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.
Growth Hormone
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.
Overview
GHRP-2 acts on the same pituitary receptor as ghrelin, the hunger hormone. Activating it triggers a sharp release of growth hormone, and it works through a different route than GHRH analogues like sermorelin — which is why the two are often combined. The catch is that the receptor is not perfectly selective in its downstream effects: GHRP-2 also nudges cortisol and prolactin upward, and it stimulates appetite.
A synthetic hexapeptide agonist at the growth hormone secretagogue receptor GHS-R1a. Acts on pituitary somatotrophs and hypothalamic neurons, amplifying GH release both directly and by suppressing somatostatin tone, producing synergy with GHRH analogues. Also produces modest ACTH/cortisol and prolactin elevation through the same receptor family. Approved in Japan as pralmorelin for GH-deficiency diagnostic testing. Chronic administration data in humans is limited and there is no completed efficacy programme for body composition endpoints.
Research areas
Growth hormone axisGH deficiency diagnosisAppetite
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 |
|---|---|
| 100 mcg intravenous bolus with GH sampling over 60 minutes as a GH-deficiency provocation test | Japanese pralmorelin diagnostic protocol |
| Subcutaneous doses of 1 mcg/kg in pharmacodynamic studies of GH release | Bowers et al., Journal of Clinical Endocrinology & Metabolism 1990s series |
Trial status
Diagnostic approval in Japan. Human studies are largely short-term pharmacodynamic work; no long-term efficacy programme.
Reported safety signals
- Raises cortisol and prolactin alongside growth hormone, unlike GHRH analogues.
- Stimulates appetite substantially — this is a mechanistic effect, not an incidental one.
- Chronic use has not been studied for safety in humans at any duration relevant to how it is used non-medically.
- Water retention, numbness and tingling are reported with sustained GH elevation.
Common questions
How is GHRP-2 different from ipamorelin?
Both hit the same receptor, but ipamorelin is markedly more selective — it raises growth hormone with little or no effect on cortisol, prolactin or appetite. GHRP-2 raises all of them. That selectivity difference is the main reason ipamorelin displaced the older GHRPs in practice.
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.
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