Thyroid hormone

Article By:

Washington, M. Todd Department of Biochemistry, University of Iowa, Iowa City, Iowa.

Rasmussen, Howard Department of Biochemistry, University of Pennsylvania, Philadelphia, Pennsylvania.

Last reviewed:August 2021

DOI:https://doi.org/10.1036/1097-8542.695900

Any of the chemical messengers produced by the thyroid gland. The thyroid gland is a vertebrate endocrine organ that produces, stores, and secretes the thyroid hormones. For many years, it was generally believed that the thyroid gland produced only two closely related hormones—thyroxine and triiodothyronine (see illustration). In 1961, though, a new hormonal principle, calcitonin (also referred to as thyrocalcitonin), was discovered by Douglas Harold Copp. He originally thought that this substance was secreted by the parathyroid glands. However, in 1963, it was established that the source of calcitonin in mammals was the thyroid gland. Calcitonin was isolated in pure form in 1967 and synthesized in 1968. It is a polypeptide containing a single chain of 32 amino acids, in contrast to thyroxine and triiodothyronine, which are iodinated thyronines. See also: Calcitonin; Hormone; Thyroid gland

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