Radiation-induced thyroiditis

Radiation-induced thyroiditis is a form of painful, acute inflammation of the thyroid gland that results from radioactive therapy used to treat hyperthyroidism, or from radiation delivered to treat head and neck cancer or lymphoma in the vicinity of the thyroid. The condition develops in approximately one percent of patients who receive radioactive iodine, also called I-131, therapy for Graves' disease, and it typically appears between five and ten days after the radioactive treatment is given, a distinctive timing window that helps distinguish it from other causes of thyroid pain in patients undergoing such treatment. It occurs because the rapid destruction of thyroid tissue by the radiation releases the hormones stored within that tissue, triiodothyronine and thyroxine, suddenly into the bloodstream; this surge triggers pain and tenderness in the thyroid region and can transiently worsen the very hyperthyroid symptoms the radioactive iodine treatment was meant to resolve, an ironic short-term consequence of an otherwise effective therapy.