**Core Concept**
Radioiodine is a radioactive form of iodine used in nuclear medicine for diagnostic and therapeutic purposes. It selectively targets thyroid tissue, which concentrates iodine, allowing for localized treatment of thyroid disorders.

**Why the Correct Answer is Right**
The correct answer is [insert correct option here]. Radioiodine is preferred for the treatment of hyperthyroidism, especially in cases of Graves' disease, due to its ability to selectively destroy thyroid tissue. This is achieved through the release of beta radiation, which damages the thyroid cells, leading to their apoptosis. The radioactive iodine is taken up by the thyroid gland through the sodium-iodide symporter (NIS), which is highly expressed in thyroid cells.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because radioiodine is not the primary treatment for thyroid cancer, although it may be used in certain cases for palliative purposes.
**Option B:** This option is incorrect because methimazole is an antithyroid medication used to treat hyperthyroidism, but it is not as effective as radioiodine for long-term management.
**Option C:** This option is incorrect because propylthiouracil is another antithyroid medication that may be used to treat hyperthyroidism, but it is not as effective as radioiodine for long-term management.

**Clinical Pearl / High-Yield Fact**
Radioiodine therapy is often associated with a risk of thyroid storm, which is a life-threatening complication of hyperthyroidism. Patients receiving radioiodine therapy should be closely monitored for signs of thyroid storm, such as tachycardia, tremors, and fever.

**Correct Answer:** D. Hyperthyroidism