thyroxine

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thyroxine

 (T4) [thi-rok´sin]
a thyroid hormone that contains iodine and is a derivative of the amino acid tyrosine, occurring naturally as l-thyroxine; its chemical name is tetraiodothyronine. It is formed and stored in the thyroid follicles as thyroglobulin and released from the gland by the action of a proteolytic enzyme. It is deiodinated in peripheral tissues to form triiodothyronine (T3), which has a greater biological activity.



Thyroxine acts as a catalyst in the body and influences a great variety of effects, including metabolic rate (oxygen consumption); growth and development; metabolism of carbohydrates, fats, proteins, electrolytes, and water; vitamin requirements; reproduction; and resistance to infection. Pharmaceutical preparations of thyroxine, extracted from animals or made synthetically, are called levothyroxine.
free thyroxine the fraction of thyroxine in the serum that is not bound to a binding protein.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

thy·rox·ine (T4),

, thyroxin (thī-rok'sēn, -sin),
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.
Farlex Partner Medical Dictionary © Farlex 2012

thyroxine

(thī-rŏk′sēn′, -sĭn) also

thyroxin

(-rŏk′sĭn)
n.
An iodine-containing hormone, C15H11I4NO4, produced by the thyroid gland, that increases the rate of cell metabolism and regulates growth and that is made synthetically for treatment of thyroid disorders.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

thyroxine

T4, 3,5,3',5'-Tetraiodothyronine A hormone that stimulates metabolism and O2 consumption, which is secreted by the thyroid gland in response to TSH–thyrotropin produced in the adenohypophysis–anterior pituitary gland ↑ in Hyperthyroidism, acute thyroiditis, myasthenia gravis, preeclampsia, pregnancy, viral hepatitis, therapy with clofibrate, OCs, estrogens, perphenazine ↓ in Hypothyroidism, malnutrition, vigorous exercise, hypofunction of adenohypophysis–anterior pituitary gland, renal failure, therapy with corticosteroids, chlorpromazine, heparin, lithium, phenytoin, propranolol, reserpine, salicylates, sulfonamides, testosterone, tolbutamide. See Triiodothyronine–T3, Thyroxine-binding globulin.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.

thy·rox·ine

, thyroxin (thī-rok'sēn, -sin)
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, congenital hypothyroidism, and myxedema.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012

thyroxine

The principal thyroid hormone. Thyroxine has four iodine atoms in the molecule and is often known as T4. The sodium salt of thyroxide (levothyroxine) is sold as a drug used to treat thyroid deficiency disorders (hypothyroidism) under the brand name Eltroxin.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005

thyroxine

a complex organic compound containing iodine which is the main hormone produced by the THYROID GLAND.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005

Thyroxine (T 4 )

Thyroid hormone that regulates many essential body processes.
Mentioned in: Hypothyroidism
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.

thy·rox·ine

, thyroxin (thī-rok'sēn, -sin)
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 congenital hypothyroidism, and myxedema.
Medical Dictionary for the Dental Professions © Farlex 2012