Glucocorticoids do not influence the effect of radioiodine therapy in Graves'disease

Objective: We evaluated, in a retrospective study, whether glucocorticoids given in order to avoid initiation or aggravation of ophthalmopathy during radioiodine (I-131) therapy have an inadvertent effect on the final thyroid function. Methods: Consecutive patients with Graves' disease (median age 50 years, range 21-82 years) treated with I-131 therapy for the first time were included. Ninety-six patients (group 1) were given prednisolone (25 mg daily for 30 days beginning 2 days before I-131 therapy) because of present or previous mild ophthalmopathy or the presence of risk factors (tobacco smoking and high concentrations of TSH-receptor antibodies) for developing this complication. One hundred and eleven patients received I-131 therapy without prednisolone prophylaxis (group 2). Results: The patients in group I were younger than those in group 2 (44.6 +/- 12.0 years versus 51.3 +/- 15.1 years; P = 0.001). At 1 year post therapy the patients were classified as hypothyroid, euthyroid or hyperthyroid. In group 1, the numbers of patients were 23, 35 and 38, respectively, while the corresponding numbers in group 2 were 26, 40 and 45, respectively (P = 0.99 between groups). The cure rate (attainment of euthyroidism or hypothyroidism) was 60% in group I and 59% in group 2 (P = 0.97). No significant between-group difference was found, neither in the median time-interval until development of hypothyroidism nor until recurrence of the hyperthyroidism. Using logistic regression the cure rate correlated negatively with age (P = 0.041) and the size of the thyroid gland (P = 0.010) and positively with serum TSH at treatment (P = 0.034), whereas no significant impact was found for the use of prednisolone, gender, smoking, presence of anti-thyroid peroxidase antibodies, use of anti-thyroid drugs or the presence of eye symptoms. Conclusions: Although glucocorticoids in some contexts seem to attenuate the radiation-induced oxidative stress this had no impact on the final outcome following 1311 therapy of patients with Graves' disease.