GHSR
The ghrelin receptor — G-protein-coupled receptor through which GHRPs and ibutamoren stimulate GH release.
For laboratory and research use only — not for human consumption.
The growth-hormone secretagogue receptor (GHSR, also known as the ghrelin receptor or GHS-R1a) is a 366-amino-acid class A G-protein-coupled receptor expressed prominently on anterior-pituitary somatotrophs, hypothalamic arcuate neurons, and in lower density across the gastrointestinal tract, pancreas, and central reward circuits. Its endogenous ligand is ghrelin, the 28-amino-acid 'hunger hormone' secreted by gastric oxyntic cells and acylated at Ser-3 to form the bioactive form. GHSR activation in somatotrophs raises intracellular calcium via Gq/PLC/IP₃ signalling, triggering growth-hormone release in a manner that is synergistic with — and independent of — GHRH-pathway stimulation. Pharmacologically, GHSR is the principal molecular target of the GHRP class (GHRP-2, GHRP-6, ipamorelin, hexarelin) and of the orally bioavailable small-molecule MK-677 (ibutamoren). GHSR also has constitutive (ligand-independent) activity that may contribute to baseline GH tone and is a target of ongoing pharmacological development. The receptor's expression in reward circuits and its modulation of appetite via GHRP-6 (notable orexigenic effect) versus the receptor-selectivity advantage of ipamorelin (minimal appetite stimulation) explain the differential profiles within the GHRP class.