| Section2 = | Section3 = }} Thyroxine, or 3,5,3',5'-tetra­iodothyronine (often abbreviated as T4), a form of thyroid hormones is the major hormone secreted by the follicular cells of the thyroid gland. T4 is transported in blood, with 99.95% of the secreted T4 being protein bound, principally to thyroxine-binding globulin (TBG), and, to a lesser extent, to transthyretin and serum albumin. T4 is involved in controlling the rate of metabolic processes in the body and influencing physical… (More on Thyroxine)