Which of the following is a function of iodine?

• A. Glucose metabolism.
• B. Thyroid hormone synthesis.
• C. Oxygen transport.
• D. B vitamin synthesis.

Answer: (B)

Verified step by step guidance

1. Understand the role of iodine in the body: Iodine is an essential trace mineral primarily involved in the synthesis of thyroid hormones, which regulate metabolism, growth, and development.
2. Eliminate incorrect options: Glucose metabolism is primarily regulated by insulin and other hormones, not iodine. Oxygen transport is facilitated by hemoglobin in red blood cells, which requires iron, not iodine. B vitamin synthesis is not dependent on iodine; B vitamins are obtained from dietary sources.
3. Focus on the correct function: Iodine is a critical component of the thyroid hormones thyroxine (T4) and triiodothyronine (T3). These hormones are synthesized in the thyroid gland and require iodine for their production.
4. Relate iodine deficiency to thyroid function: A lack of iodine can lead to hypothyroidism or goiter, which are conditions caused by insufficient thyroid hormone production.
5. Conclude that the correct answer is 'Thyroid hormone synthesis,' as this is the primary and well-established function of iodine in human nutrition.