetic deformity who are awaiting orbital decompression or strabismus surgery. Considering the relatively high incidence of ptosis following botulinum injection for strabis-


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mus and blepharospasm, the levator seems be more susceptible to the toxin than the other extraocular muscles. The clinical response may vary depending on the duration of the lid retraction and extent of fibrosis of the levator structures. Patients with recent onset of eyelid retraction (and less fibrosis) may have a more accentuated response than patients with chronic eyelid retraction who may be undercorrected with a similar treatment dose. REFERENCES 1. Bartley GB. The differential diagnosis and classification of eyelid retraction. Ophthalmology 1996; 103:168–176. 2. Biglan AW. Control of eyelid retraction associated with Graves’ disease with botulinum A toxin. Ophthal Surg 1994; 25:186–188. 3. Ozkan SB, Can D, Soylev MF, Arsan AK, Duman S. Chemodenervation in treatment of upper eyelid retraction. Ophthalmologica 1997; 211:387–390. 4. Scott AB. Botulinum toxin injection of eye muscles to correct strabismus. Trans Am Ophthalmol Soc 1981; 79:734–770. 5. Coffield JA, Considine RV, Simpson LL: The site and mechanism of action of botulinum neurotoxin. In Jankovic J, Hallet M, eds. Therapy with Botulinum Toxin. New York: Marcel Dekker, 1994:3–10. 6. Hoffman RO, Archer SM, Zirkelbach SL, Helveston EM. The effect of intravitreal botulinum toxin on rabbit visual evoked potential. Ophthal Surg 1987; 18:118–119.

40 Surgical Management of Eyelid Retraction in Thyroid Eye Disease JONATHAN J. DUTTON Atlantic Eye and Face Center, Cary, and University of North Carolina, Chapel Hill, North Carolina, U.S.A.

In normal adults the upper eyelid margin generally rests 2–3 mm below the superior corneal limbus. The lower eyelid margin is usually at or 1 mm above the inferior corneal limbus. In these positions, the vertical interpalpebral fissure measures 8–10 mm. In the presence of eyelid retraction the vertical height of the palpebral fissure is generally wider than normal, and may be as much as 15–18 mm (Fig. 1). This is usually due to an abnormal elevation of the upper lid or a depression of the lower lid. However, even in the presence of significant retraction, the interpalpebral fissure can be within the normal range. For example, in Graves’ disease the lower lid may be retracted with a simultaneous ptosis of the upper eyelid. For this reason, when evaluating eyelid malpositions it is best to measure the eyelid marginal position with respect to the central pupillary reflex or corneal limbus.

I.

CAUSES

The causes of eyelid retraction are numerous. Primary retraction may be the first sign of an orbital tumor, with or without proptosis or extraocular muscle involvement. Trauma or orbital surgery may result in fibrosis of the levator muscle or orbital septum with consequent upper eyelid retraction. A pseudoretraction may be seen with marked proptosis, or associated with ptosis of the contralateral eyelid due to Hering’s law. Supranuclear retraction is seen most frequently from lesions near the posterior commissure in the dorsal mesencephalon. Intermittent retraction is associated with congenital nuclear or infranuclear conditions such as the Marcus-Gunn phenomenon. But the most common cause of eyelid retraction is thyroid eye disease. 413

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Figure 1 Graves’ disease with severe upper and lower eyelid retraction. II. MANIFESTATIONS The ophthalmic manifestations of Graves’ disease include chronic inflammation with ocular surface irritation, eyelid retraction, orbital congestion and proptosis, extraocular muscle restriction, corneal exposure, and compressive optic neuropathy. These findings are not strictly correlated with abnormal thyroid function, and most patients experience progressive ocular complications long after restoration of the euthyroid state. Early anatomical changes are related to osmotic edema from deposition of abnormal amounts of hyaluronic acid and inflammatory cellular infiltration. This results in increased orbital fat volume and thickened extraocular muscles, including the levator muscle. Such changes contribute to upper eyelid retraction. This inflammatory component is largely reversible with resolution of the disease, and in such cases the retraction may improve spontaneously. However, when chronic and longstanding, the inflammatory process may lead to fibrosis of the or-

Figure 2 Graves’ eyelid retraction shows the common pattern of lateral eyelid flare.

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bital fascial and suspensory systems, and permanent anatomical eyelid retraction. This deformity will remain even after abatement of the inflammatory manifestations. The major consequence of eyelid retraction is corneal exposure. This is exacerbated by the dry eyes that typically accompany this disease. Cosmetic deformity is also a significant issue for most Graves’ patients. Typically in Graves’ disease, the upper lid shows significant lateral flare as the high point of lid curvature is displaced laterally (1) (Fig. 2). This lateral flare presents a significant challenge in management of Graves’-associated eyelid retraction. III. MANAGEMENT The management of Graves’ eyelid retraction must be individualized according to the patient’s specific symptoms, and to the evolutionary stage of the disease. During the inflammatory phase, which generally lasts for 2–5 years, symptomatic therapy alone is indicated. This includes ocular lubrication, nocturnal patching, or a temporary lateral tarsorrhaphy for any corneal exposure. Botulinum toxin also has been shown to be useful in temporarily lowering the eyelid (2). It is preferable that any surgical intervention be delayed until the disease burns itself out, and the anatomical alterations have stabilized for at least 12 months. Although reactivation may be seen even several years after apparent stability, they are less likely after 1 year. While spontaneous improvement of retraction has been observed (3), this is rare. Surgical correction of fibrotic changes should be carefully staged for maximum benefit. If orbital decompression is necessary for relief of compressive neuropathy or for cosmetic reduction of severe proptosis, it must be performed as the initial procedure, since displacement of the globes will alter both ocular alignment and the eyelid positions. A period of 4–6 months is usually allowed for the globes to settle to their final positions before any further surgery. Strabismus surgery to correct any residual diplopia is the second stage in rehabilitation. This should precede eyelid retraction repair since excessive vertical rectus muscle recession or resection may further change eyelid positions. Recession of upper and lower eyelids, often combined with blepharoplasty, is the final step, and may be performed any time after strabismus repair. Retraction of the upper eyelid results from overaction and hypertrophy of the sympathetic Mu¨ller’s muscle (4,5), as well as from fibrosis of the levator muscle and its fascial sheaths of the levator aponeurosis (Fig. 3). In particular, contraction of the superior conjunctival fornix suspensory ligaments contribute to retraction through added traction on the posterior eyelid lamella. Correction should be aimed at all of these structures (6–8). Extirpation of Mu¨ller’s muscle alone will correct the eyelid retraction in about 30% of cases. In the remainder, some degree of recession of the levator aponeurosis will also be required to achieve a normal eyelid position. In practice, it is simpler, and the results better if both Mu¨ller’s muscle and the aponeurosis are recessed as a single unit. Scleral or cartilage spacers are not necessary, and in most cases result in a stiff and abnormally mobile upper eyelid. Residual lateral eyelid flare can be a significant problem, due primarily to contraction of superior forniceal ligaments. Various techniques to deal with this have been proposed (9), but dissection of these suspensory ligaments, as noted below, will generally provide good results. Lower eyelid retraction in Graves’ disease is caused by fibrotic shortening of the inferior rectus muscle and its capsulopalpebral attachments to Lockwood’s ligament. To some extent, hypertrophy of the inferior sympathetic muscle of Mu¨ller may also be contrib-

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Figure 3 Lateral cross-sectional anatomy of the upper eyelid. LA, levator aponeurosis with slips inserting onto the tarsal plate and orbicularis muscle; MM, Mu¨ller’s muscle inserting onto the tarsal plate.

utory. Correction requires disinsertion and recession of the retractors along with Mu¨ller’s muscles as a single unit. Because of gravitational effects on the lower eyelid, a scleral, fascial, or alloplastic spacer for support is necessary for recessions over 2–3 mm. Also, in the face of significant proptosis, the lower eyelid must be projected both upward and forward, which cannot be achieved without a graft. IV.

¨ LLER’S MUSCLE RECESSION LEVATOR APONEUROSIS AND MU

The indication for this procedure is eyelid retraction due to thyroid eye disease with chronic corneal exposure or cosmetic deformity. As mentioned above, it is desirable for the disease process to have been stable for at least 12 months to minimize the risk of recurrence. The eyelid incision is marked within the pre-existing or proposed upper eyelid crease, 8–10 mm above the eyelid margin. About 0.5–1.0 mL local anesthetic is infiltrated along the marked line. The skin is cut along the line with a scalpel blade to expose the orbicularis muscle. The skin edges are tented up with forceps and the orbicularis muscle is cut through with scissors to enter the postorbicular fascial plane. The orbital septum is now seen as a white glistening membrane with yellowish fat behind it. It may be helpful

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to apply gentle pressure to the globe to see the prolapsing fat. The orbital septum is grasped centrally with forceps and cut through with scissors. This allows the preaponeurotic fat pockets to prolapse forward into the wound. To achieve an adequate recession and acceptable cosmetic result, excess preaponeurotic fat should be removed. The interlobular membranes surrounding the fat are gently divided until the fat is fully exposed. The central fat pocket is cauterized along its base and cut with scissors. The medial fat pocket is removed in similar fashion. Laterally, the lacrimal gland lies along the superolateral orbital rim, and in Graves’ patients is frequently prolapsed forward. Care must be taken not to confuse this with fat to be excised. A strip of orbicularis muscle and aponeurosis is cut from along the superior tarsal face. This allows easy identification of Mu¨ller’s muscle at the upper edge of tarsus with the meandering peripheral arterial arcade on its surface. It is useful at this point to inject a small amount of local anesthetic beneath the aponeurosis, into Mu¨ller’s muscle. This not only provides additional comfort to the patient but also makes further dissection easier. With upward traction on the levator aponeurosis, Mu¨ller’s muscle is dissected from the underlying conjunctiva with micro-Westcott scissors (Fig. 4). Mu¨ller’s and conjunctiva are generally highly vascular in Graves’ patients, requiring frequent cautery. The dissection is carried upward to Whitnall’s ligament and the lateral horn is cut where it joins the lateral canthal tendon, to allow better recession of the typical lateral flare seen in Graves’ patients (Fig. 5). Care must be taken to not injure the lacrimal gland ductules, which run in this region. Periodically during the dissection the patient is asked to open his or her eyes to assess the degree of recession. If necessary, the dissection is carried to the level of Whitnall’s ligament. In many cases, even with aggressive disinsertion of Mu¨ller’s muscle and the levator aponeurosis, the eyelid will remain retracted. Here it is important to follow the conjunctiva upward to the fornix and cut the suspensory ligaments that attach to Whitnall’s ligament. These are frequently contracted and will transmit forces from the superior rectus and levator muscles through conjunctiva to the tarsal plate. In this author’s experience, the

Figure 4 Upper eyelid recession with dissection beneath Mu¨ller’s muscle (MM) and the levator aponeurosis (LA).

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Figure 5 Upper eyelid recession shows complete separation of the Mu¨ller’s muscle/ levator complex from the underlying conjunctiva. eyelid should be recessed to a point about 1 mm above the desired final resting position. The aponeurosis does not need to be fixed to the conjunctiva but may be left where it lies. Graves’ patients typically have thickening of the subbrow fat pads, which may extend into the upper eyelid. This contributes to the fullness characteristic of this disease. We prefer to sculpt this fat pad to the level of dermis to achieve a more cosmetically pleasing result. The skin–muscle flap is then advanced downward and excess is marked as for a standard blepharoplasty. This is excised and the wound is closed with any suture of the surgeon’s choice. Iced compresses are applied postoperatively to the eyelids intermittently for 48 h. Antibiotic ointment is placed on the suture line four times daily for 7 days. Because of the inflammatory nature of Graves’ disease, significant postoperative edema and ecchymosis are common. The most frequent complications of upper eyelid recession include overcorrection and undercorrection. With overcorrection, upper eyelid ptosis results from excessive recession of the aponeurosis or a failure to allow for some postoperative drop in eyelid height with return of orbicularis muscle tone. The ptosis can be corrected during the first postoperative week by pulling open the wound and advancing the levator aponeurosis an appropriate amount. This complication is seen in about 20% of cases. Undercorrection may be caused by insufficient recession of the levator aponeurosis and Mu¨ller’s muscle complex, or a failure to separate the lateral horn completely, or to divide adequately the conjunctival fornix suspensory ligaments. If mild, it may be corrected with vigorous downward massage for several weeks. If more than 2–3 mm, how-

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ever, it will require further aponeurotic recession. This is best done during the first postoperative week. V. LOWER EYELID RETRACTOR DISINSERTION WITH SCLERAL GRAFT Lower eyelid recession is the procedure of choice for the correction of functionally or cosmetically significant lower eyelid retraction. In general, inferior scleral show of 1–2 mm can be achieved by retractor tenotomy or simple disinsertion of the lower lid retractors. For greater amounts of recession, a spacer graft is usually required and gives longer lasting results than with tenotomy even with adjunctive antimetabolites (10). It is important to keep mind that in the face of globe proptosis elevating the lower eyelid demands greater eyelid length both horizontally and vertically. Simple eyelid tightening is therefore typically counterproductive and may actually make the retraction worse. This horizontal length disparity must be corrected (11). A traction suture of 4–0 silk is passed through tarsus along the lower eyelid margin, and the lid is everted over a Desmarres retractor to expose the palpebral conjunctiva. The conjunctiva is grasped at the inferior border of the tarsus, and cut through with scissors to reveal the underlying Mu¨ller’s sympathetic muscle, and behind it the capsulopalpebral fascia. The conjunctiva is carefully dissected off the retractors down to the level of Lockwood’s ligament. The capsulopalpebral fascia is then cut from the inferior border of tarsus, and separated from the overlying orbital fat and orbital septum. The medial and lateral attachments of the capsulopalpebral fascia are cut from the canthal tendons, and the retractor is allowed to retract into the orbit. At this point the eyelid can be elevated to just above the inferior corneal limbus, and will not retract on attempted downgaze. The conjunctiva is advanced upward and sutured to the inferior tarsal border. We prefer to put the lower lid on a traction suture for 3 days to allow the anterior and posterior lamellae to fuse without buckling.

Figure 6 Lower eyelid recession with placement of a donor scleral graft to lengthen the eyelid retractors vertically.

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If more than 3 mm retraction is to be corrected, a spacer graft should be placed to lengthen the retractors. A variety of materials are now available, including ear or nasal cartilage, donor sclera, Gortex sheeting, autogenous fascia, donor sclera, and polyethylene discs (12). For ease of use, cost, and consistent results, we prefer the latter. The graft is sutured to the upper edge of the retractors and to the lower border of tarsus with a running stitch of 6–0 vicryl (Fig. 6). It is not necessary to cover the scleral graft with conjunctiva, but we prefer to advance conjunctiva over a cartilage or fascial graft. Polyethylene discs must be buried within the postorbicular fascial plan to prevent erosion. The most common complication of lower eyelid recession is undercorrection. With time, the lid will assume a lower position, so that undercorrection can worsen with time,

(A)

(B)

Figure 7 Results of upper and lower eyelid recession in Graves’ disease. (A) Preoperative appearance. (B) Postoperative result.

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and a small amount of overcorrection is acceptable. Undercorrection will be greater when proptosis is severe, and a larger graft will be necessary to prevent this. In summary, eyelid retraction from Graves’ orbital disease is a significant problem that can result in cosmetic deformity as well as functional complications. While temporary measures can be used to alleviate symptoms, surgical correction provides a permanent cure in the overall rehabilitation of affected patients, providing better eyelid and ocular function as well as improved cosmesis (Fig. 7). Recession must often be combined with orbital decompression and strabismus surgery in a staged approach. REFERENCES 1. Cruz AA, Coleho RP, Baccega A, Lucchzi MC, Souza AD, Ruiz EE. Digital image processing measurement of the upper eyelid contour in Graves’ disease and congenital blepharoptosis. Ophthalmology 1998; 105:913–918. 2. Ozkan SB, Can D, Soylev MF, Arsan AK, Duman S. Chemodenervation in treatment of upper eyelid retraction. Ophthalmologica 1997; 211:387–390. 3. von Brauchitsch DK, Egbert J, Kersten RC, Kulwin DR. Spontaneous resolution of upper eyelid retraction in thyroid orbitopathy. J Neuroophthalmology 1999; 19:122–124. 4. Bodker FS, Putterman AM, Laris A, Miletich DA, Vogel SM, Viana MA. The effect of hyperthyroidism on Mu¨ller’s muscle contractility. Ophthal Plast Reconstr Surg 1997; 13:161–167. 5. Morton AD, Alner VM, Lemke BN, White VA. Lateral extension of the Muller muscle. Arch Ophthalmol 1996; 114:1486–1488. 6. Grove AS Jr. Levator lengthening by marginal myotomy. Arch Ophthalmol 1980; 98:1433. 7. Putterman AM. Surgical treatment of dysthyroid eyelid retraction and orbital fat hernia. Otolaryngol Clin North Am 1980; 13:39. 8. Dutton JJ. Atlas of Oculoplastic Surgery. Eyelid, Orbital, and Lacrimal Surgery. Philadelphia: WB Saunders, 1992. 9. Mourits MP, Sasim IV. A single technique to correct various degrees of upper lid retraction in patients with Graves’ orbitopathy. Br J Ophthalmol 1999; 83:81–84. 10. Oliver JM, Rose GE, Khaw PT, Colin JR. Correction of lower eyelid retraction in thyroid eye diseases: a randomized controlled trial of retractor tenotomy with adjuvant antimetabolite versus scleral graft. Br J Ophthalmol 1998; 82:174–180. 11. Kim JW, Ellis DS, Stewart WB. Correction of lower eyelid retraction by transconjusntival retractor excision and lateral eyelid suspension. Ophthal Plast Reconstr Surg 1999; 15:341– 348. 12. Morton AD, Nelson C, Ikada Y, Elner VM. Porous polyethylene as a spacer graft in thee treatment of lower eyelid retraction. Ophthal Plast Reconstr Surg 2000; 16:146–155.

41 Blepharoplasty in Graves’ Disease STEPHEN J. LAQUIS, BARRETT G. HAIK, and JAMES C. FLEMING University of Tennessee Health Science Center and St. Jude Children’s Research Hospital, Memphis, Tennessee, U.S.A.

I.

INTRODUCTION

Facial changes due to aging are primarily a result of atrophy of body tissues, particularly of the skin, fat, muscle, and their associated connective tissue attachments. Corresponding histological changes include a flattened epidermal–dermal junction, loss of elastic fibers, and decreased collagen fibers (1). There are numerous structural and dynamic changes that the different regions of the aging face undergo. Aging-related changes of the eyelids are of particular concern to most people because the eyes are the central area of focus during human interaction and conversation. Common clinical manifestations of aging eyelids include primarily the formation of periocular rhytids and upper eyelid skin redundancy (Fig. 1). Other signs of the aging eyelid include laxity in the preseptal lid anatomy, including skin and orbicularis muscle, and weakening of the orbital septum, both of which allow prolapse of orbital fat. Furthermore, upper eyelid ptosis, horizontal lower eyelid laxity, and midfacial descent all contribute to the aging appearance of the periocular and midface area (Table 1). Both the rate and clinical evidence of the inevitable aging process vary for each individual and are influenced by a number of factors, including heredity, sun exposure, and smoking. For patients with Graves’ ophthalmopathy, acute and chronic inflammation of the ocular, periocular, and orbital tissues has an additive effect on aging eyelid changes (Fig. 2). In addition, the pathognomonic ‘‘thyroid eye signs,’’ including but not limited to lid retraction and edema, exophthalmos, and extraocular muscle involvement, add a higher level of complexity when one is evaluating these patients for blepharoplasty (Table 2). In this chapter, we discuss the special considerations in preoperative evaluation

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Figure 1 Facial changes due to aging.

Table 1 Eyelid Changes due to Aging Periocular rhytids Upper eyelid skin redundancy Septal laxity/anterior orbital fat prolapse Midfacial descent Brow ptosis Increased lid laxity

Figure 2 Facial changes secondary to Graves’ disease.

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Table 2 Thyroid Eye Changes Acute and chronic inflammation Eyelid retraction Brow fat pad enlargement Increased orbital fat Proptosis causing lid malposition

and operative modifications of which the surgeon should be aware when performing blepharoplasty on a patient with Graves’ eye disease. Unless the goal is to correct progressive exposure keratitis or compressive optic neuropathy, the disease process must be stable for at least 6 months before one performs surgery on patients with Graves’ eye disease. Patients with active or inflammatory disease have variable exophthalmometer and extraocular muscle and eyelid measurements. This variability leads to unpredictable long-term results regardless of technique (2). The degree of proptosis has a direct effect on palpebral fissure height. Also, repositioning of extraocular muscles to correct imbalance, by virtue of the fusion of eyelid retractors to rectus muscle sheaths, also changes eyelid position with resection or recession of these muscles. Thus, lid surgery should be performed only after the palpebral fissure, levator function, and lid-crease height stabilize and after any contemplated surgery that would alter the exophthalmos and extraocular muscles has been performed (3). In summary, after the disease has been established as inactive for 6 months and an acceptable level of decompression and fusion has been obtained, one may then proceed with eyelid adjustment and specifically blepharoplasty, if desired.

II. PATIENT EVALUATION A. History A thorough medical history must include a full systemic and ophthalmic history, current medications, and allergy history. Psychological assessment and a discussion of expectations are especially important in the patient with Graves’ disease. Because of the permanent underlying facial changes associated with this disease, an ideal esthetic outcome and attainment of desired esthetic goals may be more difficult. In addition, the patient should be forewarned that more than one surgical procedure might be necessary in order to achieve the desired result, because of the multifaceted nature of the disorder. B.

Ocular Examination

As part of a thorough ophthalmic exam, basic tear secretion and eyelid closure should be evaluated in all patients being considered for blepharoplasty. A careful corneal exam under high-magnification slit-lamp visualization with fluorescein staining for the presence of superficial punctate keratopathy should accompany tearing and eyelid evaluation, as all three may help detect tear hyposecretion or lagophthalmos. Both of these conditions can be worsened by blepharoplasty and need to be addressed before proceeding with surgery.

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Upper Eyelids

1. Evaluation Evaluation of the eyelids for blepharoplasty in a patient with Graves’ disease should be done in a methodical manner, addressing each ‘‘facial unit’’ individually. Surgical technique may need to be tailored depending on the changes the disease has produced. The authors personally prefer to proceed with evaluation of the periocular facial region from superior to inferior. Each region of the face is addressed individually and related to the eyelids so as not to overlook any subtle but clinically relevant changes. The primary components of the upper eyelid that need to be carefully assessed prior to surgery are the brow position and contour, lid margin to pupillary position (i.e., retraction or ptosis), eyelid contour, dermatochalasis, herniated orbital fat vs. eyelid edema or thickening, and lacrimal gland position (Table 3). Evaluation of the eyebrow is important in the evaluation of any patient seeking blepharoplasty because the position of the brow has a direct effect on the amount of upper eyelid dermatochalasis. Patients with brow ptosis, defined as a distance of less than 10 mm from the central lid margin to the central inferior brow edge (4), may obtain little benefit from blepharoplasty. The excess upper lid skin may arise primarily from a low brow. These patients require brow elevation with or without blepharoplasty. Furthermore, a statistically significant number of people with Graves’ orbitopathy have been shown to have thicker eyebrow fat pads (mean, 1.1 cm) than the normal population (mean 0.5 cm) (5). An excessively thick eyebrow fat pad should be debulked and contoured to match both the shape of the eyelids and the overall facial dimensions during surgery. In a study to define the clinical features of Graves’ ophthalmopathy in an incidence cohort, 108 (90%) of 120 patients had eyelid retraction, making it the most common clinical sign of Graves’ ophthalmopathy (6). Upper eyelid retraction is defined as an elevation of the upper eyelid margin above its normal anatomical position. The upper lid usually sits 1–2 mm below the upper limbal border and 3–5 mm from a centered pupillary light reflex. This latter distance is known as the margin-to-reflex distance-1 (MRD-1). An increase in either of these two parameters indicates upper eyelid retraction. In addition to the evaluation of the extent of eyelid retraction, special attention should be given to the contour of the upper lid. In both the normal upper eyelid and that of the patient with Graves’ disease, the peak of the upper eyelid is found to be lateral to the midline. In Graves’ eyelid retraction, however, the curvature of the upper eyelid is enhanced, the peak of the contour is displaced laterally, and the temporal upper quadrant area is increased (7). Excess eyelid skin should be evaluated, noting the area of most abundant blepharochalasis; removal and contouring of lid skin is based on the areas where most excess skin Table 3 Areas of the Eyelid That Must Be Assessed Prior to Surgery Brow position, contour, and thickness Eyelid margin position Eyelid contour Dermatochalasis Anterior orbital fat prolapse Degree of lid edema

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is present. Furthermore, aggressive excision of excess upper eyelid skin in a patient with Graves’ disease may have untoward consequences. Resultant lagophthalmos is more likely in this population because of underlying lid retraction and proptosis, making corneal decompensation a dreaded but likely complication of blepharoplasty in such patients. It may be necessary to remove prolapsed orbital fat during blepharoplasty to reduce the full or bulging appearance of the lids. Because excess fat removal may result in a sunken-in or enophthalmic postoperative appearance, the surgeon should exercise care in calculating the amount of postseptal fat to be removed. In the patient with Graves’ disease, evaluation of the extent of herniated orbital fat is more difficult because there is an increased secretion of glycoaminoglycans and mucopolysaccharides in orbital and periorbital tissues (8). This leads to a chronically thickened, swollen appearance of the eyelids. In addition, this deposition leads to a fivefold increase in osmotic pressure, sometimes causing chronic edema of the eyelids (9). Careful inspection and palpation of the lid should be performed to differentiate actual fat prolapse from edema or thickening of the eyelid. Ballottement of the eye through closed eyelids can accentuate the protrusion of orbital fat, a maneuver that does not morphologically change thickening or edema in the lid. In assessing fullness of the upper eyelids, special attention should be paid not only to the medial and central fat pads but also to the lateral aspect of the upper lid. Because there is no fat in the superotemporal portion of the upper eyelid, fullness in that area most likely indicates a prolapsed lacrimal gland. If the gland is indeed prolapsed, then it should be resuspended into its fossa under the frontal bone. Failure to do so will lead to persistent fullness in that area after surgery. 2. Surgical Modifications The surgical modification for each area of the upper eyelids is addressed individually. Dissection in the upper eyelid should be performed superiorly in the suborbicularis plane, anterior to the orbital septum towards the brow hair until the brow fat pad is encountered. Excision and contouring of the fat pad should be performed prior to opening the orbital septum and removing preaponeurotic fat. This will differentiate eyelid fullness due to excessive brow fat from anterior herniation of orbital fat (Fig. 3). Failure to note lid elevation prior to blepharoplasty may result in lagophthalmos and corneal decompensation. It is imperative, therefore, that the evaluating physician identify, and correct, lid retraction by any of the surgical techniques, including levator recession (10), Mu¨ller’s muscle excision (11), or a combination of the two (12). It is important to note that although both eyelid retraction surgery and blepharoplasty can be done in the same sitting, the former should be done before the latter because full eyelid closure must be ensured before removing skin from the upper lid. The authors prefer an anterior approach to perform eyelid recession when done in combination with blepharoplasty because a lid crease incision must be made for the latter. This approach can be used to access the levator and Mu¨ller’s muscles easily, while only violating the anterior lamella of the eyelid, thus decreasing the risk for excessive scarring and possible lid contracture. Recession of the lid elevators should be tailored to normalize the temporal flare and, thus, the exaggerated contour of the lid. More aggressive recession of the lateral levator, sometimes including Mu¨ller’s muscle, is necessary to decrease latent lid flare. Cutting the lateral horn of the levator muscle is also helpful to achieve the desired contour. The standard technique of pinching and marking excess eyelid skin for removal may result in overcorrection in the Graves’ patient because the exact tension on the wound is

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Figure 3 A normal brow fat pad contrasted with an enlarged fat pad seen in Graves’ disease prior to contouring.

unknown until after the skin is excised. To assess more accurately the amount of skin that can be removed, the skin muscle flap should first be elevated. An eyelid crease incision is made, and the skin and orbicularis muscle are dissected from their facial attachments. The freely mobile skin–muscle flap is draped inferiorly over the lower edge of the incision with the eye well closed; the desired amount of skin to be removed can then be determined (Fig. 4). This technique improves predictability of the final outcome and decreases the risk of worsening lid retraction or lagophthalmos. As in standard blepharoplasty, the orbital septum is opened to expose the preaponeurotic fat. Ballottement of the globe through the closed lid helps to determine the amount of fat to be resected. In the Graves’ patient, only a conservative amount of fat should be removed. If eyelid fullness is due to edema or lid thickening, ‘‘sculpting’’ of the suborbicularis tissues and orbicularis is done to debulk the lid and soften its appearance. Special care should be taken not to remove excess orbicularis as a weakened closure or a lid too thin for the facial contour may result. Preservation of the lacrimal gland ductules is paramount in patients with Graves’ eye disease because they usually have dry eyes. When suspending the lacrimal gland into its fossa, a permanent periosteal suture, such as a 5–0 nylon, should be used. It is passed in horizontal mattress fashion through only the capsule of the gland with care taken to

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Figure 4 After dissection of the skin-muscle flap in the upper lid, the skin is draped inferiorly to determine the amount of skin that can be safely removed. avoid the ductules. The suture is then passed through the periosteum in the internal aspect of the lateral portion of the supraorbital rim. Tightening of the suture resuspends the gland back into its fossa. D. Lower Eyelids 1. Evaluation The lower eyelid should be addressed in the same systematic manner as the upper lid. The components of the lower lid that need to be examined prior to blepharoplasty in a patient with Graves’ disease are eyelid retraction, horizontal lid laxity, fat herniation, excess skin, and midfacial descent. The selection of technique for lower lid blepharoplasty in Graves’ disease, either transcutaneous or transconjunctival, is individualized and dependent primarily on the findings during preoperative evaluation (13). If excess skin is present, a transcutaneous approach is preferred to a transconjunctival approach. Preexisting lid retraction does not preclude either technique, as correction of retraction can be accomplished either from an anterior or posterior approach. The lower eyelid usually sits at the inferior border of the corneal limbus. An inferiorly retracted lower eyelid allows the inferior sclera of the globe to be seen and is referred to as ‘‘scleral show.’’ The distance between a centered pupillary light reflex and the lower lid margin is known as the margin-to-reflex distance-2 (MRD-2) and is normally between 5 and 7 mm. Both the amounts of ‘‘scleral show’’ and increased MRD-2 are reliable indicators of lower lid retraction. Identification and correction of retraction are essential before proceeding with blepharoplasty; failure to do so may exacerbate the retraction and lead to lagophthalmos and exposure keratopathy. The lower lid support system consists of the tarsoligamentous sling. This structure is defined by the attachments of the lower lid tarsal plate to the medial and lateral canthal tendons and by the insertion of the lower lid retractors to the inferior border of the tarsal plate. The retractor attachments and the amount of tension in the tarsoligamentous sling and overlying pretarsal orbicularis maintain lower lid tone. Disinsertion of lower lid retractors and weakening of the sling’s attachment to the lateral canthal raphe cause lower lid laxity (14). Identification of lower lid laxity can be done by the ‘‘snap back test,’’ in which the lid is pulled inferiorly and anteriorly. If the lid does not return briskly to its

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normal position against the globe, laxity is present. The extent of proptosis is important to note in the evaluation of lid laxity because a more prominent globe displaces the eyelid inferiorly against the more convex portion of the globe. It is important not to overcorrect the laxity in these patients, since horizontal tightening around a prominent globe may force the eyelid margin further inferiorly as the lid is pulled around the convexity of the globe. In assessing fat herniation in the lower lids, it is imperative to palpate the fat pads and to palpate the eye to accentuate protrusion of orbital fat. This helps to differentiate fat herniation from lid edema and thickening in a manner similar to that done in the upper lids. After removal of the fat pads, one may proceed with excess skin removal, if necessary. As with the upper lid, care must be taken not to excise excess skin in the lower lid in order to avoid lower lid retraction postoperatively. A preoperative approximation of the amount of lower lid skin that can be safely excised without causing lower lid retraction is done by placing an index finger on the malar eminence and gently pulling the lower lid and midface inferiorly until the lid margin begins to move. However, to assess more accurately the amount of skin to be removed, intraoperative assessment is necessary. With aging, the midface and cheek complex is displaced inferiorly and medially. This midfacial ptosis may cause inferior displacement of the lower lid systems. In considering blepharoplasty in a patient with Graves’ disease, the position of the midface must be noted. If depressed, this may be addressed by midface elevation or suborbicularis augmentation at the time of lower lid blepharoplasty to further minimize lid retraction postoperatively. 2. Surgical Modifications As in the correction of upper eyelid retraction, correction of the lower lid position can be done using various surgical techniques (15,16). Independent of the technique employed, as in the upper lid, the surgeon should ensure full eyelid closure before proceeding with blepharoplasty. Horizontal shortening procedures may include suspension of the lateral canthus or

Figure 5 The patient is asked to open the eyes and mouth, and the skin of the lower eyelid is stretched. This maneuver allows assessment of the amount of skin that can be safely removed from the lower eyelid.

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Figure 6 Preoperative blepharoplasty photograph of a patient with Graves’ disease. use of the lateral canthal sling or tarsal strip. Regardless of which procedure is employed, lid tightening must be addressed if needed. Failure to correct laxity during blepharoplasty may lead to inferior displacement of the lower lid leading to ectropion or lagophthalmos and exposure keratopathy (17). During fat contouring and removal, care must be taken not to pull or manipulate the fat excessively in order to minimize the risk of avulsing blood vessels which might result in perioperative retrobulbar hemorrhage and potential blindness. Furthermore, aggressive fat removal is discouraged; a resultant tear-through deformity will accentuate any existing proptosis. A skin-muscle flap is then fashioned, and the patient is then asked to open the mouth about two-thirds maximum and look up. This maximally extends the lower lid. The skin is then draped superolaterally over the lower lid, and the correct amount of skin to be removed is determined (Fig. 5). The authors prefer a subperiosteal dissection of the midface as opposed to a dissection under the suborbicular oculi fat pad (SOOF). Anchoring the periosteum of the midface is done to the superolateral portion of the inferior orbital rim by permanent suture fixation. This gives a more permanent elevation and leads to fewer

Figure 7 Postoperative view of the patient in Figure 6.

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drops from opposing gravitational forces. When compared to elevating only the soft tissue of the cheek, which has a tendency to cheese-wire and drop, this technique is superior. III. CONCLUSION Patients with Graves’ disease have many ocular, esthetic, and functional concerns. These concerns can be adequately addressed, first by correcting orbital and extraocular muscle asymmetry and then by eyelid surgery. Blepharoplasty, when done with attention paid to the special anatomical and dynamic changes that the periocular area undergoes, can be very successful and rewarding, both for the patient and the surgeon (Figs. 6, 7). REFERENCES 1. Shewell J, Aston SJ, Thorne CHM: Aesthetic surgery of the aging face. In: Smith JW, Aston SJ, eds. Grabb and Smith’s Plastic Surgery. 4th ed. Boston: Little Brown & Co., 1991:609– 634. 2. Harvey JT, Anderson RL. The aponeurotic approach to eyelid retraction. Ophthalmology 1981; 88:513–524. 3. Frueh BR, Musch CD, Garber FW. Lid retraction and levator aponeurosis defects in Graves’ eye disease. Ophthalm Surg 1986; 17:216–220. 4. Putterman AM: Evaluation of the cosmetic oculoplastic surgery patient. In: Putterman AM, ed. Cosmetic Oculoplastic Surgery. Philadelphia: WB Saunders, 1999:11–22. 5. Goldberger S, Sarraf D, Bernstein JM, Hurwitz JJ. Involvement of the eyebrow fat pad in Graves’ orbitopathy. Ophthal Plast Reconstr Surg 1994; 10:80–86. 6. Bartley GB, Fatourechi V, Kadrmas EF, Jacobsen SJ, Ilstrup DM, Garrity JA, Gorman CA. Clinical features of Graves’ ophthalmopathy in an incidence cohort. Am J Ophthalmol 1996; 121:284–290. 7. Cruz AA, Coelho RP, Baccega A, Lucchezi MC, Souza AD, Ruiz EE. Digital image processing measurement of the upper eyelid contour in Graves disease and congenital blepharoptosis. Ophthalmology 1998, 105:913–918. 8. Hufnagel JT, Hickey WF, Cobbs WH, Jakobiec FA, Iwamoto T, Eagle RC. Immunohistochemical and ultrastructural studies on the exenterated orbital tissues of a patient with Graves’ disease. Ophthalmology 1984; 91:1411–1419. 9. Cooper WC. The surgical management of the lid changes of Graves’ disease. Ophthalmology 1979; 86:2071–2080. 10. Harvey JT, Anderson RL. The aponeurotic approach to eyelid retraction. Ophthalmology 1981; 88:513–524. 11. Putterman AM, Fett DR. Muller’s muscle in the treatment of upper eyelid retraction: a 12year study. Ophthal Surg 1986; 17:361–367. 12. Putterman AM. Surgical treatment of thyroid related eyelid upper eyelid retraction. Graded Muller’s muscle excision and levator recession. Ophthalmology 1981; 88:507–512. 13. Netscher DT, Patrinely JR, Peltier M, Polsen C, Thornby J. Transconjunctival versus transcutaneous lower eyelid blepharoplasty: prospective study. Plast Reconstr Surg 1995; 96:1053– 1060. 14. Hawes MJ, Dortzbach RK. The microscopic anatomy of the lower eyelid retractors. Arch Ophthalmol 1982; 100:1313–1318. 15. Feldman KA, Putterman AM, Farber MD. Surgical treatment of thyroid-related lower eyelid retraction: a modified approach. Ophthal Plast Reconstr Surg 1992; 8:278–286. 16. Small RG, Scott M. The tight retracted lower eyelid. Arch Ophthalmol 1990; 108:438–444. 17. Jordan DR, Anderson RL. The tarsal tuck procedure: avoiding eyelid retraction after lower blepharoplasty. Plast Reconstr Surg 1990; 85:22–28.

42 Somatostatin in the Treatment of Thyroid Eye Disease G. E. KRASSAS Panagia General Hospital, Thessaloniki, Greece

I.

INTRODUCTION

Graves’ orbital disease (GOD) or thyroid eye disease (TED) or thyroid ophthalmopathy (TO) is an inflammatory condition of the orbit, etiologically poorly characterized, that occurs in patients with autoimmune thyroid disease (1,2). It occurs in about 50% of patients with clinically evident Graves’ disease (3). Severe TED occurs in about 3% to 5% of all cases (3). Soft tissues and extraocular muscles of the orbit are involved in the pathogenesis of the disease, which is characterized by enlargement of the extraocular muscles and increase of retrobulbar fat that cause exophthalmos, the main clinical manifestation of the disease. Involvement of cornea, optic nerve and orbital soft tissues may occur during the natural history of the disease (2). During the early stages of the eye condition termed variously Graves’ orbital disease, thyroid eye disease, and thyroid ophthalmopathy (1–4), macrophages, highly specialized T cells, mast cells, and occasional plasma cells infiltrate the orbital connective, adipose, and muscle tissues (5,6). Several cytokines (interferon-γ [IFN-γ] (7), tumor necrosis factor-α [TNF-α], interleukin-1 [IL-1], and transforming growth factor-β [TGF-β] (8,9), as well as growth factors including insulin-like growth factor-1 (IGF-1) and platelet-derived growth factor (PDGF) (10,11), have been detected within the orbital tissues in TED and are now known to be produced both by infiltrating immunocompetent cells and by residential fibroblasts, adipocytes, myocytes, and microvascular endothelial cells. These cytokines and growth factors stimulate cell proliferation, glucosaminoglycan (GAG) synthesis, and expression of immunomodulatory molecules in orbital fibroblasts and microvascular endothelial cells (1,12–14). The finding of the thyroid-stimulating hormone (TSH) receptor in retro-orbital tissue

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may provide the link, previously lacking, between orbital involvement and thyroid pathology in Graves’ disease. Increase in connective tissue and extraocular muscle volume within the bony orbit by accumulating hydrophilic compounds, predominantly GAG, the hydrophilic nature of which can attract water by osmosis, contributes to the clinical manifestation of TED, including exophthalmos, extraocular muscle dysfunction, and periorbital edema (1,2). Graves’ orbital disease evolves through different stages. At the beginning, the retrobulbar space shows a marked lymphocytic infiltration and interstitial edema, whereas in later stages fatty infiltration and fibrosis are observed (1). The identification of patients with TED is based mainly on clinical signs and symptoms affecting one or both eyes (4). Additional information can be obtained from newer imaging techniques, such as magnetic resonance imaging (MRI) or computed tomography (CT), which identify changes in the retrobulbar space such as muscle swelling, edema, and fibrosis (1,15,16). The clinical ocular examination cannot always differentiate the clinically active early stage from the stable fibrotic end stage of the disease. However, this differentiation is crucial in determining which treatment should be given. It has been suggested that immunosuppressive therapy, such as corticosteroids and orbital radiotherapy, is beneficial only in the phase of active inflammation, while rehabilitative surgery (i.e., orbital decompression and eye muscle and lid surgery) should be carried out in the stable end-phase. Imaging techniques (MRI) and laboratory methods (e.g., glycosaminoglycan excretion in urine) have also been applied to evaluate clinical activity of the disease (17,18). Recently [ 111In-DTPA-d-Phe1] octreotide scintigraphy was used in the evaluation of patients with TED (19) and was found to correlate well with clinical activity score CAS and T2 relaxation time of the extraocular rectus muscles (20,21). Orbital pentetreotide accumulation is significantly higher in subjects with active TED; the uptake in the inactive group is close to that in control subjects, in whom no specific uptake is observed (22). These data demonstrate that a positive orbital octreoscan (Fig. 1A) indicates clinically active eye disease in which immunosuppressive treatment might be of therapeutic benefit, in contrast to the fibrotic end stage. Indeed successful immunosuppression with prednisone, orbital irradiation, and intravenous immunoglobulin or very recently with somatostatin analogues, has been found to be associated with a fall in orbital pentetreotide uptake (2,4,22–27) (Fig. 1B). Recent studies have shown successful therapy, with the long-acting somatostatin (SM) analogue octreotide in patients with active TED. The aim of this chapter is to summarize the most recent findings on the usefulness of somatostatin analogues in the medical treatment of TED. II. SOMATOSTATIN AND SOMATOSTATIN RECEPTORS Somatostatin (SM) was originally detected as an inhibitor of the release of growth hormone by the pituitary gland. It is produced in two biologically active forms: a 14 amino acid form (SM-14) and an amino-terminally extended 28 amino acid form (SM-28). SM is found throughout the human body, but mainly within the endocrine glands and nervous system. In the central nervous system (CNS) it can act as a neurohormone and neurotransmitter, whereas in peripheral tissues it regulates endocrine and exocrine secretions and acts as a modulator of motility in the gastrointestinal tract (28). In 1978, Scho¨nbrunn and Tashjian (29) first described SM receptors (SM-Rs) in the rat pituitary tumor cell line GH4C1. The genes for the family of SM-Rs have been cloned in recent years (30). These

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(A)

(B)

Figure 1 (A) Pretherapy, positive octreoscan. (B) Post-therapy octreoscan. genes are located on different chromosomes, but have a high sequence homology (31). Until now, five subtypes of human SM-Rs have been identified, all with a high affinity for SM-14 and SM-28 (32). Different SM-Rs can be expressed in the same tissues in overlapping patterns. All SM-Rs are coupled to G-proteins in the cell membrane and generate a transmembrane signal after binding of SM or SM analogues (SM-a) (33).

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III. CLINICAL USE OF SM ANALOGUES IN THE TREATMENT OF TED Various SM-a have been developed and used in clinical practice because the short halflife of SM-14 makes it unsuitable for routine treatment. The most frequently used SM-a are octreotide and lanreotide. The half-life of octreotide is 90–120 min when administered subcutaneously, and the pharmacodynamic effect lasts for 8–12 h (34). Lanreotide, a new long-acting analogue of SM provided in a slow-release formulation, is more active than natural SM and shows a much longer duration of action. It has been proven to be effective in the treatment of acromegaly and is well tolerated when administered twice or three times per month (35,36). Moreover, the long-acting release formulation of octreotide (Sandostatin-LAR), which has recently become commercially available and can be administered intramuscularly once every 4 weeks, has also been proven to be very effective in suppressing growth hormone (GH) and (IGF-1) in acromegaly (37,38). The effects of octreotide and lanreotide were found to be mediated mainly through SM-Rs subtypes 2 and 5 (32). New subtype-specific SM-a and SM-a antagonists, as well as nonpeptide subtype-specific SM-a, are currently being developed and are of particular interest for clinical application (39). Recent studies have shown successful therapy with octreotide in patients with active TED. Chang et al. (40), in an uncontrolled study, reported that octreotide had a beneficial effect in six patients with TED. In one controlled study (22), we found that octreotide treatment had a beneficial effect in 12 patients with moderately severe TED. Moreover, we showed that the response to low-dosage octreotide treatment (300 µg daily) in these patients was correctly predicted by octreoscan-111. We proposed that octreoscan may predict the effectiveness of treatment with nonradioactive octreotide. However, we have encountered a small number of patients with a negative result on octreoscan who still responded to octreotide therapy. In an uncontrolled study (41), 10 patients were treated with octreotide (0.3 mg/day) for 3 months; although the authors claimed that 8 patients responded to this treatment, a critical reappraisal of their data seems to suggest that no more than 5 patients experienced a real improvement in ocular conditions, proptosis being only minimally affected. This treatment was particularly successful, however, in patients with soft tissue involvement (class II or III) (41). In another uncontrolled study, Kung et al. (42) evaluated the usefulness of octreotide compared with glucocorticoids (GCs.) These authors noted that GCs and octreotide treatment were able to decrease, to a similar extent, the palpebral aperture and activity score after 3 months, but overall activity scores were lower after GCs than after octreotide treatment. In addition, only GC treatment was able to reduce intraocular pressure and muscle size as documented by MRI (42). By contrast, neither octreotide nor GCs significantly improved proptosis, whereas glycosaminoglycan excretion was reduced after both treatments (42). Finally, an absence of a beneficial effect of octreotide treatment was reported by Durak et al. (43) in three patients with active Graves’ ophthalmopathy despite administration of high dosages of the drug (1 mg/day). We administered lanreotide at a dosage of 40 mg every 2 weeks over a period of 3 months to five patients with moderately severe Graves’ ophthalmopathy and a positive octreoscan (24). Four of five patients showed significant improvement of clinical activity score (CAS) in both eyes, and the remaining patient showed improvement in one eye. These data were confirmed in a more recent study in which octreoscan was repeated at the end of the third month of treatment and was found to be negative in all patients (26). Finally, we had the opportunity to treat two girls (ages 14 and 16 years) with moder-


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ately severe TED with SM analogues. Their clinical activity score (CAS) was increased (5 and 6, respectively). Both were receiving antithyroid therapy and were euthyroid at the initiation of treatment. They received 20 mg octreotide (Sandostatin-LAR) intramuscularly in one injection every 30 days, for 4 months. Their ophthalmopathy improved substantially and CAS was decreased in both patients. In view of encouraging therapeutic results in these two juvenile patients, we suggested that SM analogues may prove to be a valuable treatment in children and adolescents with TED, especially in patients for whom glucocorticoid therapy should be avoided or cannot be tolerated (44). Despite these promising results, it must be stressed that most of the studies conducted to date were uncontrolled and have included only small numbers of patients. Thus, a randomized, placebo-controlled prospective clinical study is needed; such a study is currently under way. IV.

MECHANISM OF ACTION OF SM ANALOGUES

The exact mechanism of action of SM-a has not yet been fully clarified. Three main explanations can be offered. First, SM suppresses IGF-1 activity, and inhibition of IGF1-mediated effects may be a promising strategy for controlling the orbital inflammatory process and its deleterious consequences (45). Recent data have demonstrated that orbital lymphocytes and fibroblasts from patients with active TED express IGF-1 receptors and produce IGF-1, which stimulates GAG production and collagen secretion (12,46). Moreover, IGF-1 derived from fibroblasts may inhibit apoptosis in orbital lymphocytes, thereby extending their survival and perpetuating the inflammatory process (46). Furthermore, mitogen-activated human lymphocytes have recently been found to express IGF-2 in addition to IGF-1 receptors and to secrete at least four different IGF-1-binding proteins. The fact that human lymphocytes express receptors for IGF-1 and IGF-2 as well as IGF-1binding proteins suggests that the IGF-1 system may play an important role in human lymphocyte functions. This concept is supported by the fact that SM possesses immunosuppressive qualities and that it modulates the immune response by a variety of different mechanisms, most of which are inhibitory (46,47). A second possible mechanism of action is direct inhibition of the release of lymphokines from T-lymphocytes (48). Cytokines, such as IL-1, IFN-γ, and TNF-α, are known to be produced by orbital macrophages, dendritic cells, and infiltrating activated lymphocytes. These proinflammatory mediators are thought to play an important role in triggering and perpetuating the cascade of reactions that occur in the retro-orbital space of thyroid ophthalmopathy and eventually lead to clinical disease through stimulation of GAG synthesis in orbital preadipocytes and fibroblasts (2,3). In addition, several of these cytokines stimulate the expression of immunomodulatory proteins (human leukocyte antigen-DR, heat shock protein-72, and intercellular adhesion molecules) by orbital fibroblasts, thus aiding in the perpetuation of the autoimmune response in the orbital connective tissue (2,14). In support of this mechanism are the results of a recent study in which we assessed the serum concentrations of TNF-α, intercellular adhesion molecule-1 (sICAM-1), vascular cell adhesion molecule-1 (sVCAM-1), and soluble interleukin-1 receptor antagonist (sIL-1RA) in 23 patients with moderately severe TED and 10 normal controls. Fifteen patients had active eye disease (CAS ⱖ 4 ⫽ PA group) and 8 inactive (CAS ⬍ 3 ⫽ PI group). All PA patients had a positive orbital octreoscan. Six of them received octreotide (300 µg daily subcutaneously) and 9 received lanreotide (30 mg every 10 days intramuscularly). PI patients and controls received neither therapy nor placebo. In the PA group, all

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of the above parameters were again evaluated at 1 and 3 months after initiation of treatment with SM-a. In the PI group, the first measurement was done after 3 months. We observed a significant decrease of CAS in response to treatment. Serum levels of several cytokines and soluble adhesion molecules were elevated in patients with active TED and declined after SM-a treatment, suggesting that SM-a may act, at least in part, by suppressing the release of certain proinflammatory mediators from activated T cells and fibroblasts (G. Krassas et al., unpublished findings.) A third possibility is that SM-a may act directly on target cells through specific cell surface receptors. Gene expression of SM-R 1-5 has been analyzed in various orbital cell types. In these studies, Graves’ orbital lymphocytes were found to express SM-R 1-5 whereas, in TED, orbital adipose tissue RNA encoding SM-R 1-3 and 5 was detected (46,47). In thyroid eye disease, extraocular muscle revealed expression of SM-R-1 and SM-R-2 genes, whereas orbital fibroblasts appear to express SM-R 1-3 but not SM-R-4 or 5 (46). Taken together, these data suggest that SM-a may bind to certain SM-Rs on the surface of various orbital cell types, such as lymphocytes, fibroblasts, and muscle cells, thereby altering their immunological and metabolic activities (47). However, it is likely that SM-a act through a combination of these effects. V.

CONCLUSIONS

Accumulating evidence obtained both in vitro and in vivo now suggests an important role for IGF-1-mediated endocrine, paracrine, and autocrine activity in the evolution and perpetuation of the orbital immune process in TED. The exact mechanism of action of SM analogues has not yet been fully clarified. They may act by suppression of IGF-1 activity and inhibition of IGF-1-mediated effects or by direct inhibition of the release of lymphokines from T lymphocytes. In recent years, several studies have shown promising results with the long-acting SM-a octreotide and lanreotide in patients with active TED. SM-a may provide a valuable, although costly, therapeutic alternative to glucocorticoids, especially in patients who cannot tolerate the latter. Data from prospective placebo-controlled studies with larger numbers of patients are needed, however, before their role in the treatment of TED can be defined. REFERENCES 1. Burch HB, Wartofsky L. Graves’ ophthalmopathy: current concepts regarding pathogenesis and management. Endocr Rev 1993; 14:747–793. 2. Bahn RS, Heufelder AE. Pathogenesis of Graves’ ophthalmopathy. N Engl J Med 1993; 329: 1468–1475. 3. Jacobson DH, Gorman CA. Endocrine ophthalmopathy: current ideas concerning etiology, pathogenesis and treatment. Endocr Rev 1984; 5:200–220. 4. Moncayo R, Baldnisera I, Decristoforo C, Kendler D, Donnemiller E. Evaluation of immunological mechanisms mediating thyroid-associated ophthalmopathy by radionuclide imaging using the somatostatin analog 111In-octreotide. Thyroid 1997; 7:21–29. 5. Tallstedt L, Norberg R. Immunohistochemical staining of normal and Graves’ extraocular muscle. Invest Ophthalmol Vis Sci 1988; 29:175–184. 6. Perros P, Kendall-Taylor P. Pathogenesis of thyroid-associated ophthalmopathy. Trends Endocrinol Metabol 1993; 4:270–275. 7. Smith TJ, Bahn RS, Gorman CA, Cheavens M. Stimulation of glycosaminoglycan accumula-


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29. Schonbrunn A, Tashjian H Jr. Characterization of functional receptors for somatostatin in rat pituitary cells in culture. J Biol Chem 1978; 213:6473–6483. 30. Humphrey P, Reisine T. Somatostatin receptor nomenclature consensus. Ciba Found Symp 1995; 190:261–262. 31. Patel YC, Greenwood M, Panetta R, Hukovic N, Grigorakis S, Robertson LA, Srikant CB. Molecular biology of somatostatin receptor subtypes (review). Metabolism 1996; 45:31–38. 32. Patel YC, Srikant CB. Subtype selectivity of peptide analogs for all five cloned human somatostatin receptors (SSTr 1–5). Endocrinology 1994; 135:2814–2817. 33. Florio T, Schettini G. Multiple intracellular effectors modulate physiological functions of the cloned somatostatin receptors. J Mol Endocrinol 1996; 17:89–100. 34. Pless J. Chemistry and pharmacology of sandostatin. Z Gastroenterol 1990; 28 (suppl. 2):4– 7. 35. Caron P, Morange-Ramos I, Cogne M, Jaquet P. Three years follow-up of acromegalic patients treated with intramuscular slow-release lanreotide. J Clin Endocrinol Metab 1997; 82:18–22. 36. Colao A, Marzullo P, Ferone D, Marino V, Pivonello R, Di Somma C, Di Sarno A, Giaccio A, Lombardi G. Effectiveness and tolerability of slow release lanreotide treatment in active acromegaly. J Endocrinol Invest 1999; 22:40–47. 37. Flogstad AK, Halse J, Bakke S, Lancranjan I, Marbach P, Bruns C, Jervell J. Sandostatin LAR in acromegalic patients: long term treatment. J Clin Endocrinol Metab 1997; 82:23–28. 38. Newman CB, Melmed S, George A, Torigian D, Duhaney M, Snyder P, Young W, Klibanski A, Molitch ME, Gagel R, Sheeler L, Cook D, Malarkey W, Jackson I, Vance ML, Barkan A, Frohman L, Kleinberg DL. Octreotide as primary therapy for acromegaly. J Clin Endocrinol Metab 1998; 83:3034–3040. 39. Rohrer SP, Birzin ET, Mosley RT, Berk SC, Hutchins SM, Shen DM, Xiong Y, Hayes EC, Parmar RM, Foor F, Mitra SW, Degrado SJ, Shu M, Klopp JM, Cai SJ, Blake A, Chan WW, Pasternak A, Yang L, Patchett AA, Smith RG, Chapman KT, Schaeffer JM. Rapid identification of subtype-selective agonists of the somatostatin receptor through combinatorial chemistry. Science 1998; 282:737–740. 40. Chang TC, Kao SCS, Huang KM. Octreotide and Graves’ ophthalmopathy and pretibial myxoedema. Br Med J 1992; 304:158. 41. Ozata M, Bolu E, Sengul A, Tasar M, Beyhan Z, Corakci A, Gundogan MA. Effects of octreotide treatment on Graves’ ophthalmopathy and circulating sICAM-1 levels. Thyroid 1996; 6: 283–288. 42. Kung AWC, Michon J, Tai KS, Chan FL. The effect of somatostatin versus corticosteroid in the treatment of Graves’ ophthalmopathy. Thyroid 1996; 6:318–324. 43. Durak I, Durak H, Ergin M, Yurekli Y, Kaynak S. Somatostatin receptors in the orbits. Clin Nucl Med 1995; 20:237–242. 44. Krassas GE. Thyroid eye disease in children and adolescents—new therapeutic approaches. J Pediatr Endocrinol Metab 2001; 14:97–100. 45. Hansson HA, Petruson B, Skottnerm A. Somatomedin C in pathogenesis of malignant exophthalmos of endocrine origin. Lancet 1986; 1:218–219. 46. Heufelder AE. Somatostatin analogues in Graves’ ophthalmopathy. J Endocrinol Invest 1997; 20 (suppl. 7):50–52. 47. Krassas GE. Somatostatin analogues in the treatment of thyroid eye disease. Thyroid 1998; 8:443–445. 48. Malec P, Zeman K, Markiewicz K, Tchorzewski H, Nowak Z, Baj Z. Short term somatostatin infusion affects T-lymphocyte responsiveness in humans. Immunopharmacology 1989; 17: 45–49.

43 Pentoxifylline in the Management of Thyroid Eye Disease CSABA BALA´ZS Kene´zy Teaching Hospital, Debrecen, Hungary

I.

IMMUNOMODULATING EFFECTS OF PENTOXIFYLLINE

Pentoxifylline (Ptx) (1-/5-oxohexyl)-3,7-dimethylxantine) has been widely used for the treatment of chronic occlusive arterial disease because of its rheological action. The effectiveness of this drug has been attributed to its influence on erythrocyte deformability, platelet reactivity and plasma viscosity, and prostacycline release (1). Like other methylxanthines, Ptx inhibits phosphodiesterase, resulting in a significant increase of intracellular cyclic adenosine monophosphate (cAMP), which is known to modulate a number of cellular immune functions (2,3). It has been reported that Ptx is able to inhibit inflammatory processes including phagocytosis and superoxide anion and nitric oxide (NO) production by polymorphonuclear granulocytes and monocytes (4,5). This drug has also been reported to affect T lymphocytes by modulating production of various cytokines involved in immune and autoimmune reactions (6–9). Recently, the immunomodulating effects of Ptx were investigated in a randomized double-blind study comparing Ptx with placebo in 140 patients receiving cadaveric kidney grafts under cyclosporine and prednisolone treatment. Ptx weakened the consequences of rejection on graft survival and this phenomenon was mediated by reduction of tumor necrosis factor α (TNF-α) in sera of patients receiving transplants (10–12). Furthermore, Ptx influenced cytokine-induced fibroblast proliferation. Ptx exerted a robust inhibitory effect on fibroblast proliferation, extracellular matrix synthesis, and myofibroblast differentiation (13). Thyroid-associated orbitopathy (TAO) is considered to be a genetically determined autoimmune disorder that occurs by infiltration of lymphocytes and enlargement of extraocular muscle, accumulation of glycosaminoglycan (GAG) resulting a clinical manifestation of edema, proptosis, diplopia, and optical nerve compression (14–17). The activated 441

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lymphocytes have been shown to secrete several cytokines including TNF-α, interleukin1 (IL-1), and interferon gamma (IFN-γ), which are able to express HLA-DR antigens and stimulate fibroblats to proliferate, produce GAG and free oxygen radicals (15,16). In addition, the predominance of a Th1 profile of cytokine production was found in retrobulbar tissue of patients with TAO (15). The cytokines can result in induction and perpetuation of autoimmune processes in the retrobulbar tissues. Although, immunological studies have improved our knowledge of the pathomechanism of TAO, we remain limited in our ability to treat this disease effectively. Various therapeutic interventions have been known to modify the production of cytokines. Anticytokine antibodies and IL-1 receptor antagonists were reported to inhibit the GAG synthesis of retrobulbar fibroblasts (REF). Furthermore, it was recently observed that superoxide radicals generated in culture media were able to stimulate REF. Methimazole as a free radical scavenger drug inhibited superoxideinduced proliferation in a dose-dependent manner (17–23). The different methods and drugs used for treatment of TAO are not able to cure completely the inflammatory symptoms of TAO, have potential serious side effects, and often prove to be very expensive. Therefore, an effort has been made to find new cytokine antagonists interfering with cytokine synthesis, receptor binding, or signal transduction (24). Ptx appeared to be an effective and inexpensive drug that can modulate the autoimmune processes in patients with TAO, and proved to be a promising agent for relief of inflammatory symptoms (19,25).

II. IN VITRO STUDIES OF PENTOXIFYLLINE ON RETROBULBAR FIBROBLASTS A.

Effect of Ptx on Spontaneous and Cytokine-Induced GAG Synthesis

Ptx significantly decreases the spontaneous GAG synthesis of REF at 500 and 1000 mg/L. In addition, TNF-α (100 U/mL), IL-1 (100 U/mL), and IFN-γ (100 U/mL) induce a remarkable increase in GAG production by REF in culture. Both TNF-α- and IFN-γ-induced GAG synthesis is significantly inhibited by Ptx (19). Ptx abolishes virtually completely the enhancing effects of TNF-α and IFN-γ on GAG synthesis by REF. Furthermore, exposure of cultures to Ptx resulted in a dose-dependent inhibition of IL-1-induced GAG synthesis as well. B.

Effect of Ptx on HLA-DR Induction

It is known that on the surface of REF only the molecules of major histocompatibility complex (MHC) class I antigens can be detected. Immunhistochemical investigations have demonstrated the expression of MHC class II/HLA-DR molecules on the surface of REF from patients with TAO. The expression of HLA-DR molecules appears to be a key factor in the induction and perpetuation of autoimmune processes (19,26). Some cytokines are also known to result in HLA-DR expression on the surface of thyrocytes and REF (7,19,2). We investigated the IFN-γ-induced HLA-DR expression in cultures of REF. These in vitro studies indicated that IFN-γ at 50, 100, and 500 U/mL added to cultures of REF caused a significant increase in the number of HLA-DR-positive cells (26.5 ⫾ 4.5%, 45.7 ⫾ 11%, and 61.9 ⫾ 15.9%, respectively). Ptx alone (10–1000 mg/L) had no effect on spontaneous expression of HLA-DR molecules on REF. Ptx, however, was able to inhibit dose-dependently HLA-DR expression on the surface of REF induced by IFN-γ (100 U/mL) (14).

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Furthermore, we found that this inhibitory effect of Ptx cannot be attributed to Ptx cytotoxicity, since cell viability was not significantly decreased by the drug added to cultures. III. IN VIVO OBSERVATIONS ON EYE SYMPTOMS OF PATIENTS WITH TAO TREATED WITH PENTOXIFYLLINE Preliminary in vitro experimental studies and in vivo studies on the effects of pentoxifylline in patients with TAO have been reported (26,27). Thirty-one patients (28 women, 3 men) with moderately severe TAO and of average age 41 ⫾ 4.8 years were selected from 221 patients with Graves’ disease. They were excluded from steroid treatment because of severe peptic ulcer, non-insulin-dependent diabetes mellitus, glaucoma, and psychiatric diseases. All patients were treated with methimazole at an average dosage of 25 ⫾ 2.6 mg/day. At the time of Ptx therapy all patients had been euthyroid for at least 4–6 weeks. The diagnosis of TAO was based on typical clinical features and ophthalmic B scan and computer tomography. Eye changes were classified according to American Thyroid Association criteria and as described by Mourits et al. (28,29). Moderately severe TAO was defined as one or more of the following NOSPECS categories: class 2, grade b or c; class 3, all grades; class 4, all grades. Patients in class 5 and class 6 were considered to have disease too severe to include in this study. Ptx was initially given intravenously (200 mg/ day) for 7 days. Therapy then continued orally at 1800 mg/day for the first 4 weeks and was decreased to 1200 mg/day (3 ⫻ 400 mg/day). To complete the quantification of degree of response, we used ‘‘total eye score’’ (TES) (29) for each subject by multiplying each NOSPECS class present by the grade in that class (we substituted 1, 2, and 3, respectively, for grades a, b, and c). We followed up the eye clinical symptoms and some laboratory data including TNF-α in the patients’ blood during treatment. We found an impressive beneficial effect of Ptx therapy after 12 weeks in 27 of 31 patients. The effect of Ptx therapy was significant in the reduction of soft tissue involvement. There was a less significant improvement in proptosis and extraocular muscle involvement (Figs. 1, 2). We saw no improvement in four patients, and these were considered nonresponders. The Ptx treatment had only few side effects including nausea and stomach ache, but it was not necessary to interrupt therapy. Serum TNF-α levels that proved to be higher before treatment became progressively lower in responders (Fig. 3). After 4, 8, and 12 weeks of Ptx treatment there was a significant decrease in TNF-α level of responders. However, in nonresponders, serum levels of TNF-α (before therapy 35 ⫾ 7.4 pg/mL) were not decreased significantly at the end of the period of observation (31 ⫾ 5.9 pg/mL). In addition, the level of GAG, which is deemed to be a useful marker for TAO activity, was significantly higher in patients with TAO than in controls (26). A significant decrease in levels of GAG in responders was apparent by 4 weeks. The reason for the lack of effect of Ptx in four patients is not known. The pharmacokinetics of Ptx is critical, because the low level of this drug might be responsible for its ineffectiveness. Animal studies showed that Ptx was rapidly absorbed and eliminated after oral administration. In dogs, oral administration of 15 mg Ptx/kg results in plasma concentrations similar to those produced by therapeutic doses in humans. Three times daily dosing is recommended. It is noteworthy that higher plasma Ptx concentrations and apparent bioviability were observed after oral administration of the first dose, compared with the last dose during a 5-day treatment regimen (20). It is also possible that an increased turnover of this drug occurs in some tissues due to pharmacogenetic factors and a more rapid elimination might be responsible for the lack of response in some patients.

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Figure 1 Grades with NOSPECS classes at the beginning (week 0) and at the end of the study (week 12) in 31 patients treated with pentoxifylline.

Figure 2 Integrated total eye scores (TES) of 31 patients (nonresponders and responders) treated with pentoxifylline. Open bars, TES before therapy; hatched bars, after 4 weeks; cross bars, after 8 weeks; black bars, after 12 weeks of therapy.


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Figure 3 Changes of TNF-α in patients treated with pentoxifylline. The level of TNF-α in 31 patients with TAO was significantly higher (p ⬍ 0.001) than controls. Black bars, decrease of TNF-α in sera of responders to Ptx treatment; open bars, levels of TNF-α in nonresponders * ⫽ p ⬍ 0.05; ** ⫽ p ⬍ 0.001.

These encouraging observations must be tempered by the fact that the cohort of patients was relatively small. Undoubtedly, the exact relevance of Ptx therapy needs to be confirmed by a randomized trial. The problem is that both traditional and Ptx therapy are effective mostly in the acute inflammatory phase of TAO. Unfortunately, due to ethical reasons the randomized trial of Ptx has not been possible before now. An international cooperative clinical evaluation is needed to determine the effectiveness and indications for Ptx treatment. Finally, it is concluded that Ptx may be an effective therapeutic modality that can significantly decrease the inflammatory symptoms of patients with TAO by itself or in combination with other drugs. ACKNOWLEDGMENT This work was supported by a grant from the Hungarian Ministry of Health (ETT61001/2000). REFERENCES 1. Gonzalez-Amaro R, Portales-Pe´rez D, Baranda L, Rodondo JM, Martinez-Martinez S, YanezM, Garcia-Vicuna R, Cabanas C, Sanches-Madrid F. Pentoxifylline inhibits adhesion and activation of human T lymphocytes. J Immunol 1998; 161:65–72. 2. Samlaska CP, Winfield EA. Pentoxifylline. J Am Acad Dermatol 1994; 30:603–621. 3. van Leenen D, van der Poll T, Levi M, tenCote H, van-Deventer SJ, Hack CE, Aarden LA, ten-Cate JW. Pentoxifylline attenuates neutrophil activation in experimental endotoxemia in chimpanzees. J Immunol 1993; 151:2318–2325. 4. Beshay E, Croze F, Prud’homme GJ. The phosphodiesterase inhibitors pentoxifylline and Rolipam suppress macrophage activation and nitric oxide production in vitro and in vivo. Clin Immunol 2001; 98:272–279. 5. Neuner P, Klosner G, Schauer E, Puormojib M, Machener W, Grunwald G, Knobler R,

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Bala´zs Schwarz A, Lugez TA, Schwartd T. Pentoxifylline in vivo down-regulates the release of IL1 beta, IL-6, IL-8 and TNF-alpha by human peripheral blood mononuclear cells. Immunology 1994; 83:262–267. Neuner P, Klosner G, Pourmojib M, Knobler R, Schwarz T. Pentoxifylline in vivo and in vitro down-regulates the expression of the intercellulars adhesion molecule-1 in monocytes. Immunology 1997; 90:345–439. Bala´zs Cs, Kiss E. Immunological aspects of the effect of pentoxifylline (Trental). Acta Microbiol Immunol Hung 1994; 41:121–226. Doherty GM, Jensen JC, Alexander HR, Buresh CM, Norton JA. Pentoxifylline suppression of tumor necrosis factor gene transcription. Surgery 1991; 110:192–198. Krakauer T. Pentoxifylline inhibits ICAM-1 expression and chemokine production induced by proinflammatory cytokines in human pulmonary epithelial cells. Immunopharmacology 2000; 46:253–261. Hewitson TD, Martic M, Kelynack KJ, Pedagogos E, Becker GJ. Pentoxifylline reduces in vitro renal myofibroblast proliferation and collagen secretion. Am J Nephrol 2000; 20:82–88. Strutz F, Heeg M, Kochsiek T, Siemers G, Zeisberg M, Muller GA. Effects of pentoxifylline on proliferation, differentiation and matrix synthesis of human renal fibroblasts. Nephrol Dial Transplant 2000; 10:1535–1546. Noel C, Copin MC, Hazzan M, Labalette M, Susen S, Lelievre G, Dessaint JP. Immunomodulatory effect of pentoxifylline during human allograft rejection: involvement of tumor necrosis factor-alpha and adhesion molecules. Transplantation 2000; 69:1102–1107. Duncan MR, Hasan A, Berman B. Pentoxifylline, pentoxifylline and interferons decrease Type I and III procollagen mRNA levels in dermal fibroblasts: evidence for mediation by nuclear factor 1 down-regulation. J Invest Dermatol 1995; 104:282–286. Wall J, Kennerdell JS. Progress in thyroid-associated ophthalmopathy. Autoimmunity 1995; 22:191–195. Weetman AP. Graves’disease. N Engl J Med 2000; 343:1236–1248. Kahaly G, Hansen CH, Felke B, Dienes HP. Immunohistochemical staining of retrobulbar adipose tissue in Graves’ ophthalmopathy. Clin Immunol Immunopathol 1994; 73:53–62. Frecker M, Stenszky V, Bala´zs Cs, Kozma L, Kraszits Z, Farid NR. Genetic factors in Graves’ ophthalmopathy. Clin Endocrinol 1986; 6:190–192. Kahaly G, Hansen C, Beyer J, Winand R. Plasma glycosaminoglycans in endocrine ophthalmopathy. J Endocrinol Invest 1994; 17:45–50. Bala´zs Cs, Kiss E, Farid NR. Inhibitory effect of pentoxifylline on HLA-DR expression and glycosaminoglycan synthesis by retrobulbar fibroblasts. Horm Metab Res 1998; 30:496–499. Bartalena L, Marcocci C, Pinchera A. Cytokine antagosits: new ideas for the management of Graves’ ophthalmopathy J Clin Endocrinol Metab (Editorial). 1996; 81:446–447. Bala´zs Cs, Kiss E, Leo¨vey A, Farid NR. The immunosuppressive effect of methimazole on cell-mediated immunity is mediated by its capacity to inhibit peroxidase and to scavenge free oxigen radicals. Clin Endocrinol 1986; 25:7–12. Burch HB, Lahiri S, Barnes SG. The effect of methimazole and antioxidants on superoxide radical-induced retroocular fibroblasts proliferation. Thyroid 1996; Suppl. 6:1–7. Tan GH, Dutton CM, Bahn RS. Interleukin-1 (IL-1) receptor antagonists and soluble IL-1 receptor inhibit IL-1-induced glycosaminoglycan production in cultured human orbital fibroblasts from patients with Graves’ ophthalmopathy. J Clin Endocrinol Metab 1996; 81:449– 452. Wiersinga W, Prummel MF. An evidence-based approach to the treatment of Graves’ ophthalmopathy. Endocrinol Metabol Clin North Am 2000; 29:297–319. ´ , Molna´r I, Farid NR. Beneficial effect of pentoxifylline on thyroid Bala´zs Cs, Kiss E, Va´mos A associated ophthalmopathy (TAO): a pilot study. J Clin Endocrinol Metab 1997; 82:1999– 2002.


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26. Bodolay E, Szegedi Gy, Surańyi P, Juha´sz F, Stenszky V, Bala´zs Cs, Farid NR. Expression of HLA-DR antigens by thyroid cells: effect of Graves’ IgG. Immunol Lett 1987; 15:77–81. 27. Bala´zs Cs, Farid NR. Effect of pentoxifylline on thyroid associated ophthalmopathy. Fifth European Endocrine Congress, Turin, June 12–14, 2001. 28. Werner SC. Modification of the classification of the eye changes of Graves’ disease: recommendation of the Ad Hoc Committee of American Thyroid Association. J Clin Endocrinol Metab 1977; 44:203–204. 29. Mourits MP, Koornneef L, Wiersinga WM, Prummel MF, Bergout AS, Gaag RD. Clinical criteria for assessment of disease activity in Graves’ ophthalmopathy: a novel approach. Br J Ophthalmol 1989; 73:639–647. 30. Marsella R, Nicklin CF, Munson JW, Roberts SM. Pharmacokinetics of pentoxifylline in dogs after oral and intravenous administration. Am J Vet Res 2000; 61:631–637.

44 Engineering a Soluble Human Thyroid-Stimulating Hormone Receptor Protein GREGORIO D. CHAZENBALK Cedars-Sinai Medical Center and University of California, Los Angeles, California, U.S.A.

The thyrotropin receptor (TSHR) not only plays a crucial role in thyroid physiology but also is the main antigen directly involved in the pathogenesis of Graves’ disease (reviewed in ref. 1). TSHR belongs to the family of G protein-coupled receptors with a large ectodomain region and a serpentine region that transverses the plasma membrane seven times (2–5). Regarding its subunit structure, the TSHR is the only member of the glycoprotein hormone receptor that cleaves on the cell surface of mammalian cells into two subunits: an A subunit present within the ectodomain region linked by disulfide bonds to a B subunit (6–8). The TSHR ectodomain is highly glycosylated (9) and contains the binding sites for the thyroid-stimulating hormone (TSH) as well as for stimulating and blocking TSHR autoantibodies (10,11). These binding sites involve mutiple and discontinous regions throughout the ectodomain (10,11). A better understanding of the interaction between the TSHR and its autoantibodies will help to elucidate the mechanisms involved in Graves’ disease. For this reason, the availability of large amounts of pure, conformationally intact TSHR is essential. After many years of effort, it is now possible to produce large amounts of TSH holoreceptor in myeloma cells (12), in Chinese hamster ovary (CHO) cells after transgenome amplification (13), in HeLa cells after vaccinia virus infection (14), and K562 leukemia cells (15). However, the hydrophobic membrane-spanning segments present in the protein make its purification extremely difficult. The TSHR ectodomain is more hydrophilic and carries the advantage of generating a more soluble protein capable of ligand and autoantibody recognition. Nevertheless, the 449

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TSHR ectodomain is expressed in prokaryotes as insoluble inclusion bodies (8,16–19). In order to obtain a soluble protein it was necessary to use chaotropic reagents, which cause an irreversible denaturation of the protein. A soluble form of the TSHR ectodomain was generated using maltose binding protein (pMAL) or glutathione-S-transferase (GST) expression vectors (20,21). Some reports have indicated specific interaction between the deglycosylated protein and TSHR autoantibodies (18,19,21). Different groups have expressed the TSHR ectodomain in a cell free-translation system. However, the interaction between the material produced and TSHR autoantibodies has produced conflicting results (22,23). Eukaryotic insect cells infected with a baculovirus transfer vector were also used to generate large amounts of glycosylated TSHR ectodomain. By using conventional baculovirus vectors, the TSHR ectodomain was expressed as insoluble protein (24–27). A more heavily glycosylated protein was generated using a signal peptide from the baculovirus expression vector instead of the TSHR signal peptide. This protein was, however, still insoluble (28,29). The TSHR ectodomain was also expressed with an earlier baculovirus promoter (30). Most of this material remained inside the cells as immature, high-mannose form (29–30), probably due to abnormal folding and trafficking. Only a tracer amount neutralized completely TSHR autoantibodies present in patient’s sera (29,30). An alternative approach to generate a fully glycosylated and secreted TSHR ectodomain would be by expressing this protein in mammalian eukaryotic cells. For this purpose, a stop codon was introduced at the entry position of the TSHR ectodomain into the plasma membrane (31). After transgenome amplification in CHO cells, large amounts of soluble TSHR ectodomain remained inside the cells containing immature high-mannose carbohydrate (31,32). Again a failure of this protein to fold correctly may cause retention in the endoplasmic reticulum in a high-mannose form. Only a minute amount of mature TSHR ectodomain was detected, capable of neutralizing TSHR autoantibodies present in the sera of patients with Graves’ disease (31). Taking into account all these difficulties in generating a secreted TSHR ectodomain, we decided to express the A subunit rather than the whole ectodomain, hypothesizing that this approach would generate a secreted protein. Based on the presence of three potential cleavage sites, characterized by clusters Arg and Lys residues (33) we performed progressive carboxy terminal truncations of the TSHR ectodomain, at residues 261, 289, and 309. Six histidine residue tags at the C termini followed by stop codon were also inserted (Fig. 1). These three ectodomain variants (TSHR-261, TSHR-289, and TSHR-309) were secreted with an efficacy inversely proportional to their size (34). All three ectodomain variants contained complex carbohydrate, and neutralized autoantibodies in Graves’ patients’ sera (34). TSHR-261 and TSHR-289 were partially purified using lectin and nickel– chelate chromatography. Nanogram amounts of this material neutralized completely or almost completely TSHR autoantibodies in Graves’ sera (34). These results indicated that TSHR autoantibody concentration is very low, in the range of nanograms per milliliter. The bioactivity of TSHR-261 and TSHR-289 was quite similar in terms of their ability to neutralize TSHR autoantibodies, but there was no interaction with TSH (34). Although TSHR-261 is the most secreted TSHR ectodomain variant, its bioactivity diminished at room temperature with time. Therefore, we decided to work with TSHR-289, which is more stable. The availability of partial purified TSHR-289 allowed us to generate a mouse monoclonal antibody, 3BD10, which recognized a conformational epitope located at the extreme N-terminus of TSHR (35). This region is highly conformational due to the presence of a cluster of four cysteine residues that probably are paired by disulfide bonds (reviewed in Ref. 1). The 3BD10 epitope overlaps with part of a conformational epitope

Soluble Human TSH-Receptor Protein

451

Figure 1 Schematic representation of three TSHR ectodomain variants progressively truncated at their carboxyl-terminal region. Six histidine residues (6H) at the C-termini followed by a stop codon were also introduced after the indicated amino acid residues. (From Ref. 34.) for TSHR autoantibodies (35). Because monoclonal antibody (mAb) 3BD10 mainly recognized TSHR-289 under native conditions (35), a 3BD10 affinity columm was used to extract TSHR-289 from cultured medium. Unfortunately, the extracted protein did not interact with TSHR autoantibodies (inactive form) (36). TSHR-289 that was not retained by the 3BD10 affinity column was capable of neutralizing TSHR autoantibodies (active form), which could be purified by using a second affinity columm with a mAb to the Cterminal histidine residues (Fig. 2). These two forms were purified to near homogeneity, with a similar yield for both (⬃0.5–0.7 mg/L cultured medium) (36). TSHR-289, both immunologically active and inactive, had the same primary amino acid sequence and carbohydrate content (36). Most likely, a subtle change in protein folding at the N-terminus region (3BD10 epitope) would explain the difference in bioactivity between these two forms (Fig. 3). Immunologically active TSHR-289 lost the ability to recognize TSHR autoantibodies after a few hours at 37°C (36). Nevertheless, stabilization of active TSHR289 was achieved by the action of the chemical chaperones proline and trimethylamine N-oxide at very high concentrations (36). The accessibility in the cultured medium of secreted TSHR-289, without further purification, allowed us to develop a direct TSHR autoantibody assay (37). A very good correlation was observed between this direct-binding assay and the classic thyrotropinbinding inhibition assay (TBI) (37). These data indicated that most of the autoantibodies that bind to the TSHR also inhibit TSH binding (37,38). Turning back to the whole TSHR ectodomain, various groups have only recently, succeeded in the expression of biologically active protein. TSHR ectodomain was anchored to the CD8 transmembrane region with a thrombin cleavage site inserted at the junction between both regions (38). After thrombin treatment, the TSHR ectodomain was released as a soluble protein capable of binding TSH and TSHR autoantibodies (39,40). The TSHR ectodomain was also expressed as a glycosylphosphatylinositol (GPI)-an-

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Figure 2 Separation and purification of the immunologically active and inactive forms of TSHR-289. Conditioned medium from CHO cells expressing TSHR-289 was applied to two mAb affinity columns connected in series. Active and inactive forms of TSHR-289 were obtained after elution from the anti-his and the 3BD10 affinity columns, respectively. (From Ref. 36.)

Figure 3 Subtle differences in protein folding between active and inactive forms of TSHR-289. This hypothetical model shows a cluster of four cysteine residues, Cys 24, 29, 31, and 41, at the N-terminus region, that are likely to form disulfide bonds. Difference between active and inactive forms of TSHR-289 could be due to change in folding in this high conformational region.


453

chored membrane protein (41,42). This protein was expressed on the cell surface of CHO cells at much higher levels than the full-length TSHR. Soluble TSHR ectodomain released by GPI-specific phospholipase C interacted specifically with TSH and TSHR autoantibodies (42). The bioactivity of TSHR ectodomain in terms of TSH binding was stabilized by the presence of mouse monoclonal antibody that recognized a conformational epitope on the TSHR ectodomain (42). In conclusion, since the molecular cloning of the human TSHR, many attempts to generate large amounts of secreted and functional TSHR ectodomain have failed. Nevertheless, by progressive carboxyl truncations of human TSHR ectodomain it was possible to generate secreted proteins with complex carbohydrate that neutralizes TSHR autoantibodies present in Graves’ patient’s sera. One of these TSHR ectodomain variants, TSHR289, could be purified as an immunologically active and stable antigen. In addition, a soluble TSHR whole ectodomain was generated after releasing the protein previously fused to either the single transmembrane domain of CD8 or the GPI moiety. The TSHR ectodomain bound specifically TSH and TSHR autoantibodies. The availability of large amounts of immunologically active and stable TSHR-289 opens the way to accomplish very important goals: determination of its three-dimensional structure, which will give invaluable information about the interaction between the antigen and TSHR autoantibodies; the molecular cloning of human TSHR autoantibodies; and the development of a very sensitive assay for the direct detection of TSHR autoantibodies. REFERENCES 1. Rapoport B, Chazenbalk GD, Jaume JC, McLachlan S. The thyrotropin receptor: interaction with TSH and autoantibodies. Endocr Rev 1998; 19:673–716. 2. Parmentier M, Libert F, Maenhaut C, Lefort A, Gerard C, Perret J, Van Sande J, Dumont JE, Vassart G. Molecular cloning of the thyrotropin receptor. Science 1989; 246:1620–1622. 3. Nagayama Y, Kaufman KD, Seto P, Rapoport B. Molecular cloning, sequence and functional expression of the cDNA for the human thyrotropin receptor. Biochem Biophys Res Commun 1989; 165:1184–1190. 4. Libert F, Lefort A, Gerard C, Parmentier M, Perret J, Ludgate M, Dumont JE, Vassart G. Cloning, sequencing and expression of the human thyrotropin (TSH) receptor: evidence for binding to autoantibodies Biochem Biophys Res Commun 1989; 165;1250–1255. 5. Misrahi M, Loosfet H, Atger M, Sar S, Guiochon-Mantel A, Milgrom E. Cloning, sequencing and expression of human TSH receptor. Biochem Biophys Res Commun 1990; 166:394–403. 6. Buckland PR, Rickards CR, Howells RD, Jones ED, Rees Smith B. Photo-affinity labelling of the thyrotropin receptor. FEBS Lett 1982; 145:245–249. 7. Russo D, Chazenbalk GD, Nagayama Y, Wadsworth HL, Seto P, Rapoport B. A new structural model for the thyrotropin (TSH) receptor as determined by covalent crosslinking of TSH to the recombinant receptor in intact cells: evidence for a single polipeptide chain. Mol Endocrinol 1992; 5:1607–1612. 8. Loosfet H, Pichon C, Jolivet A, Misrahi M, Caillou B, Jamous M, Vannier B, Milgrom E. Two subunit structure of the human thyrotropin receptor. Proc Natl Acad Sci USA 1992; 89: 3765–3769. 9. Chazenbalk GD, Tanaka K, Nagayama Y, Kakinuma A, Jaume JC, McLachlan SM, Rapoport B. Evidence that the thyrotropin receptor ectodomain contains not one, but two, cleavage sites. Endocrinology 1997; 138:2893–2899. 10. Nagayama Y, Wadsworth HL, Chazenbalk GD, Russo D, Seto P, Rapoport B. Thyrotropin– luteinizing hormone/chorionic gonadotropin receptor extracellular domain chimeras as probes for TSH receptor function. Proc Natl Acad Sci USA 1991; 88:902–905.

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11. Nagayama Y, Wadsworth HL, Russo D, Chazenbalk GD, Rapoport B. Binding domains of stimulatory and inhibitory thyrotropin (TSH) receptor autoantibodies determined with chimeric TSH-lutropin/chorionic gonadotropin receptors. J Clin Invest 1991; 88:336–340. 12. Matsuba T, Yamada M, Suzuki H, Kanai A, Isozaki O, Yoshida T, Tsushima T, Yasukawa K. Expression of recombinant human thyrotropin receptor in myeloma cells. J Biochem 1992; 118:265–270. 13. Chazenbalk GD, Kakinuma A, Jaume JC, McLachlan SM, Rapoport B. Evidence for negative cooperativity among human thyrotropin receptors overexpressed in mammalian cells. Endocrinology 1996; 137:4586–4591. 14. Minich WB, Behr M, Loos U. Expression of a functional tagged human thyrotropin receptor in HeLa cells using recombinant vaccinia virus. Exp Clin Endocrinol Diab 1997; 105:282– 290. 15. Costagliola S, Morgenthaler NG, Hoermann R, Badenhoop K, Struck J, Freitag D, Poertl S, Weglohner W, Hollidt JM, Quadbeck B, Dumont JE, Schumm-Draeger PM, Bergmann A, Mann K, Vassart G, Usadel KH. Second generation assay for thyrotropin receptor antibodies has superior diagnostic sensitivity for Graves’ disease. J Clin Endocrinol Metab 1999; 84:90– 97. 16. Takai O, Desai RK, Setharamaiah GS, Jones CA, Allaway GP, Akamizu T, Kohn LD, Prabhakar BS. Prokaryotic expression of the thyrotropin receptor and identification of an immunogenic region of the protein using synthetic peptides. Biochem Biophys Res Commun 1991; 179:319–326. 17. Harfst E, Johnstone AP, Nussey SS. Characterization of the extracellular region of the human thyrotropin receptor expressed as a recombinant protein. J Mol Endocrinol 1992; 9:227–236. 18. Huang GC, Collison KS, Mc Gregor AM, Banga JP. Expression of a human thyrotropin receptor fragment in Escherichia coli and its interaction with the hormone and autoantibodies from patients with Graves’ disease. J Mol Endocrinol 1992; 8:137–144. 19. Graves PN, Vlase H, Bobovnikova Y, Davies TF. Folding of the recombinant human thyrotropin receptor (TSH) extracellular domain: identification of folded monomeric and tetrameric complexes that bind TSHR autoantibodies. Endocrinology 1995; 136:521–527. 20. Costagliola S, Alcalde L, Ruf J, Vassart G, Ludgate M. Over-expression of the extracellular domain of the thyrotropin receptor in bacteria; production of thyrotropin-binding inhibiting immunoglobulin. J Mol Endocrinol 1994; 13:11–21. 21. Bobovnikova Y, Graves PN, Vlase H, Davies TF. Characterization of soluble, disulfide bondstabilized, prokaryotically expressed human thyrotropin receptor ectodomain. Endocrinology 1997; 138:588–593. 22. Morgenthaler NG, Tremble J, Huang G, Scherbaum WA, McGregor AM, Banga JP. Binding of antithyrotropin receptor autoantibodies in Graves’ disease serum to nascent, in vitro translated thyrotropin receptor: ability to map epitopes recognized by antibodies. J Clin Endocrinol Metab 1996; 81:700–706. 23. Prentice L, Sanders JF, Perez M, Kato R, Sawicki J, Oda Y, Jaskolski D, Furmaniak J, Smith BR. Thyrotropin (TSH) receptor autoantibodies do not appear to bind to the TSH receptor produced in an vitro transcription/translation system. J Clin Endocrinol Metab 1997; 82:1288– 1292. 24. Huang GC, Page MJ, Nicholson LB, Collison KS, McGregor AM, Banga JP. The thyrotropin hormone receptor of Graves’ disease: overexpression of the extracellular domain in insect cells using recombinant baculovirus expression system. J Mol Endocrinol 1993; 10:127–142. 25. Seetharamaiah GS, Desai RK, Dallas JS, Tahara K, Kohn LD, Prabhakar BS. Induction of TSH binding inhibitory immunoglobulins with the extracellular domain in insect cells using recombinant baculovirus expression system. Autoimmunity 1993; 14:315–320. 26. Seetharamaiah GS, Kurosky A, Desai RK, Dallas JS, Prabhakar BS. A recombinant extracellular domain of the thyrotropin (TSH) receptor binds TSH in the absence of membranes. Endocrinology 1994; 134:549–554.


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27. Fan J, Seetharamaiah GS GS, Desai RK, Dallas JS, Wagle NM, Prabhakar BS. Analysis of autoantibody reactivity in patients with Graves’ disease using recombinant extracellular domain of the human thyrotropin receptor and synthetic peptides. Autoimmunity 11993; 15:285– 291. 28. Vlase H, Matsuoka N, Graves PN, Magnusson RP, Davies TF. Folding-dependent binding of thyrotropin (TSH) and TSHR autoantibodies to the murine TSH receptor ectodomain. Endocrinology 1997; 138:1658–1666. 29. Seetharamaiah GS, Dallas JS, Patibandla SA, Thotakura NR, Prabhakar BS. Requirement of glycosylation of the human thyrotropin recptor ectodomain for its reactivity with autoantibodies in patients’ sera. J Immunol 1997; 15:2798–2804. 30. Chazenbalk GD, Rapoport B. Expression of the extracellular region of the thyrotropin receptor in baculovirus using a promoter active earlier than the polyhedrin promoter: implications for the expression of functional, highly glycosylated proteins. J Biol Chem 1995; 1995:1543– 1549. 31. Rapoport B, McLachlan SM, Kakinuma A, Chazenbalk GD. Critical relationship between autoantibody recognition and TSH receptor maturation as reflected in the acquisition of mature carbohydrate. J Clin Endocrinol Metab 1996; 81:2525–2533. 32. Harfst E, Johnstone AP, Nussey SS. Characterization of the extracellular region of the human thyrotrophin receptor expressed as a recombinant protein. J Mol Endocrinol 1992; 9:227–236. 33. Chazenbalk GD, Rapoport B. Cleavage of the thyrotropin receptor does not occur at a classical subtilisin-related proprotein covertase endoproteolytic site. J Biol Chem 1995; 269:32209– 32213. 34. Chazenbalk GD, Jaume JC, McLachlan SM, Rapoport B. Engineering the human thyrotropin receptor ectodomain from a non-secreted form to a secreted, highly immunoreactive glycoprotein that neutralizes autoantibodies in Graves’ patients sera. J Biol Chem 1997; 272:18959– 18965. 35. Chazenbalk GD, Wang Y, Guo J, Hutchison JS, Segal D, Jaume JC, McLachlan SM, Rapoport B. A mouse monoclonal antibody to a thyrotropin receptor ectodomain variant provides insight into exquisite antigenic conformational requirement, epitopes and in vivo concentration of human autoantibodies. J Clin Endocrinol Metab 1999; 84:702–710. 36. Chazenbalk GD, McLachlan SM, Pichurin P, Rapoport B. A prion-like shift between two conformational forms of a recombinant thyrotropin receptor A- subunit module: purification and stabilization using chemical chaperones of the form reactive with Graves’ autoantibodies. J Clin Endocrinol Metab 2001; 86:1287–1293. 37. Chazenbalk GD, Pichurin P, McLachlan SM, Rapoport B. A direct assay for thyrotropin receptor autoantibodies. Thyroid 1999; 9:1057–1061. 38. Bolton J, Sanders J, Oda Y, Chapman C, Konno R, Furmaniak J, Rees Smith B. Measurement of thyroid-stimulating hormone receptor autoantibodies by ELISA. Clin Chem 1999; 45:2285– 2287. 39. Osuga Y, Kudo M, Kaipia A, Kobilka B, Hsueh AJ. Derivation of functional antagonists using N-terminal extracellular domain of gonadotropin and thyrotropin receptors. Mol Endocrinol 1997; 11:1659–1668. 40. Osuga Y, Liang SG, Dallas JS, Wang C, Hsueh AJ. Soluble ectodomain mutant of thyrotropin (TSH) receptor incapable of binding TSH neutralizes the action of thyroid-stimulating antibodies from Graves’ patients. Endocrinology 1998; 139:671–676. 41. Da Costa CR, Johnstone JP. Production of the thyrotropin receptor extracellular domain as a glycosylphosphatidylinositol-anchored membrane protein and its interaction with thyrotroin and autoantibodies. J Biol Chem 1998; 273:11874–11880. 42. Costagliola S, Khoo D, Vassart G. Production of bioactive amino-terminal domain of the thyrotropin receptor via insertion in the plasma membrane by a glycosylphosphatidylinositol anchor. FEBS Letts 1998; 436:427–433.

Index

Acquired immunity, 47–48 Acropachy, phalangeal, 47–48, 102, 109, 223, 274, 285, 293, 295 Adenoma, thyroid, 107 Adhesion molecules, 85, 91–96 as costimulatory molecules, 92–94 classification of, 92–93 immunoglobulin supergene family (IGSF), 91–94, 96 integrins, 91–93 selectins, 91–93 expression of, 85, 94–95 ligands of, 91–94 regulation of expression, 94 Adipocyte differentiation, 217–218 Aging eyelids and brows, 425–428, 426 midface descent, 425, 426, 432 Anatomy, orbital (see Orbital anatomy) Antigen-presenting cells (APCs), 42–43, 52, 54, 55, 65–66, 80, 117, 118, 199– 200, 201, 203 autoantigen-presenting cells, 54 dendritic cells, 42–43, 54, 57–58 in immune response, 42–43 macrophages, 42, 54, 79 MHC-HLA and (see Major histocompatibility complex) Antigen-specific receptors, 51, 57 Antithyroid drugs (ATD), 103, 155, 156, 157–165, 171, 174–175, 177–180, 182, 185–186, 189–193, 244–248 adjunctive testing, 157

[Antithyroid drugs] adjunctive therapy, 161–163 agranulocytosis following, 157, 159 beta blockade, 161, 165 bile acid sequestrants, 163 dosing regimens, 157, 159, 160 fetal hypothyroidism following, 157 glucocorticoids, 162 in children, 163 in pregnancy, 164 indications for, 159 lithium, 162, 165 radioiodine, 164 rh granulocyte colony-stimulating factor (GCSF), 159 thionamides complications, 159 methimazole (MMI), 157–159, 158, 160, 163–164 in pregnancy, 164 propylthiouracil (PTU), 157–159, 158, 160–164 in children, 163 in pregnancy, 164 Apoptosis, 56–57, 67, 70 A-scan ultrasonography, 309–310, 312, 312– 315, 317 Autoimmune disease, 48, 51–61, 65–77, 80, 81–85, 113, 117, 118, 190, 285, 293, 295 adhesion molecules in, 91–96 animal models, 25, 79–82 autoimmune thyroiditis, 82 457

458 [Autoimmune disease] bullous pemphigoid, 84–85 Crohn’s disease, 82–83 cytokines in, 79–90 diabetes mellitus, 80, 83–85, 113, 117, 120, 120 experimental, 80 Graves’ disease, 97–106 (see also under Graves’ disease) Hashimoto’s thyroiditis, 117, 141, 223, 225–226, 228, 251–252, 286 inflammatory bowel disease, 80, 95 inflammatory mediators in, 65–77 MHC-HLA association in, 117 multiple sclerosis, 80, 80, 82–83, 110– 111, 119, 139–142, 226 myasthenia gravis (see Myasthenia gravis) p38 mitogen-activated protein kinase (p38 MAPK), 66–71, 71, 72 pemphigus vulgaris, 84 rheumatoid arthritis, 80, 82–85, 113, 120 Sjo¨gren’s syndrome, 84 stress proteins [heat-shock proteins (HSP)], 67, 71–74, 73 systemic lupus erythematosus, 80, 83 Toll-like receptors (TLR), 66–70, 74 Autoimmune encephalomyelitis, 80–82 Autoimmune thyroid disease, Hashimoto’s thyroiditis, 117, 141, 223, 225–226, 228, 251–252, 286 Thyroid eye disease (see Thyroid eye disease) Autoimmune thyroiditis, 82 Autoimmune uveitis, 81 Autoimmunity, 48–49, 79, 81, 86, 100, 102, 225 Basophils, 41 B cells, 43, 47, 66–67, 84 activation and proliferation of, 84 responses to inflammation mediated by, 66–67 tolerance in, 59–61, 60–61 Blepharoplasty for thyroid eye disease, 425– 434 brow ptosis, 426–428, 430, 432 complications of, 429–430, 432–433 dermatochalasis, 425, 426, 428 evaluation, 425, 427–432 eyelid laxity, 425, 426, 431–342, histological considerations, 425 midface decent, 425, 426, 432

Index [Blepharoplasty for thyroid eye disease] patient history, 427 preoperative evaluation, 425, 427, 431– 432 surgery, 428–431 Botulinum toxin for eyelid retraction, 407–413 pharmacology of, 408–409, 409 Branchial arches, 12 Branchial arteries, 12 Brow ptosis, 426–428, 430–432 B-scan ultrasonography, 309–311, 311, 313– 315, 317 Bullous pemphigoid, 84–85 Cancer, thyroid, 107, 191–193 CD40, expression by orbital fibroblasts, 216–217 Ceramide, 70 Collagen-induced arthritis, 80–81, 85 Collagen synthesis, 201, 202–204 Compressive optic neuropathy (see Optic neuropathy, compressive) Computed tomography (CT), 218, 301–306, 380–381, 386, 436 axial and coronal images in, 302–303 findings in optic neuropathy, 330–332, 331–332 findings in thyroid eye disease, 301–306, 308 multiplanar reconstruction, 302 soft tissue and bone windows in, 301 Cornea decompensation after blepharoplasty, 429 examination of, in Graves’ disease, 427 pathology of, in Graves’ disease, 280 Costimulatory molecules, 52, 54–55, 57–58, 65–66 Crohn’s disease, 82–83, 293 CT (see Computed tomography) Cyclotorsion, 391, 397 excyclotorsion, 391 incyclotorsion, 397 Cytokines, 52, 58, 59, 66, 69–70, 72, 79–95, 80, 91–92, 94, 199–200, 201, 202 in animal models, 79–82 in autoimmune disease, 79–90 in thyroid eye disease, 85–86 interferon (IFN)-γ, 79, 80, 81, 83, 94–95 interleukin (IL)-1 (IL-1), 92, 94 IL-4, 79, 81, 84–85, 80, 94, 120 IL-6, 94

Index [Cytokines] IL-10, 79, 80, 81–85 IL-12, 79, 80, 81–83 IL-13, 84–85 IL-18, 79 Transforming growth factor (TGF)-β, 79 Tumor necrosis factor (TNF)-α, 80, 81– 82, 93–95 Cytotoxic T-lymphocyte-associated-4 gene, 117–119, 118, 121 Decompression, orbital, 2, 262, 263, 266, 268, 305–306, 322, 324, 357–377, 379–388, 373, 391 Dendritic cells, 42–43 Dermatochalasis, 425, 426, 428 Dermopathy, Graves’-associated, 102, 107, 110, 113, 127, 275, 285, 293, 295 Diabetes mellitis, 80, 95, 113, 117, 120, 120, 127, 293 Diagnostic ultrasound, 309–317 (see also Ultrasonography in thyroid eye disease) Diplopia, 2, 139, 340–341, 335, 338, 340– 341, 389–405, 394, 411–412 (see also Strabismus) chemodenervation for, 398 conservative treatment of, 397–398 euthyroidism and, 389, 398 eyelid retraction and, 389, 402, 402 following orbital decompression, 373, 391, 398 medical therapy, 340–341, 389–405 surgical therapy, 391, 398–402 Dry eye syndrome, 338–339 Environmental factors in Graves’ disease, 114, 127–138 Eponyms, for Graves’ disease, 3–8 Eosinophils, 42 Episcleral venous pressure, 379–320 Epitopes, 51–55, 58 Esotropia, 391, 394, 395 Euthyroid eye disease, 102, 103, 389, 398 Excyclotorsion, 391, 397, 400–401 Exophthalmic goiter (see Goiter) External beam irradiation (see Radiation therapy for thyroid eye disease) Exophthalmos, 1–2, 97, 174, 223, 285–286, 293, 295, 358, 393 Exotropia, A-pattern, 391, 394, 399–400

459 Extraocular muscles, 25, 48, 218, 223–224, 228, 265–270, 285–286, 302, 389– 405 (see also specific eye muscles) autoantibodies, 223–233 autoantigens, 224–231 computed tomography of, 218, 302–303, 307, 330–332, 331, 332 magnetic resonance imaging of, 218, 331– 332 ultrasonography of, 309–315, 330 fatty infiltration of, 218 pathology in Graves’ disease, 276–278, 277, 303 strabismus, 389–405 surgery on, 398–402 Eye muscle autoantibodies, 223–233 Eye muscle autoantigens, 224–231 cytotoxic antibodies, 228 flavoprotein (Fp), 225–226, 227, 229, 229–230, 230–231 55 kDa (G2s) protein, 224, 226–229, 229–230, 230 64 kDa protein, 224–226 Eyebrow brow ptosis, 428 evaluation, 428 fat pads, thickened, 426, 427–428, 430, 432 Eyelid aging changes, 425–428 anatomy, 415, 431 blepharoplasty, 428–434 complications, 429–430, 432–433 evaluation, 425, 427–429, 431–432 surgery, 428–431 dermatochalasis, 425, 426, 428 edema, 425–426, 426, 428, 429 evaluation of, 425, 427–432 Hering’s law, 415 histology in Graves’ disease, 425 in Graves’ disease, 407–408, 415–423, 416 lag, 285 laxity, 425, 431–432 malposition, caused by proptosis, 427 margin position, 428 midfacial ptosis and, 426, 432 normal position of, 415, 428 pathophysiology in Graves’ disease, 407– 408 proptosis and, 432 ptosis of, 425, 428, 396, 396

460 [Eyelid] retraction of (see Eyelid retraction) scleral show, 431 Eyelid retraction, 1, 285, 335, 340, 389, 402, 407–413, 415–422, 426, 427, 428, 431 botulinum toxin, 407–413 complications of, 408 differential diagnosis, 408 levator aponeurosis recession, 417–421, 418–420, 428–431 lateral tarsorrhaphy, 417 medical treatment, 407–413, 417 retractor recession, 418, 421–422, 421– 422, 432–433, 432–433 surgical correction, 415–422 Fat, orbital, 215–222 adipocyte differentiation, 217–218 connective tissue subpopulations, 217 cytokine susceptibility, 216 expression of TSH receptor, 218–219 Fibroblasts, preadipocyte, 208, 211, 217–218 Fibroblasts, retro-orbital, 201, 202–203, 207–213, 210, 210–219, 224 Gene expression, 67, 69 Gestational transient thyrotoxicosis, 148 Glaucoma in thyroid eye disease, 319–326, 321 clinical examination for, 321–322 mechanisms of, 319–320 episcleral venous pressure, 319–320, 322–323 inferior rectus muscle, fibrosis, 319 mucopolysaccharide deposition, 320, 324 orbital congestion, 319–320 medical management of, 322–324 alpha-adrenergic blockers, 323 beta-adrenergic blockers, 323 carbonic anhydrase inhibitors, 323 surgical management of, 323–324 cyclophotocoagulation, 323 filtration surgery, 323 laser trabeculoplasty, 323 orbit, decompression of, 322, 324 Glycoprotein hormone receptors, 20 follitropin receptor (FSHR), 20 lutropin receptor (LHR), 20 thyroid-stimulating hormone receptor (TSHR), 20

Index Glycosaminoglycans (GAG), 235–241 deposition of, 1, 201, 201, 203–204, 275– 276, 278–279 in Graves’ orbitopathy, 235–241 in orbital tissue, 236–239, 238–239, 273 Goiter, 1, 3, 6, 25, 101–103, 107–108, 113, 127, 131, 165, 174, 177–179, 191– 193, 207, 274 exophthalmic, 1 experimental induction of, in mice, 25 fetal, 103, 164 in Graves’ disease, 207 in pregnancy, 144, 146 nontoxic, 95 toxic multinodular, 97, 102, 107, 131, 145 (see also Plummer’s disease) Graves, Robert James, 5, 97, 199 Graves’ disease (GD) (see also under specific headings) cancers associated with, 191–193 children and, 189–190 clinical features, 100–101, 107–111, 285– 299, 292 dermopathy and (see Pretibial myxedema) differential diagnosis of, 186 endogenous sex hormones and, 128 environmental factors in, 114, 127–138 drug usage, 128, 134 infection, 114, 128, 134 intrauterine environment, 134 iodine intake, 114, 128, 129–130, 134– 135 smoking, 119, 128, 129, 131–132, 135, 251–259 stress, 114, 128, 129, 131–133, 135 eponyms for, 3–8 extrathyroidal manifestations of, 107–111, 199–203, 215–218, 223, 251–259, 285–295 acropachy, phalangeal, 47–48, 102, 109, 223, 274, 285, 293, 295 Graves’-associated dermopathy (see Pretibial myxedema) Graves’-associated orbitopathy (see Thyroid eye disease) eye manifestations (see Thyroid eye disease) gender preponderance, 139–140 genetic disposition to organ autoimmunity in, 139 genetics of, 113–125, 128–130 candidate genes, 120

Index [Graves’ disease (GD)] cytotoxic T-lymphocyte-associated-4 (CTLA-4) gene, 117–119, 118, 119, 121, 128 familial clustering, 113–114, 117–118, 120 GD-1 gene region, 117, 120, 128 GD-2 gene region, 120–121, 128 GD-3 gene region, 120–121, 128 MHC-HLA region, 115–117, 119, 128 MNG (multinodular goiter)-1 gene region, 119–120 twin studies, 114, 121, 128, 132, 135 histopathology, 274–275 incidence of, 97, 130 infection and, 114, 128, 134 laboratory evaluation of, 29–39, 171, 177–178, 181 malignancy and, 191–193, 293 medical therapy, 155–165 myasthenia gravis and, 80, 83, 110–111, 119, 139–142, 140, 226 neonatal, 36 orbitopathy and (see Thyroid eye disease) overview of, 97–106 pediatric, 163–164 predisposition to, 98–100 pregnancy, and, 143–153, 189 pretibial myxedema (dermopathy) and, 107, 109, 127, 223, 275, 285, 293, 295 prevalence of, 130 racial preponderance, 139 radioactive iodine assay for, 35 sex hormones and, 128 signs and symptoms of, 97–106, 108–111, 185, 189–190 smoking and, 80, 99, 103, 119, 128, 129, 131–132, 135, 251–259 stress and, 114, 128, 129, 131–133, 135 systemic manifestations of, 100–101, 107–111 thyroid function tests, 29–39, 34, 171, 177–178, 181 treatment of, 155–169 antithyroid drug administration, 155– 169, 171, 174–175, 177–180, 182, 185–187, 189–193, 244–248 radioactive iodine therapy, 171–186, 189–193, 243–248 surgery, 171, 174, 177, 180–182, 185– 193, 244–245, 248

461 Graves’ ophthalmopathy (see Thyroid eye disease) Graves’ orbital disease (see Thyroid eye disease) Graves’ orbitopathy (see Thyroid eye disease) Graves’ thyrotoxicosis, 109 (see also Thyrotoxicosis) Growth factor-β, transforming (TGF-β), 79 Hashimoto’s thyroiditis, 117, 141, 223, 225– 226, 228, 251–252, 286 Heat-shock proteins (HSP), 67, 71–74, 73, 85, 203 Histopathology of systemic Graves’ disease, 273–275 bone, 274 heart, 274 lymph nodes, 274 skeletal muscles, 274–275 skin, 275 thymus gland, 274 thyroid gland, 274 Histopathology of thyroid eye disease, 276– 280 adipose tissue, 278–279 cornea, 280 extraocular muscles, 276–278 eyelid skin, 425 lacrimal gland, 279–280 optic nerve, 280 orbital connective tissue, 278–279 Human chorionic gonadotrophin (hCG), 98, 144–145, 148 Human leukocyte antigen (HLA) expression of, 134 HLA system, 115–117, 115, 119, 121, 134 Hyperthyroidism, 97–101, 107–111, 127, 134, 155, 159, 207–208, 243 (see also Graves’ disease) causes of, drug induced, 130, 134 experimental induction of, 25 factitious, 107 Graves’ disease, 145–146 hormone over-replacement, 145 hydatidiform mole, 145, 149 hyperemesis gravidarum, 145, 148–149 iatrogenic, 107 iodine induced, 107, 130 lithium use and, 134, 163

462 [Hyperthyroidism] neonatal, 36 subacute thyroiditis, 145 toxic adenoma, 145 toxic multinodular goiter, 145 TSH hypersecretion, 145 experimental, 25, 107 fetal, 147, 189 laboratory tests for, 29–39, 171, 177–178, 191 neonatal, 36 pregnancy and, 143–153, 189 radioactive iodide therapy for, 171, 174– 175, 177–180, 244–248 recurrent, 155, 157, 159, 191–193 surgery for, 9–18, 185–193 (see also Thyroidectomy) systemic manifestations, 100–101, 107– 111 cardiovascular, 111 gastrointestinal, 111 lipid metabolism, 111 muscle, 109, 111 reproductive, 111 respiratory, 111 surgery for, 177, 180–181 symptoms and signs of, 97–106, 108–111, 185, 189–190 transient, 149 Hyperthyroxinemia, 109 Hypertropia, 391–392 Hypokalemic periodic paralysis, 108, 111 Hypoparathyroidism, following thyroidectomy, 10 Hypothyroidism, 3, 6, 25, 100–104, 192, 286 after therapy, 245–248 after thyroidectomy, 187–189 autoimmune, 102 in children, 190 fetal, 103 following antithyroid drugs, 157, 164 following 131I administration, 177–178, 18, 245–248 in pregnancy, 144–145 lithium use and, 163 postpartum, 149 Hypotropia, 391, 392, 392–393, 396, 399 Immune self-tolerance, 48, 51–63 Immune system, 41–50, 58 Immunity acquired (adaptive), 41–42

Index [Immunity] afferent phase, 42 cell-mediated, 46 effector phase, 42, 47–48 humoral, 42, 46 innate, 41–42 Immunocompetence, 54, 54 Immunoglobulins, 43–44, 44 Immunological mechanisms, in thyroid eye disease, 199–206 Immunosuppression in the treatment of thyroid eye disease, 2, 341–344, 436– 437 glucocorticoids, 341–344 indications and contraindications, 341–344 nonsteroid immunosuppressants, 343–344 plasmapheresis, 344 side effects of, 342–343, 343 somatostatin, 435–442 Incyclotorsion, 397 Infection, as a cause of Graves’ disease, 114, 128, 134 Inferior constrictor muscle, 13 Inferior oblique muscle, 391, 394 Inferior parathyroid gland, 11, 15 Inferior rectus muscle (see also Extraocular muscles; Strabismus) fibrosis of, 319 imaging of, 302–303, 307 paresis of, 392 recession of, 392–394, 399, 402 restriction of, 391, 392, 400 Inflammatory bowel disease, 80, 95 Inflammatory mediators, 65–77 gene expression, 67, 69 Interferon-γ (INF-γ), 79, 80, 81, 83, 94–95 Interleukin (IL), 79, 80, 81, 84–85, 92, 94 associated kinase, 67 IL-1, 92, 94 IL-4, 79, 81, 84–85, 80, 120 IL-6, 94 IL-10, 79, 80, 81–85 IL-12, 79, 80, 81–83 IL-13, 84–85 IL-18, 79 receptor, 67 Intraocular pressure, 319–320, 320, 322, 323, 337 Iodine clearance in pregnancy, 144 dietary intake of, 102–103, 114, 128, 129–130, 134–135, 159

Index [Iodine] as a cause of Graves’ disease, 128, 129–130, 134–135 postpartum uptake of, 149 stable iodine, 161, 165 uptake, 155 131 Iodine, 171–184 (see Radioactive iodine) Isotope imaging, 175 Laboratory tests for hyperthyroidism, 29–39, 171, 177–178, 181 Lacrimal gland imaging, 303 evaluation in blepharoplasty, 428 pathology in Graves’ disease, 279–280 preservation of ductules, 430 Lagophthalmos, 285, 427, 429, 430 Lateral rectus muscle (see also Extraocular muscles; Strabismus) imaging of, 302–303, 307 paresis of, 391, 394 Lid lag, 285 Ligands, 65–66 Long-acting thyroid stimulator (LATS), 98 Lymphocytes, 41–53, 57, 79 and self-tolerance, 51–61 apoptosis and, 57 in mediating orbital disease, 199–203 in the immune responses, 42–43 B lymphocytes, 43, 47, 66–67, 84 natural killer cells, 43 T lymphocytes, 43, 47 stages of development, 52–53 Macrophages, 42, 79 Magnetic resonance imaging in thyroid eye disease, 218, 306–308, 331–332, 436 Major histocompatibility complex (MHC), 45–47, 53–54, 57–58, 65, 79, 80, 85, 100, 115–117, 118, 119, 200, 202–203 class I, 46–47, 85, 115 class II, 46–47, 47, 79, 115–116 class III, 115 MAPK (p38) pathway, 66, 72 Mast cells, 42 Medial rectus muscle, 303 (see also Extraocular muscles; Strabismus) imaging of, 302, 304, 307 recession of, 399 restriction of, 391, 394, 400

463 Merseburg triad, 3, 6 MHC-HLA (see Major histocompatibility complex) Mitogen-activated protein kinase pathway (p38 MAPK pathway), 66–71 Monocytes, 42 Mononuclear cell, 82, 84–85 MRI (see Magnetic resonance imaging) Multiple sclerosis, 119 Mutations, 25–26 Myasthenia gravis, 80, 83, 110–111, 119, 139–142, 140, 226, 293, 295 Myxedema (dermopathy), 113, 127, 223, 275, 285, 293, 295 (see also Pretibial myxedema) Neutrophils, 42 NF-κB, activation of, by TLRs, 67 Ocular hypertension (see Glaucoma) Oncholysis, 109, 109 Ophthalmopathy (eye disease) (see Thyroid eye disease) Ophthalmoplegia, 139 Optic disk, in optic neuropathy, 328–330 Optic disk edema, 329, 333 Optic nerve, 265, 268–269, 280, 322, 328, 333 compression of, 280, 285, 305, 307, 327– 334 computed tomography (CT) of bilateral compression, 305 in Graves’ ophthalmopathy, 336–338, 341 mechanisms of, 330 surgery for, 332–333 visual field in, 327–328, 328 computed tomography (CT) of, 303, 305, 308 comparing optic nerve to rectus muscles, 304 examination of, 322 magnetic resonance (MR) image of, caused by enlargement of the rectus muscles, 307 pathology of, in Graves’ orbital disease, 280 Optic neuropathy, compressive, 1–2, 265, 268, 280, 285–286, 295, 305, 307, 322, 327–338, 341 clinical findings, 327–328 examination, 322 histopathology, 280

464 [Optic neuropathy, compressive] imaging, 304–305, 307–308, 330–332, 331, 332 pathogenesis, 330–331 therapy for, drug therapy, 332, 336–338, 341 radiation therapy, 332–333, 347–356 surgical decompression, 332–333, 357– 377, 379–388 ultrasound, 315–316, 330 visual field loss, 327–328, 328 visual testing, 328–330, 328 Orbicularis muscle, in aging, 425 Orbit anatomy of, 261–271, 262, 360, 360–363 clinical manifestations in thyroid eye disease, 285–295 computerized tomographic scan of, 301– 306, 330–332, 331, 332 congestion of, 319–320 decompression of, 262, 322, 324, 357– 377, 358, 379–388 external beam irradiation of, 347–356 fat of, 215–221 fibroblasts of, 207–211 histopathology, 273–283 inflammation of, 2, 303 magnetic resonance imaging of, 307–308, 331–332 staging of disease, 358, 359, 360 ultrasound, 309–317 videoendoscope in, use of, 371 Orbital anatomy, 261–271, 262, 360, 360– 363 arterial supply, 268–270, 269 connective tissue systems, 264–265, 264 decompression surgery and, 262–263, 266, 268, 360–363, 382 motor nerves, 267–268, 266–267 muscles of ocular motility, 265–267, 266, 268–270 osteology, 261–264, 262 sensory nerves, 268–269 (see also Optic nerve) venous drainage, 270, 271 Orbital decompression, 2, 259, 262–263, 266, 268, 305–306, 322, 324, 357– 377, 379–388, 391 bone decompression, 357–377 complications of, 372–374, 386 fat decompression, 366–367, 374, 379– 388, 385

Index [Orbital decompression] glaucoma and, 322, 324 imaging in, 305–306, 362–368, 380–381 indications for, 357–358, 373–375, 380– 381, 387 Orbital fat aging, in, 425 ballottement to assess, 429, 430, 432 computed tomography in, 302–303, 380– 381, 380 decompression of, 366–367, 374, 379– 388, 385 expansion of, in autoimmune response, 48 imaging of, 302–303, 306 increased, 48, 425, 426, 427, 428 magnetic resonance imaging in, 303, 380– 381 prolapse of, 425, 428 in thyroid eye disease, 215–221 Orbital fibroblasts, 201, 202–203, 207–213, 210–211, 216–219, 224 adipocyte differentiation of, 217–218 connective tissue subpopulations, 217 expression of CD40, 216–217 expression of thyroid-stimulating hormone receptor (TSHR), 218–219 in Graves’ orbital disease, 207–213, 210 stimulation of, 224 susceptibility to proinflammatory cytokines, 216 Orbital septum, weakening of, 425 Orbital veins anatomy, 270–271 imaging of, 303, 305, 307 superior ophthalmic vein. 303, 305, 307 Osteoporosis, 127, 274

p38-mitogen-activated protein kinase (p38 MAPK) pathway, 66–71 Paget’s disease, 293 Parathyroid gland, 10–11, 13, 14, 15, 16 Parry, Caleb Hillier, 3, 97 Parry’s disease, 3 Pemphigus vulgaris, 84 Pentoxifylline (Ptx), 443–449 effect on GAG synthesis, 444 effect on HLA-DR induction, 444–445 effect on retrobulbar fibroblasts, 444–445 immunomodulating effects of, 443–444 in the management of Graves’ orbital disease, 443–449

Index [Pentoxifylline (Ptx)] observations on eye symptoms, 445–447, 446-447 Peripheral blood mononuclear cells (PBMC), 82, 84–85 Phalangeal acropachy, 47–48, 102, 109, 223, 274, 285, 293, 295 Pituitary adenoma, 293 Plummer’s disease, 131 Postpartum thyroiditis, 148–149 Preadipocyte fibroblasts, 208, 211, 217–218 Pregnancy, in Graves’ disease, 143–153, 189 diagnosis and laboratory assessment, 146 estrogens in, 143 gestational transient thyrotoxicosis, 148– 149 goiter in, 144 human chorionic gonadotropin (HCG), 144–145, 145 hyperthyoroidism and, 145–150 iodine clearance in, 144 postpartum thyroid disease, 149 regulation of thyroid function during, 143–145, 150 spontaneous miscarriage, 146–148, 148, 150 thyroglobulin in, 144 thyroid antibodies and spontaneous miscarriage, 147–148 thyroid hormones in, 143–145 thyroid-stimulating hormone (TSH), 144, 145, 147, 150 T2, 144 T3, 143–144, 146, 147, 148, 150 T4, 143–144, 146, 147, 148, 150 thyroid-related changes during pregnancy, 147 thyroxine-binding globulin (TBG), 143– 144, 146, 147 Pretibial myxedema (dermopathy), 102, 107, 109, 110, 127, 275, 285, 293, 295 Proptosis, 2 (see also Exophthalmos) Ptosis, eyelid, 396, 396, 425, 428 Radiation safety, 178, 178 Radiation therapy for thyroid eye disease, 2, 347–356 mechanism of action of, 347–349, 355 apoptosis, 348, 349 clonogenic cell death, 348, 348 prospective randomized trials of, 347, 354–355

465 [Radiation therapy for thyroid eye disease] retrospective trial results of, 347, 351– 353, 355 technique for administration of, 347, 349– 351, 355 half-beam block technique for, 350, 350 isodose plan, 351, 351-352 types, 347, 349, 355 cobalt, 349 linear accelerator, 349 Radioactive iodine (131I), 171, 174–175, 177–180, 244–248 isotope imaging, 174 therapy for Graves’ disease, 2, 35–36, 103, 171–184 complications of, 177–179, 243–249 dialysis and, 181 dosage, 175–178, 176, 181 failure, 178 in children, 178 in nursing women, 178 in patients on dialysis, 181 in pregnant women, 178 indications and contraindications for, 174, 180 malignant change in the thyroid after, 174, 176–177 risks for orbital disease following, 243– 247 uptake (RAIU), 30, 35–36, 174–175, 177–178, 181 Radioimmunoassay (RIA), 30, 32, 34–35, 108 for measurement of TT4, 33 for measurement of free T3, 34 for measurement of TT3, 35 Rectus muscles (see also specific eye muscles) anatomy, 265–270 computed tomography, 303–304, 304, 393 fibrosis, 319 histopathology, 276–278 magnetic resonance imaging, 303 paresis, 39, 392 recession, 392–394, 399, 402 restriction, 391–393, 392, 394, 406 strabismus, 223–231 Recurrent laryngeal nerves, 10, 12, 13, 14, 16 Retraction, eyelid, 1–2, 285, 340, 398, 402, 407–413, 411–412, 415–422, 418–422, 425–429, 431 (see also Eyelid retraction)

466 Rheumatoid arthritis, 113, 120, 127 Rhytids, from aging, 425, 426 Self-tolerance, 48, 51–63, 80, 200 Sex hormones and Graves’ disease, 128 Sjo¨gren’s syndrome, 84 Smoking and thyroid eye disease, 99, 103, 119, 128, 129, 131–132, 135, 180, 251–259, 339 ethnic factors, 253–254 genetic factors, 254 mechanisms of action, 255–256 prevalence, 252–254, 253 Somatostatin and thyroid eye disease, 435– 442 clinical use of, 437–438 mechanisms of, 439–440 prevalence, 252–253 receptors, 437 Spontaneous miscarriage and thyroid disease, 147–148 Strabismus in thyroid eye disease, 285, 373, 389–405 chemodenervation in, 398 conservative treatment for, 397–398 differential diagnosis of, 390 esotropia, 391, 394, 395 euthyroidism, 389, 398 exotropia, A-pattern, 391, 394, 399 hyperthyroidism and, 389, 398 hypertropia, 391–392 hypothyroidism and, 389, 398 hypotropia, 391, 392, 392–393, 396, 399 measurement of, 397 patterns of, 391–396 proptosis in, 389, 390, 393–394, 397 ptosis, 396, 396 radiotherapy and, 391 surgery for, 391, 398–402 vertical, 393 Stress in Graves’ disease, 114, 128, 129, 131–133, 135 Stress proteins [heat-shock proteins (HSP)], 71–74, 73, 85, 203 Struma ovarii, 107 Superior limbic keratoconjunctivitis (SLK), 294, 339 Superior oblique muscle, 392 Superior ophthalmic vein, 303, 305, 307 Superior parathyroid gland, 11 Superior rectus muscle, 303 imaging, 302–303, 307

Index [Superior rectus muscle] increased volume of, 393 paresis of, 391 restriction of, 391, 392–393 Surgical anatomy in decompression surgery, 360–363 of the orbit, 261–271 of the thyroid gland, 9–18, 11, 13, 15 Systemic lupus erythematosus, 80, 83 T cells, activation of, 56–57, 65–66, 199–200, 201, 202–203 apoptosis and, 55–57 CD4⫹ T cells (T helper), 45, 47, 79 CD8⫹ T cells (T suppressor), 45, 47 helper T cells, 58–60 Th1, 45, 48, 58, 59, 79–86, 80 Th2, 45, 48, 58, 59, 79–86, 80 Th3, 79, 80 T-cell-dependent suppression, 58–59 T-cell receptor (TCR), 53–54, 65 down regulation of, 117, 118 in immunity, 44–45, 45 TCR complexes, 65–66 T-cell subsets, 80 CD4 T cells, 79 Th1 cells, 79–86, 80 Th2 cells, 79–86, 80 Th3 cells, 79, 80 Tr1 cells, 79, 80 receptor, 44–45, 45, 65–66, 69, 117, 118 receptor antibodies, 99–100 Technetium pertechnetate 99 (Tc99), uptake by thyroid gland, 102 Tetraiodothyronine (T4) (see Thyroxine) Thionamide, 102–103 Thymocytes, development of, 55 Thymus gland, 11, 53–54, 56, 58 enlargement of, 274 extrathymic tolerance, 54 intrathymic tolerance, 53–54, 58 thymocyte development, 55 Thyroglobulin (TG), 19, 100–101, 144, 149 Thyroglossal duct cysts, 10 Thyroid-associated lymphoid tissue (TALT), 200, 202 Thyroid-associated ophthalmopathy (TAO) (see Thyroid eye disease) Thyroid-associated phalangeal acropachy, 102, 109, 223, 274, 285, 293, 295 Thyroid-binding globulin (TBG), 33

Index Thyroid cancer, 107, 191–193 Thyroid eye disease (TED), 1, 2, 98–99, 101–103, 107–108, 113, 119, 127, 131–132, 139, 141, 146, 165, 171, 174, 177–182, 186, 190–193, 199– 213, 201, 215–233, 243–249, 244, 251–259, 273–283, 285–299, 301–306, 308–317, 319–356, 358, 379–405, 407, 417–423, 435–443 (see also under specific headings) clinical examination, 2, 335–338, 436 clinical findings, 215, 285–295 clinical manifestations of, 285–299, 292 computed tomography (CT) in, 301–305 cytokines in, 85–86, 199–200, 201, 202 decompression, orbital, 357–376, 379– 388 diabetes and, 327 diagnosis, 2, 286 diplopia in, 139, 389–405 eponyms for, 3–8 exophthalmos (proptosis), 285–286, 293, 295 eye muscle autoantibodies, 223–233 eyelid retraction, 285–286, 407–413, 415–422 following radioactive iodine, 243–249, 244–245 glaucoma in, 319–326, 321 glycosaminoglycans in, 235–241 histopathology, 223–224, 273–283 imaging in, 2, 301–308 immunological mechanisms of, 199– 206 magnetic resonance imaging (MRI) in, 306–308 management of, 319–455 blepharoplasty, 425–433 decompression, 357–377, 379–388 medical treatment, 335–346 radiotherapy, 347–356 optic neuropathy, 285–286, 328–333 orbital fat in, 215–221 overview of, 199–203 pathogenesis, 435–436 physical examination, 336–337 radioactive iodine and, 180–182, 243–249 radiation therapy for, 347–356 scintigraphy in, 437 signs and symptoms, 201, 286–293, 335– 336, 435–436 smoking and, 2, 119, 245, 247, 251–259

467 [Thyroid eye disease (TED)] strabismus in, 285, 389–405 ultrasound, 309–317 Thyroid function, 143–145 during pregnancy, regulation of 143–145, 147–149 postsurgical, 188 tests for, 29–39, 34, 171, 177–178, 181 Thyroid function tests, 29–39, 171, 177– 178, 181 Thyroid gland biopsy of, 113 cancer of, 191–193 ectopic, 10 embryology of, 9–12 enlargement of (see Goiter) function tests, 29–39 iodine, uptake of, 29–30, 35–36 laboratory studies, 29–39 immunochemiluminometric assay (ICMA), 31–32 radioimmune assay (RIA), 30, 32, 34– 36 thyroid-stimulating hormone (TSH), 29–35, 171, 178 thyroid-stimulating immunoglobulin (TSI), 29, 35–36 thyroxine (T4), 30, 32–35, 171, 177– 178, 181 time-resolved immunofluorometric assay (TR-IFMA), 31 triiodothyroxine (T3), 30, 32–34, 36, 171 TSH binding globulin (TBG), 33 TSH binding inhibiting antibody, 35 TSH receptor antibody (TRab), 29, 35– 36 TSH receptor inhibiting immunoglobulin (TBII), 35–36 lymphocytic infiltration of, 113 recurrent laryngeal nerve, relation to, 13 radioactive iodine, 35, 171–184 surgical technique, 12–17 surgical anatomy of, 9–18, 11, 13, 15 superior parathyroid gland, relation to, 11 thyroidectomy, 185–193 Thyroid hormones biosynthesis of, by iodine, 129 levels following therapy, 245, 245–248 thyroxine, 30, 97, 101, 103, 107, 113, 143–144, 146, 147, 148, 150, 161– 162, 188

468 [Thyroid hormones] triiodothyroxine, 97, 101, 107–108, 143– 144, 146, 147, 148, 150, 161–162 Thyroid optic neuropathy (see Optic neuropathy, compressive) Thyroid peroxidase (TPO), 19, 100–101, 147, 149 Thyroid-stimulating hormone (TSH), 19, 29– 35, 31, 32, 48–49, 98, 107–108, 113, 144–145, 147, 150, 159, 162, 164, 185, 186, 188–191, 200, 208– 209, 435–436, 245, 248, 435–436 Thyroid-stimulating hormone receptor, (TSHR), 19–20, 24–25, 29–35, 97–98, 100–103, 107–108, 113, 115, 118, 120, 127, 128, 155, 180, 185, 188–191, 200, 201, 202–203, 207–213, 215, 218–219, 224, 228, 230, 246- 247, 451–457, 453–454 antibodies to, 24, 29, 35–36, 130–131, 147, 164, 185, 208, 246, 247 direct TSHR autoantibody assay, development of, 453, 455 engineering a soluble protein, 451–457, 453, 454 expression of, by orbital fibroblasts, 215, 218–219 expression of, by preadipocyte fibroblasts, 208–211 function, 21–23 functionality in orbital preadipocyte fibroblasts, 209–211 G-coupled receptor superfamily, 20 gene, 23–24, 120 measurement of, 24 mutation data base, 26 preadipocyte fibroblasts, 211 protein expression, 21 role in Graves’ disease, 451, 455 role in thyroid physiology, 451 structure of, 19–25, 20, 451, 455 thyroid eye disease and, 207–213, 210 thyroid-stimulating immunoglobulin (TSI), 24 Thyroidectomy, 16, 103, 147, 156, 161, 164–165, 171, 174, 180–182, 185– 193, 244–245, 247–248 advantages and disadvantages, 192–193 complications of, 10, 12, 15, 174, 177, 191–193 for Graves’ disease, 185–193 for nodular goiter, 188

Index [Thyroidectomy] in children, 163 in pregnancy, 164 postoperative complications, 10, 12, 15, 188, 191–192 postoperative follow-up, 188–189 preoperative preparation, 186–187 Thyroiditis, 102, 107, 117, 148, 164, 175, 181, 229–230 animal model, 117, 229–230 destructive autoimmune, 102 postpartum, 148 toxic radiation, 164 Thyrotoxicosis, 97–98, 107–109, 111, 113, 140, 140, 146, 148–149, 172–175, 180–181 after radioactive iodide (RAI) therapy, 180 causes of, 172–173 in children, 189–190 gestational transient, 148–149 in myasthenia gravis, 140, 140 neonatal, 102, 104, 113 in pregnant women, 164, 189 systemic manifestations of, 100–101 transient, 175, 181 treatment of, 155, 161–165, 174 Thyroxine, 31–35, 97, 101, 103, 107–108, 113, 143–144, 146, 148, 150, 161– 162, 245 biosynthesis, 129 excess production of, 107 laboratory tests, 31–34 levels after therapy, 245, 247–248 measurement of, 30–35 replacement of, 188 T lymphocyte (see T cells) Toll-like receptors (TLR), 66–70 in innate immune responses, 68, 74 ligand recognition by, 67 pathogen-associated molecular patterns (PAMP), 68 Toxic radiation thyroiditis, 164 Tracheoesophageal groove, 13, 16 Transforming growth factor-β (TGF-β), 79 Triiodothyroxine (T3), 30–35, 97, 101, 107– 108, 143–144, 146, 148, 150, 245 free T3, 30, 34 measurement of, 30, 32–34 resin uptake assay (T3RU), 30, 33–34, 34 total T3 (TT3), 30, 35 toxicosis, 30

Index Tumor necrosis factor (TNF)-β, 81–82, 80, 93–95, 120 Ulcerative colitis, 293 Ultrasonography for thyroid eye disease, 309–317 A-scan, 309–310, 312, 312–315, 317 B-scan, 309–311, 311, 313–315, 317 muscles in, evaluation of, 309–313, 311– 315 optic disk in, elevation of, 315–316 optic neuropathy and, 330

469 [Ultrasonography for thyroid eye disease] orbital blood vessels in, 314–315 orbital fat in, 313–314 retrobulbar optic nerve sheath, distention of, 315 Vagus nerve, 10, 12 Vision loss, 1 von Basedow, Karl Adolph, 6, 97 von Basedow’s disease 3, 6 Yersinia enterocolitica, 134

About the Editors

JONATHAN J. DUTTON is Director of the Atlantic Eye and Face Center, Cary, North Carolina, and Clinical Professor at the University of North Carolina at Chapel Hill. The author, coauthor, or editor of numerous professional publications, presentations, and five medical textbooks, he is a Fellow of the American Academy of Ophthalmology, the American Academy of Cosmetic Surgery, the American College of Surgeons, and the American Society of Ophthalmic Plastic and Reconstructive Surgery, among others. Dr. Dutton received the Ph.D. degree (1970) from Harvard University, Cambridge, Massachusetts, and the M.D. degree (1977) from Washington University, St. Louis, Missouri. He was Professor of Ophthalmology and Director of Ophthalmic Plastic Surgery and Ophthalmic Oncology at Duke University Medical Center from 1983 until 1999. BARRETT G. HAIK is Hamilton Professor and Chair of the Department of Ophthalmology, University of Tennessee, Memphis. The author, coauthor, or editor of numerous journal articles, book chapters, and books, he is a Fellow of the American College of Surgeons, the American Academy of Ophthalmology, and the New York Academy of Sciences and a member of the American Ophthalmological Society. Dr. Haik received the M.D. (1976) and M.S. degrees (1985) in anatomy from Louisiana State University Medical Center, New Orleans. He trained for ophthalmology at the Edward S. Harkness Eye Institute, New York, New York, and served on the faculty of Cornell University Medical School, New York, New York, and the Tulane University School of Medicine, New Orleans, Louisiana.

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