UCSD Molecule Pages

The TSH receptor is a member of the G protein-coupled receptor(GPCR)family. It is one of the glycoprotein hormone receptors, which also includes the FSH and LH/CG receptors. The TSH receptor mediates the action of the pituitary-derived glycoprotein, TSH (thyroid stimulating hormone, thyrotropin or thyrotrophin). TSH binds to the TSH receptor which is located on thyroid follicular cells (but is also expressed in extrathyroidal sites). Glycosylation of the TSH receptor occurs, as does cleavage of the receptor from an intact to an extracellular form (α subunit), which may be shed after deletion of a short region (aa 316-366) near the C terminal of the extracellular domain, thus leaving a transmembrane form (β subunit). The α subunit is responsible for ligand/autoantibody binding, facilitated by glycosylation and possibly by the extracellular loops of the 7 transmembrane segments. The intracellular loops of the β subunit interact with G proteins when the receptor is activated. The receptor may also exist in multimeric forms, although it is not clear whether these forms play a role in TSH receptor function. TSH action involves cAMP and IP/DAG responses. The TSH receptor controls positively both the function (production of thyroid hormones T3 and T4) and growth of the thyroid.