Thyroglobulin

A protein found in the thyroid gland. Some thyroglobulin can be found in the blood, and this amount may be measured after thyroid surgery to determine whether thyroid cancer has recurred. Thyroglobulin derived from pig thyroid glands is sometimes given to treat thyroid dysfunction. Abbreviated Tg.

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1. A protein that contains precursors of thyroid hormone usually stored in the colloid within the thyroid follicles; biosynthesis of thyroid hormone entails iodination of the l-tyrosyl moieties of this protein and the combination of two iodotyrosines to form thyroxine, the fully iodinated thyronine; secretion of thyroid hormone requires proteolytic degradation of t., with the attendant release of free hormone; a defect in t. metabolism will lead to hypothyroidism. SYN: iodoglobulin, thyroprotein (1). 2. A substance obtained by the fractionation of thyroid glands from the hog, Sus scrofa, containing not less than 0.7% of total iodine; used as a thyroid hormone in the treatment of hypothyroidism.

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thy·ro·glob·u·lin .thī-rō-'gläb-yə-lən n an iodine-containing protein of the thyroid gland that on proteolysis yields thyroxine and triiodothyronine

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n.

a protein in the thyroid gland from which the thyroid hormone (thyroxine and triiodotyrosine) are synthesized.

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thy·ro·glob·u·lin (Tg) (thi-ro-globґu-lin) an iodine-containing glycoprotein of high molecular weight found in the colloid of thyroid gland follicles; it is made by thyroid follicular cells and secreted into the follicular lumen where it is iodinated, after which its iodinated tyrosyl moieties form the iodothyronines thyroxine and triiodothyronine. Thyroglobulins are then taken up by endocytosis into the follicular cells, where the iodothyronines are liberated by proteolysis, followed by release into the extracellular fluid and thence to the bloodstream.