- The l-isomer is the active iodine compound existing normally in the thyroid gland and extracted therefrom in crystalline form for therapeutic use; also prepared synthetically; used for the relief of hypothyroidism, cretinism, and myxedema.- labeled t. SYN: radioactive t..- radioactive t. t. in which a radioisotope of iodine (125I or 131I) is incorporated into its molecule; used in experiments tracing the metabolism of t.. SYN: labeled t., radiolabeled t., radiothyroxin.- radiolabeled t. SYN: radioactive t..- t. sodium a preparation obtained by the action of a limited amount of sodium carbonate upon t.; it contains between 61 and 65% of iodine. See sodium levothyroxine, sodium liothyronine.
* * *thy·rox·ine or thy·rox·in thī-'räk-.sēn, -sən n an iodine containing hormone C15H11I4NO4 that is an amino acid produced by the thyroid gland as a product of the cleavage of thyroglobulin, increases the metabolic rate, and is used to treat thyroid disorders called also T4
* * *n.one of the hormones synthesized and secreted by the thyroid gland (see thyroid hormone). A preparation of thyroxine (levothyroxine sodium) can be administered by mouth to treat underactivity of the thyroid gland.
* * *thy·rox·ine (T4) (thi-rokґsin) L-3,5,3′,5′-tetraiodothyronine, the major hormone elaborated by the thyroid follicular cells, formed from thyroglobulin and transported mainly in the blood serum thyroxine-binding globulin. Its chief function is to increase the rate of cell metabolism. It is also essential for central nervous system maturation and regulates a number of other functions. Thyroxine is deiodinated in peripheral tissues (liver, kidney, and heart) to form triiodothyronine, the active â€œtissueâ€ form of thyroid hormone, which is much more biologically active. A preparation of thyroxine, levothyroxine (q.v.), is used pharmaceutically. Spelled also thyroxin. thyroxinic adj
Medical dictionary. 2011.