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Related to tetraiodothyronine: 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.


Thyroxin, see T4.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Iervasi, "Effects of tetraiodothyronine and triiodothyronine on hamster cheek pouch microcirculation," American Journal of Physiology, vol.
Bile acids increase energy expenditure in brown adipose tissue via the stimulation of TGR5 with subsequent increased conversion of the thyroid hormone tetraiodothyronine (T4) to the active form triiodothyronine (T3) [19, 20] and are also involved in the stimulation of GLP-1 release [10, 20].
Serum[T.sub.3](tri-iodothyronine),[T.sub.4] (tetraiodothyronine), TSH (thyroid stimulating hormone), anti-TPO (thyroid peroxidase) antibody and serum ferritin were determined by immunochemiluminiscence (ICMA Elecsys 2010, Roche, Germany).
"The standard blood tests for thyroid problems are TSH (thyroid stimulating hormone), estimates of free T4 (thyroxine or tetraiodothyronine), total and estimates of free T3 (triiodothyronine), and thyroid antibodies; others are usually not necessary," says Dr.
T3 (triiodothyronine) and T4 (tetraiodothyronine, or thyroxine) are hormones produced by the thyroid.
Free tetraiodothyronine ([FT.sub.4]) serum levels by electrochemiluminescence method in canines
The tyrosines are iodinated at one (monoiodotyrosine) or two (diiodotyrosine) sites and then coupled to form the active thyroid hormones, tetraiodothyronine or thryoxine ([T.sub.4]) and triiodothyronine ([T.sub.3]).
The only confirmed function of iodine is as an essential substrate for the synthesis of thyroid hormones, tetraiodothyronine (thyroxin or [T.sub.4]) and triiodothyronine ([T.sub.3]) (Hetzel, 1989).
Distribution of Cases according to T4 (Tetraiodothyronine) Level Range Overt Subclinical No.
All patients went through endocrine examination regarding pituitary function, including measurements of adrenocorticotropic hormone (ACTH), cortisol, thyroid-stimulating hormone (TSH), free tetraiodothyronine (fT4), growth hormone (GH), insulin-like growth factor 1 (IGF1), FSH/LH, testosterone (T), estradiol (E2), urinary volume, urine, and plasma osmolality.