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What Is GHRP-6?
GHRP-6 (Growth Hormone Releasing Peptide-6) is a synthetic hexapeptide that stimulates growth hormone release by acting on the ghrelin receptor (GHS-R1a). It was one of the first GH secretagogues developed and remains one of the most potent at stimulating GH release.
GHRP-6 is known for producing robust GH release but also significant increases in appetite (hunger), cortisol, and prolactin — distinguishing it from more selective peptides like ipamorelin.
Key Characteristics
- GH Release: Very potent
- Appetite: Strong hunger stimulation
- Cortisol: Moderate increase
- Prolactin: Moderate increase
Mechanism of Action
Ghrelin Receptor Activation
GHRP-6 mimics ghrelin, the "hunger hormone":
- Binds to and activates ghrelin receptors (GHS-R1a)
- Stimulates GH release from pituitary somatotrophs
- Also acts on hypothalamic neurons
- Triggers appetite through ghrelin-like effects
Multi-Hormone Effects
Unlike more selective GHRPs, GHRP-6 affects multiple hormones:
- Growth Hormone: Strong release
- Cortisol: Notable increase (~30%)
- Prolactin: Moderate elevation
- Ghrelin: Mimics effects (hunger, gastric motility)
Synergy with GHRH
GHRP-6 works synergistically with GHRH analogs:
- Different receptor pathways (ghrelin vs GHRH)
- Combined effect greater than sum of parts
- Can amplify GH release 3-5 fold when combined
Research Findings
Growth Hormone Release
- Produces reliable, dose-dependent GH release
- Peak GH levels within 15-30 minutes
- Duration of effect: 3-4 hours
- Response maintained with repeated dosing
Appetite Stimulation
The most notable "side effect" of GHRP-6:
- Strong hunger sensation 20-30 minutes post-injection
- Mediated through ghrelin receptor in hypothalamus
- Can be beneficial for those seeking weight gain
- Problematic for those seeking fat loss
Cardioprotective Research
Interesting research suggests cardioprotective effects:
- Reduced cardiac damage in ischemia models
- May protect against myocardial infarction
- Anti-fibrotic effects in heart tissue
- These effects may be independent of GH release
Gastric Effects
- Increases gastric motility (like ghrelin)
- May improve gut healing in some models
- Protective effects against certain GI stressors
Key Published Research
| Year | Focus | Key Finding | Reference |
|---|---|---|---|
| 1995 | GH release | Characterized dose-response | Bowers et al. |
| 2003 | Cardioprotection | Reduced infarct size in rats | Gonzalez et al. |
| 2007 | Synergy with GHRH | Amplified GH release | Alvarez et al. |
| 2012 | Anti-fibrotic | Cardiac remodeling effects | Berlanga et al. |
Comparison with Other GHRPs
| Peptide | GH Release | Hunger | Cortisol | Prolactin |
|---|---|---|---|---|
| GHRP-6 | ++++ | ++++ | ++ | ++ |
| GHRP-2 | ++++ | ++ | ++ | +++ |
| Ipamorelin | +++ | + | - | - |
| Hexarelin | +++++ | + | +++ | +++ |
Potential Applications
Research Areas
- Weight Gain: Appetite stimulation + GH anabolic effects
- Muscle Building: Combined anabolic signaling
- Cardioprotection: Heart tissue protection research
- GH Deficiency: Diagnostic and potential therapeutic
- Gut Health: Gastric motility and protection
Administration in Research
- Route: Subcutaneous or intravenous
- Research doses: 100-300 mcg per injection
- Frequency: 2-3 times daily
- Timing: Pre-meal (amplifies hunger) or before bed
- Half-life: ~15-20 minutes
Side Effects and Considerations
- Intense hunger: Most reported effect
- Water retention: Possible, especially initially
- Cortisol elevation: May affect sleep if dosed at night
- Prolactin increase: Generally not problematic at standard doses
- Tingling/numbness: Transient, usually at injection site
Research Status
GHRP-6 is not approved by the FDA for any indication. It is available only as a research compound. The significant appetite stimulation and cortisol effects make it less popular than more selective alternatives like ipamorelin for many research applications.
Summary
GHRP-6 remains one of the most potent growth hormone releasing peptides available for research. Its strong appetite stimulation — while a drawback for some applications — can be beneficial for research into weight gain and muscle building. The cardioprotective research adds an interesting dimension beyond GH release. However, its effects on cortisol and prolactin have led many researchers to prefer more selective alternatives like ipamorelin.