Thiamazole pretreatment lowers the 131 I activity needed to cure hyperthyroidism in patients with nodular goiter

Context: Relatively low radioiodine uptake (RAIU) represents a common obstacle for radioiodine (131I) therapy in patients with multinodular goiter complicated by hyperthyroidism. Objective: To evaluate whether thiamazole (MTZ) pretreatment can increase 131I therapeutic efficacy. Design and Setting: Twenty-two patients with multinodular goiter, subclinical hyperthyroidism, and RAIU < 50% were randomized to receive either a low-iodine diet (LID; n = 10) or MTZ 30 mg/d (n = 12) for 42 days. Thyroid function and 24-hour RAIU were measured before and after treatment. Thyroid volume was evaluated by either magnetic resonance imaging or single photon emission computed tomography. Results: Mean 24-hour RAIU increased significantly from 32 ± 10% to 63 ± 18% in the MTZ group (P < .001). Consequently, there was a 31% decrease in the calculated median therapeutic 131I activity after MTZ (P < .05). No significant changes in 24-hour RAIU were observed after diet. In the MTZ group, median serum TSH levels increased sign...