Growth Hormone Releasing Peptide (GHRP)
A class of short synthetic peptides (typically 6-7 amino acids) that stimulate growth hormone release by activating the ghrelin receptor. Well-known GHRPs include GHRP-2, GHRP-6, ipamorelin, and hexarelin. No GHRP has received full therapeutic approval in major markets.
Technical Context
GHRPs are typically 6-7 amino acid synthetic peptides that activate the ghrelin receptor (GHS-R1a) on pituitary somatotrophs. Key GHRPs and their distinguishing features: GHRP-6 (His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 — the first GHRP, strong appetite stimulation via GHS-R, increases cortisol and prolactin), GHRP-2 (D-Ala-D-βNal-Ala-Trp-D-Phe-Lys-NH2 — most potent GHRP, moderate appetite/cortisol effects), ipamorelin (Aib-His-D-2-Nal-D-Phe-Lys-NH2 — most selective, minimal appetite/cortisol/prolactin elevation, considered cleanest GH stimulus), hexarelin (His-D-2MeTrp-Ala-Trp-D-Phe-Lys-NH2 — high potency, significant cortisol/prolactin effects, notable tachyphylaxis with chronic use). Ipamorelin's selectivity profile has made it the most discussed GHRP in research peptide communities. None are approved for therapeutic use in major markets. MK-677 (ibutamoren) is often discussed alongside GHRPs but is a non-peptide oral GHS-R agonist.