Thyroid-stimulating hormone, also known as thyrotropin, is a hormone synthesized and secreted by thyrotrope cells in the anterior pituitary gland, which regulates the endocrine function of the thyroid gland. Thyroid-stimulating hormone (TSH) stimulates the thyroid gland to secrete the hormones thyroxine (T₄) and triiodothyronine (T₃). The production of TSH is inhibited by the production of somatostatin by the hypothalamus. T₃ and T₄ also inhibit TSH production and secretion, creating a regulatory negative feedback loop. The release of TSH is stimulated by the production of thyrotropin-releasing hormone (TRH).

In the digram shown here, pink = TSH receptor extracellular domain, green = beta subunit of TSH hormone, blue = alpha subunit of TSH hormone.