• synonyms


[thahy-rok-seen, -sin]
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  1. Biochemistry. the thyroid gland hormone that regulates the metabolic rate of the body.
  2. Pharmacology. a commercial form of this compound, obtained from the thyroid glands of animals or synthesized, used in the treatment of hypothyroidism. Symbol: T4
Also thy·rox·in [thahy-rok-sin] /θaɪˈrɒk sɪn/.

Origin of thyroxine

1915–20; thyr- + ox- + in(dol)e (orig. thought to be a chemical component)
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
British Dictionary definitions for thyroxin


thyroxin (θaɪˈrɒksɪn)

  1. the principal hormone produced by the thyroid gland: it increases the metabolic rate of tissues and also controls growth, as in amphibian metamorphosis. It can be synthesized or extracted from the thyroid glands of animals and used to treat hypothyroidism. Chemical name: tetra-iodothyronine; formula: C 15 H 11 I 4 NO 4

Word Origin

C19: from thyro- + oxy- ² + -ine ²
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for thyroxin



from thyro-, comb. form of thyroid, + oxy- + indole + chemical suffix -ine (2). So called from the original description of its composition.

Online Etymology Dictionary, © 2010 Douglas Harper

thyroxin in Medicine


(thī-rŏksēn′, -sĭn)
  1. An iodine-containing hormone that is produced by the thyroid gland, increases the rate of cell metabolism, regulates growth, and is made synthetically for treatment of thyroid disorders.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

thyroxin in Science


[thī-rŏksēn′, -sĭn]
  1. An iodine-containing hormone secreted by the thyroid gland that increases the rate of cell metabolism and regulates growth. Thyroxine can also be made synthetically for treatment of hypothyroidism.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.