GHRP-6 is a research compound studied for its role in performance & hormone research. This page covers mechanism of action, published studies, preclinical protocols, and analytical specifications.
Quick Reference: GHRP-6
CAS Number
87616-84-0
Molecular Formula
C46H56N12O6
Molecular Weight
873.0 g/mol
Sequence / Structure
His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 (hexapeptide)
Physical Form
Lyophilized powder
Purity (QSC)
≥99%
Storage
Store lyophilized at -20°C. Reconstituted: 4°C, use within 28 days.
Reconstitution
Add 2ml bacteriostatic water per vial. Swirl gently to dissolve.
Mechanism of Action
GHRP-6 (Growth Hormone-Releasing Peptide 6) is a synthetic hexapeptide and one of the original GH secretagogues developed through the enkephalin analogue research programme in the 1980s. It was the first peptide demonstrated to stimulate GH release through a receptor distinct from the GHRH receptor — a finding that eventually led to the identification of the ghrelin receptor (GHSR-1a).
GHSR-1a Agonism and Orexigenic Activity: GHRP-6 binds GHSR-1a with high affinity. Its defining research characteristic is its potent orexigenic (appetite-stimulating) effect, which is significantly stronger than GHRP-2 and far greater than ipamorelin. This orexigenic activity is mediated through GHSR-1a activation in the hypothalamic arcuate nucleus, where ghrelin receptor signalling drives NPY and AgRP co-release — the primary appetite-stimulating neurons in the central energy regulation circuit.
GH Release Mechanism: GHRP-6 activates the same PLC-IP3-calcium pathway as GHRP-2 through Gq-protein-coupled GHSR-1a signalling, producing GH release from pituitary somatotrophs. GH pulse amplitude with GHRP-6 is comparable to GHRP-2 and greater than ipamorelin at equivalent molar doses.
Cortisol and Prolactin Co-stimulation: Like GHRP-2, GHRP-6 produces significant cortisol and prolactin co-stimulation alongside GH release — more pronounced than GHRP-2 in some protocols. This HPA axis activation is a confound in anabolic research but is intentionally utilised in studies examining the orexigenic and metabolic effects of ghrelin receptor activation independent of GH.
Research Applications
Appetite and Energy Regulation Research: GHRP-6’s strong orexigenic activity makes it the preferred GH secretagogue for research specifically studying hypothalamic appetite circuits, NPY/AgRP neuron activation, and ghrelin receptor-mediated food intake regulation.
GI Motility Research: Ghrelin receptors are highly expressed in the GI tract, and GHRP-6 has been studied in gastric motility models. Research has examined its prokinetic effects in postoperative ileus and gastroparesis models.
Original GHSR Characterisation: GHRP-6 was the tool compound that led to the identification of the ghrelin receptor in 1999, making it historically central to the GHSR pharmacology literature.
Selectivity Reference Point: In the ipamorelin vs GHRP-2 vs GHRP-6 selectivity comparison series, GHRP-6 represents the least selective end of the spectrum — used as the “dirty” reference compound against which more selective GHRPs are compared.
Cytoprotection Research: Emerging research has examined GHRP-6 in models of hepatic and cardiac injury for potential cytoprotective effects mediated through non-GHSR mechanisms, including CD36 and TGF-β pathway modulation.
Key Published Research
Primary publications relevant to GHRP-6 research. Full citations available via PubMed. QSC does not endorse or make claims based on this research.
Bowers et al. (1991)
“Synergistic Secretion of Growth Hormone by MK-0677 and GHRP-6” — Endocrinology
Establishes the GHRP-6 pharmacological profile and the synergistic GH release when combined with GHRH — foundational to dual-pathway GH secretagogue research.
Howard et al. (1996)
“A Receptor in Pituitary and Hypothalamus that Functions in Growth Hormone Release” — Science
The landmark paper identifying the GHSR, largely enabled by GHRP-6 as the tool compound — one of the most cited papers in endocrinology.
Gualillo et al. (2003)
“Ghrelin, a Novel Placental-Derived Hormone” — Endocrinology
Contextualises GHRP-6 within the broader ghrelin receptor biology and appetite regulation literature.
Parallel group; endpoints: GH, cortisol, prolactin, food intake AUC at 60–120 min
In Vitro GHSR (Ghrelin Receptor)
0.1–100 nM
Added to cell assay
Competitive binding and calcium mobilisation assays for GHSR-1a pharmacology
Frequently Asked Questions
What is GHRP-6?
GHRP-6 is a synthetic hexapeptide GHSR-1a agonist — one of the original GH secretagogues, historically important as the tool compound used to identify the ghrelin receptor. It produces GH release alongside significant appetite stimulation and cortisol/prolactin co-stimulation.
What is the difference between GHRP-6 and GHRP-2?
Both are GHSR-1a agonists, but GHRP-6 has a stronger orexigenic (appetite-stimulating) effect mediated by more potent hypothalamic ghrelin receptor activation. GHRP-2 has slightly higher GH selectivity. In research where appetite effects would confound results, GHRP-2 or ipamorelin are preferred.
What is the difference between GHRP-6 and ipamorelin?
GHRP-6 produces strong appetite stimulation, significant cortisol and prolactin co-stimulation alongside GH release. Ipamorelin produces equivalent GH release with minimal cortisol/prolactin/appetite co-stimulation — the highest-selectivity GHSR agonist in research use. For isolated GH axis studies, ipamorelin is the cleaner tool.
How should GHRP-6 be stored?
Lyophilized at -20°C. After reconstitution with bacteriostatic water, store at 4°C and use within 28 days.
What purity is QSC GHRP-6?
≥99% by HPLC and mass spectrometry. COA on product page, Janoshik-verified.
Research Use Only: All products sold on qsc-usa.com are intended strictly for laboratory research purposes only. They are not approved for human consumption, veterinary use, or any other application. Researchers are responsible for understanding and complying with local regulations in their jurisdiction.
