Tetrajódtironin

Tetrajódtironin, also known as thyroxine or T4, is a hormone produced by the thyroid gland. It plays a crucial role in regulating metabolism in the human body. T4 is one of two major hormones secreted by the thyroid, the other being triiodothyronine (T3). T4 is the more abundant of the two, but T3 is considered more potent.

The synthesis of tetrajódtironin begins with tyrosine and iodine. The thyroid gland actively takes up iodine from the bloodstream. This iodine is then incorporated into tyrosine molecules to form monoiodotyrosine (MIT) and diiodotyrosine (DIT). Two molecules of DIT then couple to form thyroxine. T4 is released into the bloodstream, where it circulates to various tissues.

Once in the target tissues, tetrajódtironin can be converted into triiodothyronine (T3) through deiodination, a process that removes one iodine atom. T3 is the form that primarily interacts with cellular receptors to exert its effects. These effects include regulating heart rate, body temperature, growth and development, and the rate at which the body uses energy.

The production of T4 is controlled by the pituitary gland through thyroid-stimulating hormone (TSH). When T4 levels in the blood are low, the pituitary releases more TSH, stimulating the thyroid to produce more T4. Conversely, high levels of T4 inhibit TSH release. This feedback loop helps maintain stable hormone levels in the body. Imbalances in tetrajódtironin production can lead to conditions like hyperthyroidism or hypothyroidism.