Five patients with iodine-induced hyperthyroidism.

Iodine-induced hyperthyroidism has been frequently described when iodine is introduced into an iodine-deficient area. However, it may also occur in patients with and without previous thyroid disease residing in iodine-sufficient areas. Five patients with iodine-induced hyperthyroidism seen in a 12-month period are described. All were exposed to iodine in the form of commonly used drugs (Betadine, Iodo-Niacin, amiodarone, and radiographic contrast dyes). The cause of iodine-induced hyperthyroidism is unclear, but it is probably more common in patients with goiters containing previously existing areas of autonomous function or iodine-poor thyroglobulin. Iodine-induced hyperthyroidism usually abates after iodine withdrawal in patients with multinodular goiters or normal thyroid glands. The hyperthyroidism is usually treated with beta-blockers and antithyroid thionamide drugs, although reinstitution of iodine to block thyroid hormone release or corticosteroids occasionally may be necessary. Iodine-containing drugs should be given with caution to patients with underlying thyroid disease.