What is a common long-term risk after radioactive iodine therapy for hyperthyroidism?

• A. Hypothyroidism requiring lifelong thyroid hormone replacement
• B. Persistent hyperthyroidism
• C. Thyroid cancer
• D. Hyponatremia

Answer: (A)

The main idea here is that radioactive iodine therapy for hyperthyroidism commonly leads to hypothyroidism in the long term. The radioactive iodine damages thyroid tissue over time, and as functional thyroid cells are lost, thyroid hormone production drops. When T4 and T3 fall, the pituitary sends more TSH in an attempt to stimulate the thyroid, but the gland can’t keep up, so overt hypothyroidism develops for many patients. The standard management is lifelong thyroid hormone replacement with levothyroxine, with regular thyroid function tests to keep TSH and hormone levels in the target range. While some people may still have hyperthyroidism if the dose isn’t sufficient, that’s not the typical long-term outcome. Thyroid cancer risk isn’t a usual long-term consequence of this therapy, and hyponatremia isn’t a direct result of the treatment.