A publication of the American Thyroid Association

Summaries for Patients from Clinical Thyroidology by Ernest Mazzaferri, MD MACP
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Abbreviations & Definitions

Graves’s disease This is the commonest cause of hyperthyroidism (overactive thyroid). It is characterized by goiter, exophthalmos (Graves’ ophthalmopathy) and hyperthyroidism that is mediated by an autoimmune antibody-mediated stimulation of the thyroid gland.

GO is Graves’ ophthalmopathy

The characteristic features of Graves’ eye disease are symptoms of inflammation of the eye tissues. The eyes are painful, red and watery and the covering of the eye is inflamed and swollen. The lids and tissues around the eyes are swollen. The eyeballs bulge out of their sockets, and because of eye muscle movement, the eyes may be unable to move normally and there may be blurred or double vision. On examination, the degree to which the eyes are pushed out of their sockets can be measured using an instrument called an "exophthalmometer."

CAS is the clinical activity score that provides a guide in the management of patients with Graves’ ophthalmopathy. The original description of CAS is found at:

What is the study about? Radioiodine therapy for hyperthyroidism may have an effect on the eye component of Graves’ disease.

The full article title: “Radioiodine therapy and Graves’ ophthalmopathy” It is in the June 2008 issue of the Journal of Nuclear Medicine (Volume 49, Issue 6, pages 923-30. The authors are JC Sisson, M Schipper, CC Nelson, JE Freitas, and BR Frueh. The abstract can be obtained from:

What is known about the problem being studied? The available randomized, controlled trials on the effects of radioiodine (131I) therapy on Graves’ ophthalmopathy (GO), which have been done mainly in Europe, show that about 15% of patients have new eye disease or progression of preexisting GO within 6 months after the administration of 131I.

What was the aim of the study? This study explores the effects, if any, on the of American patients with Graves’ disease treated with 131I

Who was studied? The study subjects were 76 patients with Graves’ disease, ranging in age from 10.6 to 72 years, of whom 61 (85%) were female. All had 131I therapy for Graves’ hyperthyroidism.

How was the study done? During follow-up evaluations at 2, 6, and 12 to 14 months after therapy, thyroid-function tests, thyroid stimulating hormone (TSH) measurements, and data from ophthalmologists and ophthalmic technicians were obtained to fulfill the 10 items of the clinical activity score (CAS), which is a standard means of evaluating the clinical degree of GO.

What were the results of the study? The mean exophthalmometer readings increased 2 mm or more but the changes were not statistically significant and spontaneously return to normal 1 year after 131I therapy.

How does this compare with other studies? The few randomized, prospective studies examining the potential impact of radioiodine therapy on GO found that approximately 15% of European patients have new eye disease or experience progression related to the treatment within 6 months. Still, the progression is mild and persists at 1 year in only 5%. The risk is greatest in patients with active GO treated with radioiodine and is almost eliminated by giving a short course of oral glucocorticoids and avoiding posttreatment hypothyroidism. Smokers are at increased risk of developing sever GO.

What are the Limitations of this study? This study has several important limitations. This is an unselected population and the study had an unusual use of the CAS system, grouping the patients results, rather than using individual observations, making it difficult to ascertain exactly how many of the patients had evidence of GO at baseline, and whether their disease was active.

What are the implications of this study? This study does not provide strong support for the notion that American patients do not develop Go after treatment with 131I. It is likely that the careful European studies of this subject provide information that is applicable to patients in the United States. (See below)

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