Why is radioactive iodine given to hyperthyroid patients?

Radioactive iodine is administered to hyperthyroid patients primarily to target and destroy overactive thyroid tissue, thus reducing the production of thyroid hormones. This therapy works by utilizing the property of iodine, which is preferentially absorbed by the thyroid gland. The radioactive form of iodine emits radiation that selectively destroys the hyperactive thyroid cells, leading to a decrease in levels of thyroid hormones such as thyroxine (T4) and triiodothyronine (T3).

By reducing hormone production, radioactive iodine helps alleviate the symptoms of hyperthyroidism, which can include weight loss, rapid heartbeat, anxiety, and heat intolerance. This treatment is effective and often results in a long-term solution for managing hyperthyroid conditions, making it a commonly chosen therapy for patients diagnosed with Graves' disease or toxic nodular goiter.

In contrast, the other options do not accurately reflect the purpose of administering radioactive iodine. For instance, increasing metabolism or energy levels contradicts the need to reduce excessive thyroid hormone activity, while relieving symptoms of anxiety is not the primary objective of this treatment.