Final answer:
The radioactive iodine treatment for Graves disease uses Iodine-131 to destroy overactive thyroid tissue, thereby reducing hormone production and alleviating the condition.
Step-by-step explanation:
The mechanism of action of radioactive iodine in the treatment of Graves disease is to selectively target and progressively destroy the overactive thyroid tissue. Radioactive iodine, particularly Iodine-131 (I-131), is administered orally, and because the thyroid gland naturally absorbs iodine from the bloodstream, the radioactive iodine is taken up by the thyroid. The radioactive emissions from I-131 then damage the thyroid cells, which results in a reduction of the thyroid gland's activity and hormone production, thereby treating the symptoms of Graves disease.