Thyroid

The thyroid is an endocrine gland at the front of the neck that produces hormones regulating metabolism, growth, and other bodily functions.

Thyroid hormone: Hormones produced by the thyroid that influence metabolism, development, and other bodily functions. The gland’s main products circulate to regulate activity across many tissues.
Thyroid follicle: A spherical unit of thyroid tissue lined by epithelial cells around a lumen filled with colloid. Follicles are the gland’s hormone-producing units and store hormone precursors in their lumens.
Hypothyroidism: A condition in which thyroid hormone levels or effects are insufficient for the body’s needs. Reduced output from the gland is a common cause of this disorder.
Graves disease: An autoimmune disease in which antibodies stimulate the thyroid-stimulating hormone receptor, often causing hyperthyroidism. It is a specific immune-driven cause of excessive thyroid activity.
Thyroxine: The thyroid hormone T4, a circulating precursor that can be converted into the more active T3. Thyroid follicular cells release T4 as the gland’s principal hormone product.
Thyroglobulin: A large protein made by thyroid follicular cells that serves as the scaffold for thyroid hormone synthesis. Follicular cells iodinate and modify this protein before releasing thyroid hormones.
Hyperthyroidism: A condition in which the body is exposed to excessive thyroid hormone activity. Overproduction by the gland can accelerate metabolism and affect multiple organs.
Hashimoto thyroiditis: An autoimmune disorder that progressively damages the thyroid and commonly causes hypothyroidism. It is a specific immune-mediated cause of declining thyroid function.
Triiodothyronine: The thyroid hormone T3, which binds thyroid hormone receptors and alters gene expression. The gland produces T3 directly and supplies T4 that tissues convert into T3.
Thyroid peroxidase: An enzyme that oxidizes iodide and catalyzes its attachment to tyrosine residues in thyroglobulin. This enzyme carries out key chemical steps in the gland’s hormone synthesis.

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