GHRP-6
Research OnlyA first-generation growth hormone secretagogue that stimulates GH release through the ghrelin receptor. Less selective than newer alternatives with effects on cortisol and prolactin. Historically significant as the peptide that led to ghrelin discovery. Cuban CIGB leads global cytoprotective research. Not approved for any indication.
Growth Hormone Releasing Peptide-6 · SKF-110679 · Growth Hormone-Releasing Hexapeptide
12 human studies
- Preclinical
- 40%
- Clinical
- 27%
Based on 45 cited sources
clinically demonstrated · low confidence
Demonstrated effect magnitude — not a recommendation or safety claim.
Research Depth 52: best human evidence is small surrogate-endpoint controlled studies / RCTs of GH secretion (Hayashi 1991 dose-related GH rise 1915110; Pandya 1998 GHRH-antagonist RCT n=9 9543138; Popovic 1995 7883854; Frieboes 1999 10336729), so 1A=25 (single RCT n<50), 1B=9 (some-concerns, no low-RoB outcome RCT), 1C=5 (total human N in the 50-300 band, tiny per-study samples), 1D=6 (right population but surrogate GH/IGF-I and diagnostic use, not a therapeutic outcome), 1E=7 (substantial CIGB multi-model preclinical program). Mechanism 94: 2A=40 (GHS-R1a named, binding+functional, and GHRH antagonist / hypothalamopituitary disconnection abolish the response 9543138/7883854), 2B=27 (full Gq/11->PLC->IP3/DAG->Ca2+->GH exocytosis chain mapped, Devesa 33776931), 2C=17 (monotonic dose-response in humans + animals in vivo), 2D=10 (confirmed in human + rat in vivo). Plausibility 82: 3A=28 (mechanism->surrogate GH established, surrogate->clinical benefit inferred), 3B=24 (fully coherent with ghrelin/GH endocrinology), 3C=20 (multiple same-class GHRPs reliably release GH), 3D=10 (moderately broad: GH + appetite + preclinical cardioprotection). Global Coverage 73: 4A=28 (replicated across independent groups in Japan, US, Serbia/Spain, Germany, Cuba, China), 4B=22 (many countries), 4C=18 (~45 studies, 20-100 band), 4D=5 (no approval; only a Phase I/II EGF+GHRP-6 stroke trial registration). Community Experience 63: 5A=18 (niche/moderate discussion, community often defers to GHRP-2/ipamorelin), 5B=23 (>7 years sustained use), 5C=14 (broadly consistent themes), 5D=8 (isolated/minor adverse reports: appetite, water retention, cortisol, lethargy). Effectiveness basis clinical (low): a quantified human efficacy estimate exists (marked GH/IGF-I rise, Hayashi 1915110) but it is a surrogate pharmacodynamic endpoint with no demonstrated clinical-outcome benefit and no approval, so E1 large on the surrogate, E2/E3 low (surrogate, no MCID), E4 superiority vs placebo on surrogate only.
GHRP-6 stimulates growth hormone release by activating the ghrelin receptor (GHS-R1a), the same receptor that responds to the endogenous “hunger hormone” ghrelin. Discovered in 1984 before ghrelin itself was identified, GHRP-6 is historically significant as the compound that led to the discovery of the entire ghrelin/GHS system through “reverse pharmacology.”
How It Works (Simplified)
GHRP-6 acts as a potent signal for growth hormone release through multiple interconnected pathways:
Binds to GHS-R1a on pituitary somatotrophs, triggering calcium release and direct GH secretion independent of cAMP pathways.
Acts primarily at the hypothalamus to stimulate GHRH neurons, creating a synergistic amplification of growth hormone release.
Activates NPY/AgRP neurons in the arcuate nucleus, producing strong orexigenic (hunger-inducing) effects via the same pathway as natural ghrelin.
Binds to CD36 scavenger receptor on cardiomyocytes, potentially providing GH-independent cytoprotective effects through Bcl-2 upregulation.
Key Research: Pandya et al. (1998) demonstrated that GHRP-6 requires endogenous GHRH for maximal effect, and patients with hypothalamopituitary disconnection show blocked responses. PMID:9543138
Important Limitations
- Less selective than newer GHRPs (ipamorelin) - also increases cortisol and prolactin
- Strong appetite stimulation may be undesirable for many applications
- No long-term human safety data available
- Cytoprotective effects remain preclinical only despite promising animal data
- Human pharmacokinetics characterized but optimal therapeutic dosing unknown
- Not approved by any regulatory agency; WADA prohibited substance
Reported positives
- Strong appetite stimulation valued for bulking phases
- Improved sleep and recovery reported
- Affordable compared to other GH-related peptides
- Fast onset of GH release
Reported negatives
- Extreme hunger can be overwhelming
- Cortisol elevation greater than GHRP-2
- Water retention and bloating significant
- Lethargy after injection reported
“Known for extreme appetite stimulation. FDA Category 2 restricted. Community often recommends GHRP-2 or ipamorelin instead.”
Self-reported, unverified accounts — not clinical evidence and no substitute for the cited research. Anecdotes are prone to selection bias and placebo effects.
Rapid GH release begins within minutes of administration, with a marked rise in plasma GH after intravenous dosing in healthy men.
PMID:1915110Transient increases in cortisol and ACTH. Appetite stimulation begins. Mild flushing may occur in some subjects.
PMID:9285939GH levels return toward baseline. Elimination half-life approximately 2.5 hours. Distribution half-life only 7.6 minutes indicates rapid tissue uptake.
PMID:23099431No long-term human data available. Unknown whether tachyphylaxis develops. Theoretical concerns about HPA axis effects and chronic appetite stimulation.
Research-based observations
This timeline reflects observations from published clinical and preclinical studies. Individual responses may vary significantly. This is not a guarantee of effects or a dosing schedule. Consult qualified healthcare providers for personalized guidance.
Good Signs (6 indicators)
Warning Signs (5 indicators)
Bad Signs (6 indicators)
For Research Evaluation Only
These quality indicators are general guidelines based on typical peptide characteristics. Professional laboratory testing (HPLC, mass spectrometry) provides definitive quality verification. This checklist is for initial visual evaluation only.
CJC-1295
SynergisticWell-established GHRH+GHRP synergy. GHRP-6 initiates GH pulse via ghrelin receptor while CJC-1295 amplifies release via GHRH receptor. Greater GH release than either alone.
Sermorelin
SynergisticClassic GHRH+GHRP combination. Sermorelin (GHRH analog) and GHRP-6 act through complementary pathways with synergistic effect on GH secretion.
Ipamorelin
CompatibleBoth are GHRPs acting on ghrelin receptor. Ipamorelin is more selective with cleaner profile. No clear rationale for combining same-mechanism agents.
GHRP-2
CompatibleSame receptor target. GHRP-2 is more potent but both affect cortisol/prolactin. No established benefit to combining.
MK-677
CompatibleBoth stimulate GH via ghrelin pathway. MK-677 provides 24-hour elevation. May be redundant but mechanisms differ slightly.
BPC-157
CompatibleCuban CIGB research explores cytoprotective combinations. Different mechanisms; no known contraindications.
Semaglutide
CautionGHRP-6 strongly stimulates appetite via ghrelin signaling, which may counteract semaglutide's appetite-suppressing effects. Also monitor glucose.
Research Note: Interaction data is based on published literature, mechanistic understanding, and theoretical considerations. Most peptide combinations lack direct clinical study. This information is for educational purposes only and does not constitute medical advice. Always consult qualified healthcare providers.
Key Studies Cited
Full reference list available on request. All citations link to PubMed for verification.
This dossier synthesizes available evidence from peer-reviewed literature, regulatory documents, and clinical trial registries. Evidence strength ratings follow a modified GRADE approach.
For complete methodology details, see our Methodology page.
Important Disclaimer
This dossier is for educational purposes only and does not constitute medical advice. Always consult a qualified healthcare provider before making health decisions.
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Compare GHRP-6
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