Time course to hypothyroidism after fixed-dose radioablation therapy of Graves' disease in children

Objective: To characterize the development of hypothyroidism in pediatric patients who receive a fixed dose of radioactive iodine (RAI). Study design: Medical records of children treated with fixed-dose RAI for Graves' disease between 1993 and 2001 were reviewed. Multiple variables including sex, age, thyroid hormone levels, thyroid-stimulating immunoglobulin titer, antithyroid medication use, and 24-hour radioiodine uptake were investigated as possible predictive factors for the development of hypothyroidism after treatment. All patients received RAI at a dose of between 13.8 and 15.6 mCi (average, 14.7 mCi; SD, 0.5). Results: Permanent hypothyroidism developed in all 40 patients, although a second dose of RAI was required in one case. The average time to hypothyroidism was 77 days (SD, 32), with a range of 28 to 194 days; 75% of the patients were diagnosed with hypothyroidism between 40 and 90 days. RAI treatment was ineffective in an additional patient, who required subtotal thyroidectomy. Conclusions: We conclude that a fixed dose of RAI is effective therapy in nearly all pediatric patients with Graves' disease. Factors predicting the time course to hypothyroidism were not identified. (J Pediatr 2002;140:99-103).