GHRP-1

Growth Hormone Axis

Also known as: Growth Hormone Releasing Peptide 1, His-D-Trp-Ala-Trp-D-Phe-Lys-NH2, GHRP1

Growth Hormone SecretagoguesResearch phase: Preclinical, Phase I/II dataRegulatory: Not approved by any regulatory agency. Research peptide. Less commonly used clinically than GHRP-2, GHRP-6, or Hexarelin. Historical significance as early GHS compound.

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.

Evidence

Determination of growth hormone releasing peptides metabolites in human urine after nasal administration of GHRP-1, GHRP-2, GHRP-6, Hexarelin, and Ipamorelin.
Semenistaya E, Zvereva I, Thomas A, Thevis M, Krotov G, Rodchenkov G. (2015) — Drug Test Anal — PMID: 25869809
The study investigated the metabolites of GHRP-1, GHRP-2, GHRP-6, Hexarelin, and Ipamorelin in human urine after nasal administration. It identified several metabolites for each compound and developed a method for their detection.
emerging
Effects in vitro of New Growth Hormone Releasing Peptide (GHRP-1) on Growth Hormone Secretion from Ovine Pituitary Cells in Primary Culture
Authors not listed in queue metadata (1994) — Journal of Neuroendocrinology — PMID: 10.1111/j.1365-2826.1994.tb00571.x
Primary ovine pituitary perifusion experiments found GHRP-1 stimulated growth hormone release in a dose-dependent manner with potency similar to GHRP-6 but lower than GRF, and data suggested a calcium-dependent mechanism distinct from the GRF receptor pathway.
moderate
GROWTH HORMONE (GH) SECRETION AND GH RESPONSE TO GH-RELEASING PEPTIDE 1 (GHRP-1) IN PUERPERAL WOMEN
(1993) — Springer Science and Business Media LLC — PMID: 10.1203/00006450-199305001-00402
Puerperal women have lower GH peaks and higher GH troughs compared to mid-cycle women. The GH response to GHRP-1 was significantly lower in puerperal women.
emerging

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