GHRP-6: A Ghrelin Mimetic and Growth Hormone Secretagogue in Preclinical Research
Research Use Only. This article is for scientific and educational reference only. All products are sold for research purposes and are not intended for human or animal consumption.
Overview
GHRP-6 (CAS 87616-84-0), or Growth Hormone Releasing Peptide-6, is a synthetic hexapeptide with the sequence His-D-Trp-Ala-Trp-D-Phe-Lys-NH₂. It was among the first synthetic growth hormone secretagogues (GHS) developed and has served as a foundational research tool for understanding the ghrelin receptor (GHS-R1a) and its role in GH regulation, appetite, and energy metabolism.
With a molecular weight of approximately 873 Da, GHRP-6 is significantly smaller than GHRH analogues and acts through an entirely different receptor pathway. Its mechanism is complementary to GHRH-based peptides, and the combination of GHRP-6 with GHRH analogues has been extensively studied as a synergistic approach to GH axis stimulation.
Mechanism of Action
GHRP-6 acts as an agonist at the growth hormone secretagogue receptor type 1a (GHS-R1a), which is the endogenous receptor for ghrelin — the "hunger hormone" produced primarily by the stomach. Activation of GHS-R1a on pituitary somatotrophs stimulates GH release through a mechanism distinct from and complementary to GHRH receptor signaling. GHS-R1a activation increases intracellular calcium via phospholipase C and protein kinase C pathways, while GHRH receptor activation works through the adenylyl cyclase/cAMP pathway.
The combination of GHRH receptor and GHS-R1a activation produces a synergistic increase in GH secretion that exceeds the effect of either pathway alone. GHRP-6 also stimulates GH release by inhibiting somatostatin secretion from the hypothalamus, further amplifying the GH response. Notably, GHS-R1a is also expressed in the hypothalamus, where its activation stimulates appetite — a property that distinguishes GHRP-6 from more selective secretagogues like ipamorelin.
Key Research Findings
GHRP-6 has been extensively characterized in both animal models and human clinical studies. Research has consistently demonstrated robust, dose-dependent increases in GH secretion following GHRP-6 administration, with peak GH levels typically occurring 15–30 minutes post-injection. Studies combining GHRP-6 with GHRH or GHRH analogues have demonstrated 2–5 fold greater GH responses compared to either peptide alone.
Research has also explored GHRP-6's cytoprotective properties independent of its GH-releasing activity. Studies in cardiac ischemia models have reported that GHRP-6 reduces cardiomyocyte apoptosis and infarct size through mechanisms that appear to involve GHS-R1a-mediated activation of survival signaling pathways including PI3K/Akt. Hepatoprotective effects have also been reported in models of liver injury.
The appetite-stimulating properties of GHRP-6, mediated through hypothalamic GHS-R1a activation, have been studied in models of cachexia and anorexia, where the peptide has demonstrated potential to increase food intake and body weight.
Chemical Properties
| Property | Value | |---|---| | Sequence | His-D-Trp-Ala-Trp-D-Phe-Lys-NH₂ | | Molecular Weight | ~873 Da | | CAS Number | 87616-84-0 | | Form | Lyophilized powder | | Purity (research grade) | ≥99% HPLC | | Storage | −20°C, protect from light |
Research Considerations
GHRP-6 is supplied as a lyophilized powder requiring reconstitution with bacteriostatic water. Its relatively small molecular weight and stability make it suitable for a range of research protocols. Researchers should note that GHRP-6 stimulates appetite through GHS-R1a activation, which may be a relevant variable in body composition studies. The peptide's GH-releasing effects are attenuated by elevated blood glucose and free fatty acids, suggesting that fasting state should be standardized in GH research protocols.
Research Use Only. This article is for scientific and educational reference. All products are sold for research purposes only and are not intended for human or animal consumption.