Thyroid-Stimulating Hormone (TSH), also known as thyrotropin, is a member of the glycoprotein hormone family, constituting a subset of the cystine-knot growth factor superfamily. TSH is secreted by thyrotrope cells in the anterior pituitary gland and released into circulation in a pulsatile manner. TSH is a glycoprotein hormone composed of two subunits which are non covalently bound to one another. The alpha subunit of TSH is also present in two other pituitary glycoprotein hormones, follicle stimulating hormone and luteinizing hormone, and, in primates, in the placental hormone chorionic gonadotropin. It stimulates thyroid functions using a specific membrane TSH receptor (TSHR) that belongs to the superfamily of G protein-coupled receptors (GPCRs). TSH beta is the beta subunit of thyroid stimulating hormone. Anti-TSH stains thyrotrophs and is useful for categorizing pituitary tumors, as well as for recognizing primary and metastatic pituitary gland tumors. Anti-TSH antibodies may be useful in classification of pituitary tumors.