thyroxine

noun

thy·​rox·​ine thī-ˈräk-ˌsēn 

-sən

variants or thyroxin

: an iodine-containing hormone C₁₅H₁₁I₄NO₄ that is an amino acid produced by the thyroid gland as a product of the cleavage of thyroglobulin, increases metabolic rate, and is used to treat thyroid disorders

called also T4

Examples of thyroxine in a Sentence

Recent Examples on the Web

The association was stronger as thyroxine levels rose. —Kristen Fischer, Health, 7 Dec. 2024

Levothyroxine is prescribed to treat hypothyroidism—where the thyroid doesn't produce enough of the hormone thyroxine—and works by topping up thyroid hormone levels. —Yaakov Katz, Newsweek, 28 Nov. 2024

This hormone sends signals to the thyroid to create the hormones triiodothyronine (T3) and thyroxine (T4). —Dr. Roshini Raj, Health, 14 June 2024

These include thyroid-stimulating hormone, or TSH, which stimulates the thyroid gland to release two other hormones: triiodothyronine, or T3, and thyroxine, or T4. —Brad Reisfeld, Discover Magazine, 12 Feb. 2024

Word History

Etymology

alteration (by substitution of the suffix -ine entry 2 for -in entry 1) of earlier thyroxin, shortened from thyro-oxy-indol, from thyro- + oxy + indole

Note: The name was introduced by the American biochemist Edward Calvin Kendall (1886-1972) in "The thyroid hormone and its relation to the other ductless glands," Endocrinology, vol. 2 (1918), p. 90. The change of suffix was made when it was realized that the compound had an amino acid as a nucleus rather than indole, as Kendall had believed. (See A.T. Cameron, "Designation of thyroxine," Nature, vol. 119, June 25, 1927, p. 925.)

First Known Use

1918, in the meaning defined above

Kids Definition

thyroxine

noun

thy·​rox·​ine

variants or thyroxin

thī-ˈräk-sən 

-ˌsēn

: an iodine-containing hormone that is produced by the thyroid gland and is used to treat thyroid disorders

Medical Definition

thyroxine

noun

thy·​rox·​ine

variants or thyroxin

thī-ˈräk-ˌsēn, -sən 

: an iodine-containing hormone C₁₅H₁₁I₄NO₄ that is an amino acid produced by the thyroid gland as a product of the cleavage of thyroglobulin, that increases the metabolic rate, and that is used to treat thyroid disorders

called also T4