[Hyperthyroidism due to excess iodine]

TWO TYPES: Hyperthyroidism may develop in around 10% of patients in excess iodine. It may reveal an undetected pretoxic thyroid disease (type I) or have been induced by excess iodine in previously normal thyroid gland or in an euthyroid goiter (type II). IODINE EXCESSE REVEALING THYROTOXICOSIS: In the former situation, symptoms appear shortly after the iodine load, thyroid scintigraphy shows significant uptake and therapy includes discontinuation of iodine excess, antithyroid drugs, potassium perchlorate and, if necessary, thyroidectomy or a therapeutic dose of iodide 131. IODINE-INDUCED THYROTOXICOSIS: In the latter situation (type II) hyperthyroidism may occur several years after the initiation of iodine excess, scintigraphy shows very low or no uptake, spontaneous remission is observed within six months, despite the persistence of iodine excess, and treatment is based on corticosteroids.