MCQ Detailed View

Hormones are chemical messengers secreted by endocrine glands that regulate various physiological processes in the body. Among these hormones, thyroxine is unique because it contains iodine as a key component of its molecular structure. Thyroxine is produced by the thyroid gland, located in the neck, and is essential for regulating metabolism, growth, and development.

Thyroxine’s chemical formula is C₁₅H₁₁I₄NO₄, meaning each molecule contains four iodine atoms. Iodine is crucial for the synthesis of thyroxine, and deficiency of iodine in the diet can lead to goiter (enlargement of the thyroid gland) and other metabolic disorders. This is why iodized salt is commonly recommended to prevent iodine deficiency in populations.

Other hormones listed, such as insulin and adrenaline, do not contain iodine. Insulin, produced by the pancreas, regulates blood glucose levels and is a peptide hormone composed of amino acids without iodine. Adrenaline, secreted by the adrenal glands, is involved in the fight-or-flight response and is derived from the amino acid tyrosine, also without iodine.

Thyroxine plays a key role in cellular energy production, heart rate regulation, and temperature control. It also influences protein synthesis and nervous system development. Because iodine is an essential part of thyroxine, the body must obtain it from dietary sources like iodized salt, seafood, and dairy products.

Understanding which hormones contain iodine is important for studying the endocrine system, metabolism, and nutritional biology. Thyroxine serves as a primary example of how trace elements in the diet directly affect hormone function and overall health.