GHRP-6
Growth Hormone Releasing Peptide-6
Also known as: GHRP-6, Growth Hormone Releasing Hexapeptide, SKF-110679
Prompted by Jack Butcher (Visualize Value) · AI-authored by Claude · Research-sourced
A potent GH secretagogue that produces strong growth hormone pulses and intense appetite stimulation through ghrelin receptor activation. Best combined with GHRH analogs for synergistic release.
Quick Facts
Not FDA-approved for human use. Research compound only.
Overview
GHRP-6 is a synthetic hexapeptide that stimulates growth hormone release by mimicking the action of ghrelin at the growth hormone secretagogue receptor (GHS-R1a). It was one of the first synthetic GH secretagogues developed and has been widely studied since the early 1990s.
GHRP-6 is known for producing robust GH pulses and is notable for its strong appetite-stimulating effects — a feature that distinguishes it from more selective secretagogues like Ipamorelin. This hunger response is directly mediated through the ghrelin receptor.
While effective at elevating GH and IGF-1 levels, GHRP-6 is considered less selective than newer peptides because it also increases cortisol and prolactin to a modest degree.
Mechanism of Action
GHRP-6 binds to the growth hormone secretagogue receptor (GHS-R1a), the same receptor targeted by the endogenous hormone ghrelin. Activation of this receptor in the anterior pituitary stimulates GH release through a phospholipase C and IP3/DAG signaling cascade.
Unlike GHRH analogs (e.g., CJC-1295), which amplify GH pulse amplitude, GHRP-6 initiates new GH pulses. When combined with GHRH analogs, the two pathways produce a synergistic GH release significantly greater than either alone.
GHRP-6 also suppresses somatostatin, the hormone that inhibits GH release, further amplifying the GH response. Its activation of the ghrelin receptor in the hypothalamus and gut directly stimulates appetite through NPY/AgRP neuron activation.
Research Summary
GHRP-6 has been studied in human clinical trials demonstrating reliable GH release. A study in healthy volunteers showed a 3-6 fold increase in GH levels within 15-30 minutes of subcutaneous administration.
Research on GH secretagogue combinations shows that GHRP-6 combined with GHRH produces a synergistic GH response approximately 10-fold greater than GHRP-6 alone. This synergy forms the basis for common combination protocols.
Cardioprotective research shows GHRP-6 has cytoprotective effects on cardiac tissue. Studies in ischemia-reperfusion models demonstrate reduced infarct size and improved cardiac function, mediated through a pathway independent of GH release.
Animal studies demonstrate improvements in body composition with chronic GHRP-6 administration, including increased lean mass and reduced adiposity, though these effects are primarily mediated through elevated GH/IGF-1.
Key References
Growth hormone-releasing peptide-6 stimulates GH release in humans
Bowers CY, et al. · Journal of Clinical Endocrinology & Metabolism (1990) · 10.1210/jcem-70-4-975
Foundational study demonstrating GHRP-6 stimulates significant GH release in humans via subcutaneous and intravenous routes.
Synergistic interaction between GHRH and GHRP-6 on GH release in man
Bowers CY, et al. · Journal of Clinical Endocrinology & Metabolism (1984)
Demonstrated the synergistic GH release when GHRP-6 is combined with GHRH, producing approximately 10x the GH response of either peptide alone.
Cardioprotective effect of growth hormone-releasing peptide 6 (GHRP-6) in the setting of myocardial ischemia-reperfusion
Berlanga J, et al. · Life Sciences (2007) · 10.1016/j.lfs.2007.06.004
Showed GHRP-6 has direct cardioprotective effects in ischemia-reperfusion injury, reducing infarct size through GH-independent mechanisms.
Protocols
GH release (standard)
Best administered on an empty stomach. GH release is blunted by food, especially carbohydrates and fats. Wait 20–30 min after injection before eating.
Combined with GHRH analog
Synergistic protocol. Administer both peptides simultaneously. The combination produces significantly greater GH release than either alone.
Side Effects & Safety
| Frequency | Effect |
|---|---|
| common | Intense hunger Strong appetite stimulation within 20 minutes of injection. Directly mediated by ghrelin receptor activation. |
| common | Water retention Mild fluid retention, particularly in hands and feet. Typically resolves over weeks. |
| uncommon | Cortisol elevation Modest, transient cortisol increase post-injection. Less selective than Ipamorelin. |
| common | Injection site irritation |
| uncommon | Tingling or numbness Transient paresthesia in extremities shortly after injection. |
Contraindications
- —Active cancer or history of cancer (GH/IGF-1 elevation)
- —Pregnancy or breastfeeding
- —Diabetic retinopathy (GH can worsen)
- —Active pituitary tumors
Reconstitution & Storage
Related Peptides
GHRP-6 is most effective when combined with a GHRH analog like CJC-1295 (no DAC). Ipamorelin is often preferred over GHRP-6 for those who want GH release without the intense hunger.