Iodine is essential for the normal production of which hormone?

• A. Adrenaline
• B. Insulin
• C. Thyroxine
• D. Testosterone

Answer: (C)

Iodine is required to make thyroid hormones in the thyroid gland. The thyroid uses iodine to attach to tyrosine residues on thyroglobulin, forming the hormones thyroxine (T4) and triiodothyronine (T3). Among these, thyroxine is the hormone whose production depends on iodine. These thyroid hormones help regulate metabolism, growth, and development. If iodine is deficient, thyroid hormone production drops, leading to hypothyroidism and possible goiter. The other hormones listed—adrenaline, insulin, and testosterone—are produced by different glands and do not require iodine for their synthesis.