Which element is essential for thyroid hormone production and has symbol I with atomic number 53?

• A. Iron
• B. Iodine
• C. Calcium
• D. Potassium

Answer: (B)

Iodine is essential for thyroid hormone production. The thyroid makes the hormones T3 and T4 by incorporating iodine into tyrosine residues on thyroglobulin. Iodine is transported into the thyroid by the sodium-iodide symporter, then binds to tyrosines to form MIT and DIT, which couple to create T3 (MIT + DIT) and T4 (DIT + DIT). After thyroglobulin is processed, these hormones are released into the bloodstream. Without enough iodine, the thyroid can’t synthesize adequate T3 and T4, leading to goiter and potential hypothyroidism; iodine deficiency is a common cause of thyroid problems in some regions, while adequate intake—via iodized salt, seafood, dairy, and certain grains—prevents it. The element with symbol I and atomic number 53 is iodine, the nutrient directly needed for making thyroid hormones. Other minerals like iron, calcium, and potassium are vital for different bodily functions but aren’t directly involved in thyroid hormone synthesis.