Onset age is associated with outcome of radioiodine therapy in Graves' disease.

Controversy remains regarding the optimal dose calculation with radioiodine therapy for patients with Graves' disease. Here, we focused our analysis on data concerning the patient's pretreatment background, an empirically set dose of radioiodine and the post-treatment thyroid function, and investigated those factors that affected the outcome. The subjects consisted of 38 patients diagnosed as having Graves' disease. All patients were hospitalized to undertake radioiodine therapy between 1989 and 1998 at our hospital. At the follow-up periods of 6-, 12-, and 36-months after therapy, we divided the patients into two groups: one group those who had hypothyroid function, and the other those who had normal or hyperthyroid function. At 6- and 12-months, 50% of the patients belonged to the hypothyroid function group, whereas at 36-months, 55% of them had hypothyroid function. Logistic regression analysis, with the objective variable being the post-treatment hypothyroidism after 12 months, revealed that the significant factor was the onset age. We suggested that the age at onset should be considered in patients with Graves' disease to determine the optional radioiodine dose for the therapy.