All peptides / Muscle and bone
GHRP-6
GHRP / ghrelin agonist
Also GHRP6, GHRP 6, Growth hormone releasing peptide-6, Growth hormone-releasing peptide 6, SKF-110679, His-D-Trp-Ala-Trp-D-Phe-Lys-NH2
- Evidence
- CAnimal and cell studies
- FDA status
- Not approvedas of 2026-10-26
- Route
- Injection
- Studies cited
- 1 human1 animal or cell
A peptide sold to build muscle, burn fat and heal injuries. It raises growth hormone, but no human study has tested muscle, fat or healing.
Sold for
GHRP-6 is sold as a growth hormone releaser for muscle gain, fat loss and injury recovery, and sometimes as an appetite stimulant.
Studies say
GHRP-6 does raise growth hormone and IGF-1 in healthy men over a day and a half of infusion, but there is no human trial measuring muscle, fat or recovery, and the heart findings are from rodents given a related peptide, which is the C grade.
Why grade C. For the muscle and recovery use GHRP-6 is sold for, the cited human evidence is a 1993 study in nine healthy men who received a 34-hour intravenous infusion of GHRP-6 or saline, measuring growth hormone and IGF-1 with no body-composition or health endpoint. The cardiovascular claims rest on rat and mouse heart experiments with hexarelin, a related peptide, and on a review of animal work. 213
FDA. GHRP-6 is not approved by the FDA for any use and is sold online as a research chemical. No company has filed for approval in any indication. 3
Written from 3 cited sources. Fact-checked 2026-10-27: 14 claims checked, 8 corrected. Last refreshed 2026-10-27. Not physician reviewed.
What this means for you
- What people take it for
- Muscle gain, fat loss and recovery
- Can a US doctor prescribe it?
- No. It is not approved and is sold as a research chemical.
- Properly tested in people?
- Not properly: one hormone study of nine men and some animal work.
Evidence checklist
- Randomised controlled trial One 1993 pharmacology studyno
- Human study over 100 people Small study in normal menno
- More than one research group Little independent workno
- Clinical outcomes, not surrogate markers Growth hormone rise onlyno
- Human safety data beyond case reports Only single-dose datano
Drawn from the cited studies below. A dash means the sources give no information.
What it is
GHRP-6 was the first growth hormone-releasing peptide studied extensively in humans, a six-amino-acid synthetic sequence built by Cyril Bowers' group in the early 1980s before anyone knew what receptor it hit. The receptor was cloned in 1996 and its natural ligand, ghrelin, was found in 1999, so GHRP-6 is in effect a ghrelin mimic that predates ghrelin. 32
It shares its receptor and its general effects with GHRP-2, hexarelin and ipamorelin. Later analogs were made to be more potent or more selective; GHRP-6 remained a research tool. 3
How it works
GHRP-6 binds the growth hormone secretagogue receptor (GHS-R1a) on pituitary cells and in the hypothalamus, producing pulses of growth hormone. In a 1993 study, nine healthy young men received a 34-hour intravenous infusion of GHRP-6 or saline; during the GHRP-6 infusion the total amount of growth hormone released roughly doubled, the size of each pulse rose while their number did not, and growth hormone responses to injected GHRH were larger than usual. That synergy with GHRH is why users often combine the two classes. 2
Growth hormone-releasing peptides also bind CD36, a scavenger receptor found on heart muscle and blood-vessel cells. Bodart and colleagues showed in 2002 that hexarelin, a close relative of GHRP-6, raised coronary perfusion pressure in isolated rat and mouse hearts through CD36, an effect absent in hearts lacking CD36; the authors linked it to coronary vasospasm. This line of work, together with animal studies of protection against heart ischemia, is the origin of the "cardioprotective" label attached to GHRP-6 and hexarelin online. 13
What human research shows
The human data in the citation set come from one physiology study: nine healthy men infused with GHRP-6 or saline for 34 hours and sampled for growth hormone. The pituitary stayed responsive throughout, growth hormone output roughly doubled, and IGF-1 rose from 252 to 312 micrograms per litre over the infusion. No trial measured strength, lean mass or recovery from injury. 2
| Study | Model | Finding |
|---|---|---|
| Jaffe 1993, prolonged infusion | Humans, n=9 healthy men, 34-hour intravenous infusion versus saline | Growth hormone output roughly doubled with larger pulses, IGF-1 rose, and responses to GHRH boluses were augmented. 2 |
| Bodart 2002, CD36 | Isolated rat and mouse hearts, CD36-null mice, rat cardiac membranes | Hexarelin raised coronary perfusion pressure through CD36, an effect lost in hearts lacking CD36. 1 |
| Review 2006, GH secretagogues | Narrative review of experimental models | Growth hormone secretagogues act on GHS-R1a and on CD36, with cardiac effects shown in animal models. 3 |
Safety
The 34-hour infusion study reported no serious adverse effects, though thyroid-stimulating hormone was lower during the infusion. The peptide mimics ghrelin, so increased hunger is expected, and users report it with GHRP-6 in particular. Long-term safety in humans has not been studied, and because growth hormone raises blood glucose and IGF-1, the theoretical concerns are insulin resistance and growth of existing tumours. Research-chemical products carry no purity assurance. 32
Questions for your clinician
- Is there any trial showing GHRP-6 builds muscle or heals injuries?
- How would a growth hormone rise affect my blood sugar?
- Are there approved options for my goal?
Questions people ask
Is GHRP-6 FDA-approved?
No. GHRP-6 has never been submitted for approval for any indication and is sold as a research chemical. 3
Does GHRP-6 raise growth hormone in humans?
Yes. In nine healthy men a 34-hour infusion of GHRP-6 roughly doubled growth hormone output and raised IGF-1, and the pituitary did not stop responding. Whether that translates to any change in muscle or fat has not been tested. 2
Is GHRP-6 good for the heart?
That claim comes from animal work showing that growth hormone-releasing peptides act on a cardiac receptor called CD36; in the key study the related peptide hexarelin constricted coronary vessels in rodent hearts. No human cardiac study of GHRP-6 exists. 13
Why does GHRP-6 cause hunger?
It mimics ghrelin, the stomach hormone that drives appetite, by acting on the same receptor. Hunger is the most commonly reported effect of the class. 3
Citations
- Bodart 2002, Circulation Research: CD36 mediates the cardiovascular action of growth hormone-releasing peptides in the heart doi.org
- Jaffe 1993, Journal of Clinical Endocrinology and Metabolism: prolonged GHRP-6 infusion and pulsatile growth hormone secretion in normal men doi.org
- Cao 2006, Trends in Endocrinology and Metabolism: effects of ghrelin and synthetic GH secretagogues on the cardiovascular system doi.org