Thyroxine synthesis occurs in the follicular cells of the thyroid gland. The process begins with the uptake of iodide from the bloodstream, which is then oxidized to iodine. This iodine is incorporated into tyrosine residues on thyroglobulin, forming monoiodotyrosine (MIT) and diiodotyrosine (DIT). Coupling of MIT and DIT forms T3 (triiodothyronine), while coupling of two DIT molecules forms T4 (thyroxine). These iodinated thyroglobulins are stored in the colloid of the thyroid follicles until needed.
