Which substance do the thyroid glands utilize to produce T3 and T4 hormones?

The thyroid glands utilize iodine to produce the hormones T3 (triiodothyronine) and T4 (thyroxine). Iodine is an essential component of these hormones; the thyroid cells extract iodine from the bloodstream and incorporate it into the amino acid tyrosine, which leads to the formation of T3 and T4.

These hormones are crucial in regulating metabolism, growth, and development throughout the body. Sufficient iodine intake is vital for normal thyroid function, which is why a deficiency in iodine can lead to conditions such as goiter and hypothyroidism. The importance of iodine in hormone synthesis highlights its role in overall health and the necessity of ensuring adequate levels in the diet through sources such as iodized salt, seafood, and dairy products.

The other substances listed do not play a direct role in the synthesis of T3 and T4. Sodium, calcium, and chloride are electrolytes and have their own important physiological roles, but they do not contribute to the production of thyroid hormones.