All statements about iodine are true EXCEPT which of the following?

All statements about iodine are true EXCEPT which of the following?

• A. Radioactive iodine treatment of Graves' disease is effective in less than 40% of patients treated with this agent.
• B. Iodine deficiency is one of the most common causes of hypothyroidism in the world.
• C. T4 has 4 iodine molecules.
• D. RAIU is often useful in determining the cause of thyrotoxicosis.

Answer: (A)

Radioactive iodine therapy is a standard, effective treatment for Graves’ disease in the majority of patients, with most achieving resolution of hyperthyroidism after therapy—often after a single dose. The claim that its effectiveness is less than 40% does not fit this evidence, making that statement the exception. Iodine biology underpins several true points: iodine deficiency remains one of the most common causes of hypothyroidism worldwide; thyroxine (T4) contains four iodine atoms; and radioactive iodine uptake testing (RAIU) is useful in determining the cause of thyrotoxicosis because different patterns appear for Graves’ disease (diffuse uptake), toxic nodular disease (focal uptake), and thyroiditis (low uptake).

Radioactive iodine therapy is a standard, effective treatment for Graves’ disease in the majority of patients, with most achieving resolution of hyperthyroidism after therapy—often after a single dose. The claim that its effectiveness is less than 40% does not fit this evidence, making that statement the exception. Iodine biology underpins several true points: iodine deficiency remains one of the most common causes of hypothyroidism worldwide; thyroxine (T4) contains four iodine atoms; and radioactive iodine uptake testing (RAIU) is useful in determining the cause of thyrotoxicosis because different patterns appear for Graves’ disease (diffuse uptake), toxic nodular disease (focal uptake), and thyroiditis (low uptake).