GHRP-6

Origin and structure

GHRP-6 (growth hormone-releasing peptide 6) is a chain of six amino acids, His-D-Trp-Ala-Trp-D-Phe-Lys-NH2, two of them in the mirror-image D form that the body does not use in its own proteins. The American endocrinologist Cyril Bowers arrived at it through work on modified enkephalin peptides, and his group at Tulane University in New Orleans described it in 1984. It released growth hormone from pituitary cells in the test tube and in rats, monkeys, lambs and calves without releasing other pituitary hormones, and daily injections speeded up weight gain in young rats.

It was one of the first synthetic peptides shown to release growth hormone in living animals as well as in the test tube, and work with it and its successors led to the discovery in 1999 of ghrelin, the 28-amino-acid stomach hormone that naturally activates the same receptor. GHRP-6 itself never became a marketed medicine. Much of the recent research comes from the Center for Genetic Engineering and Biotechnology (CIGB) in Havana, which develops it as a cell-protecting drug candidate. Products sold as GHRP-6 acetate contain the same peptide as its acetate salt.

How it works

GHRP-6 activates the growth hormone secretagogue receptor (GHS-R1a), the receptor that ghrelin also uses, in the pituitary and the hypothalamus. It works through a different route from the body's own growth hormone-releasing hormone (GHRH), which is why the two together release far more growth hormone than either alone: in healthy men, submaximal doses of GHRP-6 acted synergistically with GHRH. One proposed explanation is that GHRP-6 acts as a functional antagonist of somatostatin, the hypothalamic hormone that inhibits growth hormone release.

It is less selective than its name suggests. At 1 µg per kg intravenously, prolactin and cortisol roughly doubled, and repeated night-time doses raised ACTH and cortisol. It also drives eating: injected into the brain of rats that had just eaten, it made them start eating again, independently of its effect on growth hormone. A second binding site, CD36, is the basis of the Cuban work on protecting the heart and other organs, which so far has been done in animals and cells.

It does not stay in the blood for long. In nine healthy men given 100 to 400 µg per kg intravenously, levels fell in two phases, with half-lives of about 8 minutes and 2.5 hours. Routes other than a vein need far larger doses. In a sleep study that compared routes in young men, 300 µg per kg by mouth in enteric-coated capsules left night-time growth hormone unchanged, whereas 30 µg per kg given into the nose raised it.

Is GHRP-6 approved?

No. No medicines regulator in the EU or the US has authorised it, and we found no approval anywhere else. The EMA's database of authorised medicines has no entry for it, and the Dutch medicines register, the Geneesmiddeleninformatiebank, lists no product containing it. In the Netherlands it may therefore not be sold or promoted for use in people; it is available only as research material, which is the basis on which our shop sells it.

In the United States it has never been approved. On 29 September 2023 the FDA placed it in category 2 of its policy for outsourcing facilities (section 503B), for substances that may pose significant safety risks. The agency cited possible immune reactions caused by aggregation and peptide impurities, a possible effect on cortisol, and higher blood glucose through reduced insulin sensitivity. On the FDA's page as updated in April 2026, other peptides such as BPC-157 and CJC-1295 sit on a separate list of withdrawn nominations, but GHRP-6 is still in category 2. For ordinary pharmacies (section 503A), the FDA's list of May 2026 puts it in category 3, substances nominated without adequate support, which the interim policy that lets pharmacies compound substances under evaluation does not cover.

In Cuba it is still an investigational product: its developer's phase 3 trial in stroke, published in 2026, missed its primary endpoint.

In sport it is prohibited at all times. The 2026 WADA Prohibited List names GHRP-6 in class S2.2.4, growth hormone-releasing factors, alongside GHRP-2, hexarelin and ipamorelin. The Netherlands published this list in the Tractatenblad in March 2026, and the Dutch anti-doping rules apply it.

What the research shows

Almost all human data on GHRP-6 come from short studies, mostly from the 1990s and 2000s, that measured hormone levels after a single dose or an infusion of a day or two. They show that it reliably releases growth hormone, not that it improves any health outcome. The Cuban stroke trials are the only ones that tested a clinical result, and they gave GHRP-6 together with another growth factor, EGF. The main studies:

• Healthy men (Bowers et al., 1990): 18 men received intravenous doses of 0.1, 0.3 and 1 µg per kg. Peak growth hormone was 7.6, 16.5 and 68.7 µg/L, against 1.2 µg/L after placebo; at the top dose prolactin and cortisol roughly doubled. No adverse clinical effects or laboratory abnormalities were seen.
• 34-hour infusion (Jaffe et al., 1993): in 9 healthy young men, a continuous infusion roughly doubled total growth hormone release compared with saline, and IGF-1 rose from 252 to 312 µg/L. The pituitary stayed responsive throughout.
• Routes compared (Frieboes et al., 1999): in young men, 300 µg per kg by mouth left night-time growth hormone unchanged, while 30 µg per kg given into the nose raised it; the nasal dose changed sleep only as a trend.
• Diagnostic test (Popovic et al., Lancet 2000): 125 adults with pituitary disease and 125 healthy controls received GHRP-6 and GHRH, 1 µg per kg each, intravenously. Mean peaks were 59.2 µg/L in controls and 4.1 µg/L in patients, with no side effects reported, and the authors proposed 15 µg/L as the cut-off for growth hormone deficiency.
• Stroke, phase 3 (COURAGE-2, published 2026): 188 patients in Cuba within 12 hours of an ischaemic stroke were randomised, without blinding, to EGF plus GHRP-6 intravenously twice daily for 7 days or to standard care. There was no difference in disability, daily functioning or survival, so the trial missed its primary endpoint. In a subgroup of 27 patients with severe stroke the treated group did better, a finding that needs confirmation.
• Heart and organ protection: animal and cell studies, reviewed in 2017 by the Cuban developer's own group, report protection of heart, nerve, gut and liver cells after injury. We found no peer-reviewed trial in heart patients.
• Muscle, fat loss, recovery and anti-ageing: no controlled human trial. The nearest finding is faster weight gain in young rats in the 1984 study.

Hunger, hormones and side effects

Online, GHRP-6 is best known for causing hunger. The direct evidence comes from animals: injected into the brain of rats it triggered eating regardless of its effect on growth hormone, and it acts on the receptor of ghrelin, the body's hunger hormone. We found no published study that measured hunger or food intake in people given GHRP-6, so how strong the effect is in humans, and at which doses, is not known.

The hormone effects are better documented. Cortisol and prolactin rise at higher doses, and the FDA lists an effect on cortisol and higher blood glucose through reduced insulin sensitivity among its safety concerns. Single intravenous doses were well tolerated in the test studies; in the diagnostic study of 250 people no side effects were reported.

In the published studies we found, nobody received GHRP-6 for longer than seven days. In the phase 3 stroke trial, serious adverse events occurred in 30 of 95 treated patients and 18 of 93 controls (odds ratio 1.92, 95% CI 0.98 to 3.77, not statistically significant), and the investigators judged none of them to be caused by the treatment. Repeated injections over weeks or months, as described in community protocols, have never been studied, so their effects on blood sugar, hormones and long-term health are unknown.

Frequently asked questions

Is GHRP-6 legal in the Netherlands?

It is not a registered medicine in the Netherlands or anywhere else in the EU, so it may not be sold, advertised or supplied for use in people. Buying and selling it as research material is a different status, which our guide on research-use-only products in the Netherlands explains. For athletes under anti-doping rules it is prohibited regardless of how it was obtained.

Is GHRP-6 banned in sport?

Yes, at all times, in and out of competition. The 2026 WADA Prohibited List names it in class S2.2.4, growth hormone-releasing factors, together with GHRP-2, hexarelin and ipamorelin, and the Dutch anti-doping rules apply the same list. See our guide on peptides and the doping list.

Does GHRP-6 make you hungry?

In animals, yes: injected into the brain of rats that had just eaten, it made them start eating again, and it acts on the receptor of ghrelin, the body's hunger hormone. In people, we found no study that measured hunger or food intake after GHRP-6, so the strong hunger described online rests on user reports, not on trials.

Does GHRP-6 build muscle?

There is no evidence that it does in people. It raises growth hormone for a short time after a dose, and during a 34-hour infusion IGF-1 rose by about a quarter, but no controlled trial has measured muscle mass, strength, fat or recovery. The weight-gain finding comes from young rats in the 1984 study.

What is the half-life of GHRP-6?

After an intravenous dose in nine healthy men, blood levels fell in two phases, with half-lives of about 8 minutes and 2.5 hours (Cabrales et al., 2013). We found no human measurements after a subcutaneous injection.

Storage and handling

Store according to product-label instructions and batch handling notes. Lyophilized research peptides are commonly kept dry, protected from light, and handled with clean laboratory technique.

References

Checked against these sources on 28 October 2026.

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