GHRP-6: What the Research Actually Shows
- What it is: A synthetic six-amino-acid peptide, growth hormone-releasing peptide 6, first described in 1984. It binds the ghrelin receptor on the pituitary.
- Research areas: growth hormone release in pituitary cells and animals, the receptor that led to the discovery of ghrelin, feeding behavior in rats, and heart tissue in animal injury models.
- Evidence level: Decades of cell and animal work. The human data we found is small, short studies of hormone release.
- The short version: GHRP-6 was designed before its receptor was known. Cloning that receptor in 1996, and finding its natural partner ghrelin in 1999, is the reason the compound still matters. In the studies that measured them, growth hormone rose, and so did cortisol and prolactin.
GHRP-6 (growth hormone-releasing peptide 6) is a synthetic six-amino-acid peptide, His-D-Trp-Ala-Trp-D-Phe-Lys-NH2, that triggers growth hormone release from the pituitary by binding the ghrelin receptor, GHS-R1a. It was first described in 1984, years before that receptor or ghrelin itself had been identified, and much of what is known about the ghrelin pathway was worked out with it.
Below is what the studies looked at, in what kind of model, and what they reported. This is a summary of published research, not a description of what the compound does in a person.
Not in the shop. GHRP-6 is not part of the Etched Research retail catalog. This page is a research summary only. The compounds Etched Research does carry are listed in the shop.
Quick facts
- Names: GHRP-6, growth hormone-releasing peptide 6, [His1,Lys6]-GHRP in the first paper, SKF 110679 as a code name.
- Sequence: His-D-Trp-Ala-Trp-D-Phe-Lys-NH2, six amino acids, two of them in the D form, with an amidated end (Bowers et al., 1984).
- Molecular formula C46H56N12O6, molecular weight 873.0 g/mol, CAS 87616-84-0 (PubChem CID 9919153).
- Class: a growth hormone secretagogue and ghrelin receptor agonist. It is not growth hormone, and not a GHRH analog.
- Relatives: hexarelin is GHRP-6 with one change, a methyl group on the D-tryptophan at position 2. Ipamorelin came out of a later chemistry program built on the same family.
- Approval status: GHRP-6 is not an approved drug in the United States, and the FDA’s Drugs@FDA database lists no product containing it.
What the research found
Most of the record is pituitary cells and animals. The human work is a short list of hormone-release studies. Results are listed as the authors reported them.
The first description (Bowers, Endocrinology, 1984). The Tulane group reported a new synthetic hexapeptide that released growth hormone from rat pituitary cells and in rats, monkeys, lambs and calves, without releasing LH, FSH, TSH or prolactin in those experiments. Two forms of somatostatin blocked the response, and the pituitary stayed responsive after repeated exposure. The authors proposed it as a tool for studying the pituitary’s growth hormone cells. Cells and animals. PMID 6714155.
The first human study (Bowers, Journal of Clinical Endocrinology and Metabolism, 1990). Eighteen healthy men received GHRP-6 at three dose levels, GHRH alone, and the two in combination, with placebo for comparison. Growth hormone rose with the GHRP-6 dose. At the highest dose tested, prolactin and cortisol roughly doubled from baseline, while LH and TSH did not change. When the two were combined, growth hormone release was greater than either produced alone, which the authors read as a sign that GHRP-6 and GHRH act through separate systems. Short-term, single-session. PMID 2108187.
The receptor is found (Howard, Science, 1996). A Merck team cloned a G protein-coupled receptor from the pituitary and hypothalamus of pigs and humans and showed it was the target of the synthetic growth hormone secretagogues, the class GHRP-6 belongs to. They concluded these compounds were imitating a hormone nobody had found yet. PMID 8688086.
The natural partner is found (Kojima, Nature, 1999). Researchers purified the receptor’s own ligand from rat stomach, a 28-amino-acid peptide with a fatty acid attached at serine 3, and named it ghrelin. It released growth hormone in cells and in animals. This is the hormone GHRP-6 had been mimicking for fifteen years. PMID 10604470.
Feeding behavior (Locke, Life Sciences, 1995). In sated adult male rats, GHRP-6 delivered into the brain’s ventricles increased the incidence of eating in a dose-related way, while blood growth hormone did not track the dose. The authors concluded the feeding effect ran through a mechanism separate from growth hormone release. Rats. PMID 8614257.
The selectivity comparison (Raun, European Journal of Endocrinology, 1998). The study that introduced ipamorelin used GHRP-6 as its benchmark. In rat pituitary cells, rats and pigs, the two released growth hormone with similar potency. In pigs, GHRP-6 and GHRP-2 both raised ACTH and cortisol, and ipamorelin did not beyond the levels seen with GHRH. Cells and animals. PMID 9849822.
Heart tissue in an injury model (Berlanga, Clinical Science, 2007). A Havana group randomized pigs with a surgically blocked coronary artery to GHRP-6 or saline. The GHRP-6 group had smaller areas of damaged heart muscle and lower oxidative stress markers, with no change in deaths during surgery. The authors attributed part of the effect to antioxidant activity. Pigs. PMID 16989643.
The cytoprotection review (Berlanga-Acosta, Clinical Medicine Insights: Cardiology, 2017). The same group reviewed work on the GHRP family since the 1980s. They describe two receptors, GHS-R1a and a second one, CD36, and summarize preclinical studies in heart, nerve, gut and liver cells that they read as evidence of cell protection. They also note that, after decades of research, the family has no established clinical use. Review, written by the group behind much of the work it reviews. PMID 28469491.
How it works
Growth hormone leaves the pituitary in pulses, and two separate signals act on the cells that release it. One is GHRH, a hormone from the hypothalamus. The other is the ghrelin receptor, GHS-R1a, which GHRP-6 binds. The 1990 human study is a large part of why researchers treat these as two separate systems (Bowers et al., 1990).
The ghrelin receptor is not only on the pituitary. The 1996 cloning study also found it in the hypothalamus (Howard et al., 1996), and the 1995 rat study concluded that the feeding effect it saw ran through a mechanism separate from growth hormone release (Locke et al., 1995). For the heart work, the 2017 review names a second receptor, CD36, which researchers have also examined for hexarelin (Berlanga-Acosta et al., 2017).
What the research does not establish
- The human studies we found are small, short and measured hormone levels. None of them was a long-term trial.
- GHRP-6 is not selective for growth hormone. Cortisol and prolactin rose in the human study, and ACTH and cortisol rose in pigs.
- The feeding and heart findings come from rats and pigs. They describe what happened in a research model, not what would happen in a person.
- Much of the heart and cytoprotection literature comes from one research group.
- Nothing here is a safety conclusion, and this is not a claim that the compound is safe to use.
Common questions
What is GHRP-6?
GHRP-6 is a synthetic six-amino-acid peptide, His-D-Trp-Ala-Trp-D-Phe-Lys-NH2, first described in 1984 as a compound that releases growth hormone from the pituitary (Bowers et al., 1984). It acts at the ghrelin receptor, GHS-R1a. It is not growth hormone itself.
How is GHRP-6 related to ghrelin?
GHRP-6 came first, and ghrelin was found by following it. A 1996 study cloned the receptor that GHRP-6 and related compounds act on (Howard et al., 1996), and in 1999 researchers isolated the body’s own ligand for that receptor from rat stomach and named it ghrelin (Kojima et al., 1999).
What is the difference between GHRP-6 and ipamorelin?
In the 1998 study that introduced ipamorelin, GHRP-6 raised ACTH and cortisol in pigs and ipamorelin did not, although the two released growth hormone with similar potency (Raun et al., 1998). Both bind the ghrelin receptor. Ipamorelin is five amino acids and GHRP-6 is six. More on the newer compound is in the ipamorelin research summary.
Has GHRP-6 been studied in people?
The human studies we found are small, short-term studies of hormone release. The first, in 18 healthy men, measured a rise in growth hormone and, at the highest dose tested, in prolactin and cortisol as well (Bowers et al., 1990). We did not find a long-term controlled trial.
Is GHRP-6 in the Etched Research shop?
No. GHRP-6 is not part of the Etched Research retail catalog. This page is in the research library because the compound is part of growth hormone axis research, and the library covers more compounds than the shop does.
More in this research area: Growth Hormone Signaling Research | Research Library
Last reviewed 2026-10-03.
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