tetrajodotyroniny

Tetrajodotyronina, also known as thyroxine or T4, is a thyroid hormone. It is one of the two major hormones produced by the thyroid gland, the other being triiodothyronine (T3). T4 contains four iodine atoms, hence its name. The thyroid gland synthesizes T4 from tyrosine and iodine. In the bloodstream, T4 is largely bound to proteins, with only a small fraction circulating in its free form. T4 is considered a prohormone, as it is converted to the more active form, T3, in target tissues through deiodination. Thyroid hormones play a crucial role in regulating metabolism, growth, and development in vertebrates. They influence the rate at which cells use energy and are essential for normal brain development, particularly in infants and children. T4 levels are often measured in blood tests to assess thyroid function. Both high and low levels of T4 can indicate various thyroid disorders. The synthesis and release of T4 are regulated by the hypothalamus and pituitary gland through the thyroid-stimulating hormone (TSH).