GHRP-2
A synthetic ghrelin mimetic used clinically in Japan as a diagnostic test for growth hormone deficiency. Reliably raises GH; also raises cortisol and prolactin.
Growth Hormone
GHRP-6
The original growth hormone releasing peptide. Effective at raising GH but produces the strongest appetite stimulation of the class, plus cortisol and prolactin elevation.
Overview
GHRP-6 was the compound that established that a synthetic peptide could trigger growth hormone release through a receptor nobody had identified yet — the receptor for ghrelin was found afterwards, by working backwards from this molecule. It causes a strong GH pulse, but it is also the most powerful appetite stimulant in the group, often producing intense hunger within twenty minutes of injection.
A synthetic hexapeptide (His-D-Trp-Ala-Trp-D-Phe-Lys-NH2) agonist at GHS-R1a. Historically the lead compound whose deorphanisation of the growth hormone secretagogue receptor led to the discovery of ghrelin. Stimulates GH release from somatotrophs and suppresses somatostatin tone; potent orexigenic effect via hypothalamic NPY/AgRP neurons. Also elevates ACTH/cortisol and prolactin. Separately investigated for cytoprotective effects in cardiac and hepatic injury models, an area distinct from its GH activity.
Research areas
Growth hormone axisAppetiteCytoprotection
Dosing reported in the literature
Every protocol below is reproduced from a published study or approved labelling, with its source named. These are records of what was studied — not recommendations, and not a suggestion that any of them is appropriate for any person.
| Protocol as reported | Source |
|---|---|
| Intravenous bolus of 1 mcg/kg with GH sampling over 120 minutes | Bowers et al., Endocrinology 1984 and subsequent human series |
| Intranasal administration in early human GH-release studiesBioavailability by this route is low and variable. | Early GHRP-6 pharmacodynamic literature |
Trial status
Short-term human pharmacodynamic studies only. No completed efficacy trials for body composition or any clinical endpoint.
Reported safety signals
- Marked appetite stimulation is the most consistently reported effect and is often the limiting factor in practice.
- Raises cortisol and prolactin along with growth hormone.
- No chronic human safety data at any dose or duration.
- Sold entirely through unregulated research-chemical channels.
Common questions
Why is GHRP-6 historically important?
It was the synthetic compound whose activity implied the existence of a receptor nobody had found. Tracing that receptor led directly to the discovery of ghrelin in 1999 — the hormone was found because the drug came first.
Primary sources
Medical disclaimer
This page is for informational and research purposes only. Nothing here constitutes medical advice. The compounds discussed are research chemicals. Consult a qualified clinician before starting any protocol.
How this profile was built →