triiodotüroniin

Triiodothyronine, often abbreviated as T3, is a thyroid hormone that plays a crucial role in regulating the body's metabolism. It is one of two major hormones produced by the thyroid gland, the other being thyroxine (T4). T3 is the more potent and biologically active form of the two.

The thyroid gland synthesizes T3 and T4 from tyrosine and iodine. While the thyroid produces both hormones, it releases significantly more T4 than T3. The majority of T3 in the bloodstream is actually derived from the conversion of T4 in peripheral tissues through a process called deiodination. Enzymes known as deiodinases catalyze this conversion.

T3 exerts its effects by binding to specific nuclear receptors within cells. This binding influences gene expression, leading to changes in the rates of various metabolic processes. These processes include carbohydrate and lipid metabolism, protein synthesis, and heat production. T3 is essential for normal growth and development, particularly in the nervous system and skeletal development during fetal life and childhood.

In adults, T3 influences heart rate, body temperature, and energy levels. Imbalances in T3 levels can lead to thyroid disorders. Hyperthyroidism, characterized by excessive thyroid hormone production, can result in symptoms like weight loss, rapid heartbeat, and anxiety. Hypothyroidism, on the other hand, involves insufficient thyroid hormone production and can cause fatigue, weight gain, and a slowed metabolism. Blood tests measuring T3 and T4 levels, along with TSH (thyroid-stimulating hormone), are commonly used to diagnose thyroid conditions.