Trijodotüroniin

Trijodotüroniin, also known as T3, is a thyroid hormone. It is one of two principal hormones produced by the thyroid gland, the other being thyroxine (T4). T3 plays a critical role in regulating metabolism, heart rate, and body temperature in vertebrates.

The synthesis of trijodotüroniin involves the iodination of tyrosine residues within the thyroglobulin protein, followed by enzymatic cleavage. While the thyroid gland produces both T4 and T3, T3 is considered the more biologically active form. A significant portion of circulating T3 is actually derived from the peripheral deiodination of T4, a process catalyzed by deiodinase enzymes.

T3 exerts its effects by binding to thyroid hormone receptors, which are nuclear receptors. Once bound, these receptors can influence gene expression, affecting a wide range of cellular processes. Its functions include promoting growth and development, increasing oxygen consumption, and influencing carbohydrate, lipid, and protein metabolism.

Disruptions in T3 levels can lead to various health conditions. Hyperthyroidism, characterized by excessive thyroid hormone production, can result in symptoms such as weight loss, rapid heartbeat, and anxiety. Conversely, hypothyroidism, a deficiency in thyroid hormones, can cause fatigue, weight gain, and slowed metabolism. The assessment of T3 levels is an important component of thyroid function tests used in the diagnosis and management of these disorders.