Thyreotropin

Thyreotropin, also known as thyroid-stimulating hormone (TSH), is a glycoprotein hormone crucial for the regulation of thyroid gland function. It is produced and secreted by the anterior pituitary gland, a small primary endocrine gland located at the base of the brain. Thyreotropin plays a vital role in controlling the synthesis and release of thyroid hormones, primarily thyroxine (T4) and triiodothyronine (T3), which are essential for maintaining metabolic homeostasis.

The primary function of thyreotropin is to stimulate the thyroid gland to produce and release thyroid hormones. These hormones influence numerous physiological processes, including metabolism, growth, and development. TSH secretion is regulated by the hypothalamus via thyrotropin-releasing hormone (TRH). When circulating levels of T3 and T4 are low, TRH stimulates the release of TSH to increase thyroid hormone production. Conversely, elevated levels of T3 and T4 inhibit TSH secretion through negative feedback mechanisms.

Thyreotropin is used clinically in diagnostic testing to assess thyroid function. Elevated TSH levels often indicate hypothyroidism, where the thyroid gland is underactive, while low levels suggest hyperthyroidism or other thyroid dysfunctions. The measurement of TSH is a primary tool in diagnosing thyroid disorders and monitoring treatment.

Structurally, thyreotropin consists of two subunits, alpha and beta, with the beta subunit conferring biological specificity. The hormone’s molecular weight varies depending on species but generally ranges around 28 to 30 kDa in humans.

Overall, thyreotropin is a key hormone in the endocrine system, essential for the regulation of thyroid activity and overall metabolic balance.