Trijodotyroniini

Trijodotyroniini, also known as T3, is a thyroid hormone that plays a crucial role in regulating metabolism in vertebrates. It is synthesized from tyrosine and iodine atoms. T3 is the more potent and biologically active form of thyroid hormone compared to thyroxine (T4).

The synthesis of T3 occurs primarily in the thyroid gland, but a significant portion is also produced peripherally through the deiodination of T4 in tissues like the liver and kidneys. The thyroid gland secretes both T4 and T3, with T4 being released in larger quantities. However, T3 has a higher affinity for thyroid hormone receptors, making it more influential in cellular processes.

Trijodotyroniini exerts its effects by binding to nuclear receptors, which then regulate gene expression. This regulation impacts a wide range of physiological processes, including growth and development, thermogenesis, heart rate, and carbohydrate and lipid metabolism. It is essential for normal brain development in infants and children.

The levels of T3 in the blood are tightly controlled by the hypothalamic-pituitary-thyroid axis. The hypothalamus releases thyrotropin-releasing hormone (TRH), which stimulates the pituitary gland to release thyroid-stimulating hormone (TSH). TSH, in turn, signals the thyroid gland to produce and release thyroid hormones. High levels of T3 and T4 typically inhibit the release of TRH and TSH, creating a negative feedback loop. Imbalances in T3 levels can lead to various thyroid disorders, such as hyperthyroidism and hypothyroidism.