[Iodine excess and thyroid dysfunction].

Hypothyroidism or hyperthyroidism may develop during iodine excess. Hypothyroidism occurs mostly in newborns or in elderly patients with underlying autoimmune thyroiditis and is treated by substitutive doses of thyroxine. Hyperthyroidism is of two types. Type I develops in patients with pretoxic thyroid glands, the radioactive tracer uptake remains high. This type is treated with thionamides and potassium perchlorate, as well as, in some cases, by thyroidectomy or iodine 131. Type II develops in non pretoxic thyroid gland, and it evoluates spontaneously towards euthyroidism, in several months, despite continuation of iodine excess. It responds to glucocorticoid therapy.