GHRP-6 Peptide
Research Guide

What is GHRP-6?

GHRP-6 (growth hormone releasing peptide 6, also written GHRP 6) is a synthetic hexapeptide, His-D-Trp-Ala-Trp-D-Phe-Lys-NH2. Bowers and colleagues described it in 1984 as a small peptide that acts on the pituitary to release growth hormone (GH) without releasing LH, FSH, TSH or prolactin (Bowers et al., 1984). It works through a receptor separate from the GH releasing hormone (GHRH) receptor (Cheng et al., 1989).

That receptor, GHS-R1a, is now usually called the ghrelin receptor, after its natural ligand was found in the stomach (Kojima et al., 1999). Disguised Alpha does not currently list GHRP-6; this page is a literature reference for laboratory researchers. Nothing on this page is guidance for use in people.

GHRP-6 reference data

Sequence, formula, weight and aliases are from PubChem CID 9919153, the record with all six stereocenters defined; the class follows the receptor literature below. A PubChem name search for "GHRP-6" returns CID 4345065, with the same formula and weight but no stereocenters defined. The acetate salt has its own record (CID 72941687, 1053.2 g/mol as the triacetate).

See it beside the other compounds on this site in the peptide molecular weight reference table.

What the research covers

Published work on GHRP-6 falls into five areas, each naming its model. Much of the tissue-protection work and the recent human trials come from one Havana institute, the Center for Genetic Engineering and Biotechnology.

Discovery and GH release in animals

The 1984 paper reported GH release in a pituitary incubation assay and in rats, monkeys, lambs and calves. After intravenous delivery in rats, GH rose within 2 minutes, peaked at 10 to 20 minutes and usually returned to baseline by 2 hours, and somatostatin inhibited the response (Bowers et al., 1984). In conscious swine, GHRP-6 released GH with an ED50 of 3.9 nmol/kg and also raised ACTH and cortisol (Raun et al., 1998). Models: pituitary tissue and five animal species.

Pituitary mechanism and the ghrelin receptor

In rat primary pituitary cells, GHRP-6 released GH with a half-maximal effect at 7 nM. A GHRH receptor antagonist did not block it, it did not raise cyclic AMP while GHRH tripled it, and the two together acted synergistically. An analog with D-lysine at position 3, the antagonist usually written [D-Lys3]-GHRP-6, inhibited GHRP-6 without affecting GHRH (Cheng et al., 1989).

In pig and rat pituitary membranes, one high-affinity binding site, not displaced by GHRH or somatostatin, mediated the activity of GHRP-6 and of non-peptide secretagogues such as MK-0677 (Pong et al., 1996). Its natural ligand is ghrelin, a 28-amino-acid peptide with an octanoyl group on serine 3 (Kojima et al., 1999), and cryo-electron microscopy structures show the Gq-coupled receptor bound to ghrelin and to GHRP-6 (Wang et al., 2021). Models: rat and pig pituitary preparations, purified receptor complexes.

Appetite and gastric effects in rats

Delivered into the brain ventricles of rats, GHRP-6 and ghrelin each raised food intake, and an NPY Y1 receptor antagonist blocked both responses. GHRP-6 activated the arcuate, paraventricular and dorsomedial nuclei, orexin neurons of the lateral hypothalamus and two brainstem regions, with the same pattern whether or not the rats could eat (Lawrence et al., 2002). In male Wistar rats under water immersion restraint stress, GHRP-6 given intraperitoneally 2 hours earlier prevented gastric mucosal lesions, while delivery into the brain ventricles did not, suggesting a peripheral site of protection (Guo et al., 2012). Model: rats.

Heart and tissue protection models

In anesthetized pigs given a 1-hour coronary artery occlusion and 72 hours of reperfusion, GHRP-6 reduced infarct mass by 78% and infarct thickness by 50% against saline, lowered CK-MB and C-reactive protein, and preserved antioxidant defenses (Berlanga et al., 2007).

In dogs with pacing-induced dilated cardiomyopathy, none of the eight given GHRP-6 died during acute coronary occlusion, against survival of 57% with GH and 55% with vehicle, which the Merck authors linked to secretagogue receptors, not the GH and IGF-1 pathway (Shen et al., 2003). In rats given doxorubicin, GHRP-6 given alongside prevented ventricular dilation, preserved left ventricular systolic function and raised expression of the prosurvival gene Bcl-2 (Berlanga-Acosta et al., 2024). Models: pigs, dogs and rats (animal data only).

Human research history

In 18 normal men, three ascending intravenous amounts raised mean peak GH from 1.2 µg/L after placebo to 68.7 µg/L at the highest amount. Prolactin and cortisol rose about two fold only at that amount, and lower amounts combined with GHRH released GH synergistically (Bowers et al., 1990).

As a diagnostic test given with GHRH, it distinguished 125 healthy controls (mean peak GH 59.2 µg/L) from 125 adults with pituitary disease and severe GH deficiency (4.1 µg/L) (Popovic et al., 2000). A phase I study in nine healthy men reported a distribution half-life of 7.6 minutes and an elimination half-life of 2.5 hours (Cabrales et al., 2013).

In an open-label phase III trial, 188 adults with acute ischemic stroke were randomized to a week of intravenous epidermal growth factor plus GHRP-6 or to standard care. It missed its primary endpoint (disability), and daily function and survival also did not differ overall.

Severe adverse events occurred in 30 of 95 on the combination and 18 of 93 on standard care, none judged related to the study drugs. In a severe-stroke subgroup of 27, those on the combination had less disability at six months than controls, and the authors called for studies in moderate to severe stroke (Hernández-Bernal et al., 2026).

Key studies

1. Bowers CY, et al. "On the in vitro and in vivo activity of a new synthetic hexapeptide that acts on the pituitary to specifically release growth hormone." Endocrinology. 1984. PMID 6714155. DOI 10.1210/endo-114-5-1537. Pituitary incubations and several species: selective GH release in vitro and in vivo.
2. Bowers CY, et al. "Growth hormone (GH)-releasing peptide stimulates GH release in normal men and acts synergistically with GH-releasing hormone." J Clin Endocrinol Metab. 1990. PMID 2108187. DOI 10.1210/jcem-70-4-975. 18 normal men, ascending amounts against placebo: GH, prolactin and cortisol responses.
3. Lawrence CB, et al. "Acute central ghrelin and GH secretagogues induce feeding and activate brain appetite centers." Endocrinology. 2002. PMID 11751604. DOI 10.1210/endo.143.1.8561. Rats, central delivery: feeding blocked by an NPY Y1 antagonist, with c-Fos mapping.
4. Berlanga J, et al. "Growth-hormone-releasing peptide 6 (GHRP6) prevents oxidant cytotoxicity and reduces myocardial necrosis in a model of acute myocardial infarction." Clin Sci (Lond). 2007. PMID 16989643. DOI 10.1042/CS20060103. Pigs with a 1-hour coronary occlusion, randomized to GHRP-6 or saline: smaller infarcts.
5. Hernández-Bernal F, et al. "Phase III Open-Label, Randomized Clinical Trial of Epidermal Growth Factor and Growth Hormone Releasing Hexapeptide in Acute Ischemic Stroke." J Clin Neurosci. 2026. PMID 42462342. DOI 10.1016/j.jocn.2026.112195. 188 adults with stroke, randomized and open-label: primary endpoint missed.

Handling and storage of lyophilized GHRP-6

GHRP-6 is usually handled as a lyophilized (freeze-dried) powder. General laboratory practice, covered in the peptide storage guide and the peptide reconstitution guide:

• Keep the sealed powder dry, frozen and protected from light; its two tryptophans are prone to oxidation.
• Let a sealed vial reach room temperature before opening, add diluent slowly down the wall, swirl rather than shake, and split stock into single-use aliquots for storage at 2 to 8°C.
• The sequence has no acidic residues and three basic groups (amino terminus, histidine, lysine), so it behaves as a basic peptide when choosing a diluent.
• Heated in the dark at 60°C across pH 3 to 8, GHRP-6 deamidated at the C-terminus mainly at pH 3 and 8, hydrolyzed and cyclized at pH 6 to 7 in phosphate buffers, took up acyl groups from carboxylic acid buffers, and formed a product likely from formaldehyde released by additives or rubber closures (Santana et al., 2021).
• Record the lot number, base molarity on the form the certificate names (free peptide or acetate salt), and confirm identity by mass (monoisotopic 872.44 Da).

Frequently asked questions

What is GHRP-6?

GHRP-6 is a synthetic six-amino-acid peptide that releases growth hormone by acting at the ghrelin receptor, GHS-R1a. It was first characterized in 1984 (Bowers et al., 1984), and a 2021 cryo-EM study solved the receptor bound to it (Wang et al., 2021).

Is GHRP-6 a peptide?

Yes. The GHRP-6 peptide is a chain of six amino acids, two of them in the D configuration. It is not ghrelin, the natural ligand of the same receptor (Kojima et al., 1999), and it is not [D-Lys3]-GHRP-6, an analog that inhibits its GH response (Cheng et al., 1989).

How is GHRP-6 different from ipamorelin?

Both act at the ghrelin receptor. In conscious swine, ipamorelin, a pentapeptide, released GH much like GHRP-6 but did not raise ACTH or cortisol beyond the levels seen with GHRH, while GHRP-6 raised both (Raun et al., 1998). The ipamorelin research guide covers it in full.

Does GHRP-6 change food intake in studies?

In rats, yes, as a measured endpoint after delivery into the brain ventricles (Lawrence et al., 2002). A PubMed search on 11 October 2026 found no controlled human food-intake study of GHRP-6.

Is GHRP-6 prohibited in sport?

Yes. The 2026 WADA Prohibited List names GHRP-6 among the GH-releasing peptides in section S2.2.4 (growth hormone releasing factors) of class S2, prohibited at all times, in and out of competition. The FDA also lists GHRP-6 in category 2 for section 503B compounding, its list of bulk drug substances that may present significant safety risks, citing a possible immunogenicity risk for certain routes and safety concerns in limited data, including a potential effect on cortisol and increased blood glucose from decreased insulin sensitivity.

Does Disguised Alpha sell GHRP-6?

Not currently. Two related compounds that act at the same receptor are in the catalog: ipamorelin (ipamorelin research guide) and MK-677, also called ibutamoren (MK-677 research guide). The growth hormone secretagogues guide covers the wider family.

Related compounds and guides

• Ipamorelin research guide
• MK-677 (Ibutamoren) research guide
• Growth hormone secretagogues explained
• MK-677 vs ipamorelin: research comparison
• Peptide storage guide and peptide reconstitution guide

All Disguised Alpha products are for laboratory research only and are not for human consumption.

Research basics

• What are peptides?
• What is a certificate of analysis (COA)?
• What does lyophilized mean?
• What are peptide bioregulators?
• Peptide calculator: concentration and volume
• Peptide molecular weight calculator