GHRP-1
Growth Hormone AxisAlso known as: Growth Hormone Releasing Peptide 1, His-D-Trp-Ala-Trp-D-Phe-Lys-NH2, GHRP1
Mechanism
GHRP-1 was one of the earliest synthetic growth hormone-releasing peptides discovered, paving the way for better-known successors like GHRP-2, GHRP-6, and Hexarelin. It stimulates the pituitary gland to release growth hormone by activating the ghrelin receptor (GHS-R1a). While it is less commonly used today than its successors (which have been better optimized for potency and side effect profile), it remains available as a research peptide and is historically significant as a foundational compound in the GHS field.
Technical detail
GHRP-1 (His-D-Trp-Ala-Trp-D-Phe-Lys-NH2) is a synthetic hexapeptide growth hormone secretagogue that binds the growth hormone secretagogue receptor 1a (GHS-R1a, the ghrelin receptor). Activates Gq/11-coupled signaling in somatotrophs: phospholipase C → IP3-mediated calcium release from ER → calcium-dependent exocytosis of GH-containing secretory granules. Also suppresses somatostatin tone at the hypothalamic level. D-amino acid residues (D-Trp, D-Phe) confer protease resistance and enhance receptor binding. Compared to later GHRPs: lower potency than GHRP-2 and Hexarelin for GH release; produces less appetite stimulation than GHRP-6 (which has higher ghrelin-mimetic activity). Increases prolactin and cortisol at higher doses (shared class effect). One of the original GHRPs characterized by Bowers et al. in the 1980s.