Iodine organification defect following treatment of thyrotoxicosis with antithyroid drugs.

Two patients remained clinically euthyroid following treatment for thyrotoxicosis with antithyroid drugs in spite of persistently elevated thyroid radioiodine uptakes not suppressable by exogenous triiodothyronine. Perchlorate discharge tests showed a defect in the intrathyroidal organification of iodine. Circulating levels of thyroxine were normal. From our study of 105 patients treated for thyrotoxicosis with antithyroid drugs, apparent remission of thyrotoxicosis by this mechanism might occur in up to 2 percent of patients.