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Glucocorticoid therapy does not alter the effect of radioactive iodine therapy in patients with hyperthyroidism caused by Graves’ disease

The background of the study. Patients with hyperthyroidism caused by Graves’ disease may have the onset or worsening of Graves’ eye disease when they are treated with radioactive iodine (I-131). Co-administration of a glucocorticoid reduces the likelihood of changes in the eyes. Whether it alters the antithyroid effect of I-131 was evaluated in this study.

How the study was done. The effect of I-131, with or without glucocorticoid therapy, on thyroid function was studied in 207 patients with hyperthyroidism caused by Graves’ disease. Ninety-six were treated with I-131 plus 25 mg of prednisolone daily for 30 days, and 111 were treated with I-131 alone. The reasons for adding prednisolone were mild-to-moderate Graves’ eye disease in 56 patients, smoking in combination with high serum thyrotropin (TSH)-receptor antibody values in 32, and both in 8. No patient treated with I-131 alone had eye disease, but 46 were smokers. The patients were evaluated at regular intervals for one year after I-131 therapy.

The results of the study. One year after I-131 therapy, approximately 35 percent of the patients in both groups had hypothyroidism, 25 percent had normal thyroid function, and 40 percent still had hyperthyroidism. Among the patients in the I-131-plus-prednisolone group, 57 percent had no change in their eyes, preexisting eye disease improved in 36 percent, and 7 percent had the onset or worsening of eye disease during the follow-up period. Among the patients in the I-131 alone group, 4 percent had onset of eye disease and 96 percent had no change in their eyes during follow-up.

The conclusions of the study. In patients with Graves’ hyperthyroidism, administration of prednisolone for 30 days starting when I-131 is given does not alter the long-term effect of I-131 therapy on thyroid function.

The original article. Jensen BE, Bonnema SJ, Hegedus L. Glucocorticoids do not influence the effect of radioiodine therapy in Graves’ disease. Eur J Endocrinol 2005;153:15-21.