GHRP-6 (Growth Hormone-Releasing Peptide-6) is a synthetic hexapeptide with the sequence His-D-Trp-Ala-Trp-D-Phe-Lys-NH₂. It acts as a potent growth hormone secretagogue and ghrelin mimetic.1
Mechanism of Action
GHRP-6 binds to the ghrelin receptor (GHS-R1a, formerly the growth hormone secretagogue receptor) in the pituitary gland and hypothalamus. This triggers intracellular signaling (primarily via protein kinase C and calcium mobilization) that stimulates pulsatile release of endogenous growth hormone (GH). It operates through a pathway distinct from Growth Hormone-Releasing Hormone (GHRH) and does not possess opioid activity. It also interacts with the CD36 receptor, which contributes to many of its non-GH-mediated effects, such as cytoprotection.1
In research models, it potently elevates GH levels (often synergistically with GHRH), increases IGF-1, and mimics aspects of ghrelin signaling, including appetite stimulation.2
Key Research Areas and Observed Effects
Preclinical (animal) and early clinical studies have explored GHRP-6 for:
GH release and anabolic effects — Robust, dose-dependent GH secretion; potential improvements in body composition, muscle growth, and energy metabolism in models.
Cytoprotection and tissue repair — Strong evidence of protecting organs (heart, liver, kidneys, gut) from ischemia/reperfusion injury, oxidative stress, and chemotherapy toxicity (e.g., doxorubicin). It reduces cell death, preserves mitochondrial function, upregulates antioxidant defenses and prosurvival genes (e.g., Bcl-2), and limits fibrosis.3
Cardioprotection — In animal models of myocardial infarction, heart failure, and doxorubicin-induced cardiomyopathy, it attenuates ventricular remodeling, reduces fibrosis/scarring, preserves ejection fraction, improves survival, and limits inflammatory damage. These effects appear mediated by both GH/IGF-1 and direct receptor actions (CD36, anti-inflammatory pathways).4
Anti-inflammatory and anti-fibrotic — Downregulates pro-fibrotic and inflammatory markers (TGF-β, NF-κB, CTGF); attenuates ROS and supports antioxidant systems.5
Other — Potential roles in wound healing, acute kidney injury, metabolic regulation, and neuroprotection in various models. It also strongly stimulates appetite via ghrelin-like activity.
