What is GHRP-6?

What sources report

A 1984 report described GHRP-6, His-D-Trp-Ala-Trp-D-Phe-Lys-NH2, as a new synthetic hexapeptide that released growth hormone in a dose-related way from pituitary tissue and in rats, monkeys, lambs and calves, without releasing LH, FSH, TSH or prolactin.⁸ In rats it worked by vein, under the skin or into the abdomen.⁸ Its receptor, a G protein-coupled receptor in the pituitary and hypothalamus, was cloned in 1996, and ghrelin, a 28-amino-acid stomach peptide, was identified as that receptor's natural ligand in 1999.⁹¹⁰ GHRP-6 also binds a second receptor, CD36, which cell and animal studies tie to survival pathways such as PI-3K/AKT1.²⁴

Two human findings shape how it works. Most of its growth hormone effect depends on the body's own GHRH: in 9 healthy men aged 20 to 30, a GHRH blocker cut the peak rise after GHRP-6 from 33.8 to 6.2 µg/L.¹⁷ It also works with GHRH, since low IV doses given together with GHRH released growth hormone synergistically in 18 men.¹² Separately, it increased eating in rats when injected into the brain, an effect the authors suggested is independent of its growth hormone action.³⁰

Human studies

• 1989, 17 healthy men: 30-minute IV infusions raised growth hormone consistently from 0.25 µg/kg upward, left LH, FSH, TSH and ACTH unchanged, and were safe and well tolerated.¹¹
• 1990, 18 healthy men: single IV doses stimulated growth hormone release; prolactin and cortisol about doubled only at the highest dose, and no adverse clinical effects or laboratory abnormalities were seen.¹²
• 1993, 19 obese subjects: one IV dose produced a mean growth hormone peak of 15.7 µg/L, almost twice the response to GHRH, and GHRP-6 plus GHRH produced 42.2 µg/L.¹⁴ The authors concluded that low growth hormone output in obesity is functional and potentially reversible.¹⁴
• 1993, 9 healthy young men: during a 34-hour IV infusion, integrated growth hormone about doubled versus saline and IGF-1 rose from 252 to 312 µg/L, and the pituitary stayed responsive throughout.¹⁵
• 2000, 250 adults: a combined IV test of GHRH plus GHRP-6 separated 125 adults with pituitary disease from 125 healthy adults at a growth hormone cut-off of 15 µg/L, and the hormone peaks caused no side effects.¹⁹

Animal and cell studies

• Heart, pigs (2007): with a 1-hour coronary blockage and 72 hours of reperfusion, GHRP-6 reduced infarct mass by 78% and infarct thickness by 50% versus saline, with signs of antioxidant activity.²¹
• Organ protection (2017 review): protective effects in heart, nerve, gut and liver cells, including less liver damage after interrupted blood flow and less stress damage to the stomach lining in animal models.²⁴²⁵
• Bone, rats (2000): over 12 weeks, GHRP-6, like ipamorelin, increased bone mineral content in adult female rats, but in step with body weight and larger bones; volumetric bone density did not change.⁴²
• Body fat, mice (2001): growth hormone secretagogues, ipamorelin or GHRP-6, increased relative body fat, leptin and food intake by mechanisms the authors judged independent of growth hormone.⁴³

What is not known

A 2026 review places GHRP-6 in an intermediate evidence tier: phase I and small mechanistic human studies of acute hormone responses, no controlled efficacy trials and no long-term safety data.²⁷ The same review says direct evidence for body composition changes in people remains limited, and that heart-protection findings lack confirmation from human clinical trials.²⁷ Most adult studies enrolled only men, in groups of 5 to 18.^111213151722 The compound itself is listed as GHRP-6 for sale in a 5 mg research vial.

Side effects

Human safety data come from small, short studies, mostly single doses or infusions in healthy men, and no long-term safety data exist.^27111215

• Cortisol and ACTH: cortisol about doubled at the highest single IV dose in 18 men, and night-time ACTH and cortisol rose above placebo with repeated doses in a sleep study.¹²¹⁶ ACTH did not change during 30-minute infusions in 17 men.¹¹ FDA names a potential effect on cortisol among its GHRP-6 concerns.⁴
• Prolactin: about 2-fold above baseline at the highest single IV dose, but not at lower doses.¹²
• Appetite: a 2026 review calls appetite stimulation a characteristic effect of GHRP-6.²⁷
• Blood sugar: FDA cites a possible rise in blood glucose from lower insulin sensitivity, and a 2018 review raises the same concern for growth hormone secretagogues as a class.⁴²⁶
• Immune reactions: FDA says compounded GHRP-6 may pose a risk of immunogenicity for certain routes, because of potential aggregation and peptide-related impurities.⁴
• Short-term tolerability: it was described as safe and well tolerated in 17 men, no adverse clinical effects were seen in 18 men, and the 250-person diagnostic study saw no side effects.¹¹¹²¹⁹ A 2017 review reports that IV GHRP-6 proved safe in a dose scale-up trial in healthy volunteers.²⁵
• Class effects: a 2026 review lists prolactin and cortisol rises, appetite changes, blood sugar problems, fluid retention, muscle and joint pain and injection-site reactions among effects reported for growth hormone-axis peptides as a group.²⁸

Warnings

• FDA lists GHRP-6 in category 2 for outsourcing facilities and says it would consider action against a facility that compounds drug products with such a substance.⁴⁵
• Product identity: peptides sold as research compounds come from unregulated supply chains with uncertain composition and dose, and doping and forensic labs have found Gly-GHRP-6, a glycine-extended version, in black-market products and seized powders.²⁸⁴⁰⁴¹
• Athletes: GHRP-6 is prohibited at all times, and an anti-doping lab has added GHRPs to its routine urine screen.⁶²³
• Who was studied: most adult studies enrolled only men, so data in women are sparse.¹¹¹²¹⁵

Dosage information

No human dose of GHRP-6 is established for any use: it has no FDA-approved label, no registered clinical trial and no controlled efficacy trial.³⁶³⁴²⁷ The table lists what published studies gave. These were single or short research exposures, mostly by vein under study supervision, and they are not guidance for people.

Reconstitution and storage

There are no regulator-reviewed instructions for mixing or storing GHRP-6, because it has no FDA-approved label; DailyMed returns none.³⁶ No independent stability data for GHRP-6 vials were found.

Two identity points matter for lab records. PubChem lists GHRP-6 under two CAS numbers, 87616-84-0 and 145177-42-0 (labeled free base), and lists an acetate salt among its synonyms, so a powder's salt form is worth confirming on its certificate.² PubChem's second record, CID 4345065, has the same formula but no defined stereochemistry; CID 9919153 is the record with the D-amino acids defined.¹³ For general lab practice, read How to reconstitute a peptide vial and How to store peptides; the reconstitution calculator converts powder mass and diluent volume into a concentration.

Regulatory status

• United States: not FDA-approved, and DailyMed returned no label when searched on October 24, 2026.³⁶ A 2026 review notes the absence of regulatory approval for physique or performance uses of these peptides.²⁸
• FDA compounding lists: since September 29, 2023, GHRP-6 has sat on FDA's category 2 list for outsourcing facilities (503B), and it was still there on FDA's page current as of April 22, 2026.⁴ FDA cites possible immune reactions, a potential effect on cortisol and higher blood glucose.⁴ On FDA's May 14, 2026 list for pharmacy compounding (503A), GHRP-6 is in category 3: nominated without adequate support.³⁹
• Enforcement context: FDA warning letters dated August 24, 2026 told online peptide sellers that "research use only" labels did not change FDA's finding that their products were unapproved new drugs.³⁷³⁸ The letters reviewed named other peptides, not GHRP-6.³⁷³⁸
• Trials: ClinicalTrials.gov lists no study of GHRP-6, and a broader "GHRP" search returned three studies, none of GHRP-6.³⁴³⁵
• Other countries: no approval of GHRP-6 as a medicine was found. A 2017 review said the GHRP family still awaited a definitive clinical niche, while the related GHRP-2 is approved in Japan as a diagnostic agent for endocrine function.²⁴³¹
• Sport: WADA's 2026 Prohibited List names GHRP-6 in class S2.2.4, banned at all times as a non-Specified Substance, and Finland's anti-doping agency publishes the same classification.⁶⁷

How GHRP-6 compares

• GHRP-2 (pralmorelin): both are synthetic GHRPs in WADA class S2.2.4.⁶ In pigs, GHRP-2 was more potent but less effective at releasing growth hormone, and both raised ACTH and cortisol.¹⁸ See What is GHRP-2?
• Hexarelin: in a similar overnight design (four doses of 50 µg) in 7 volunteers, hexarelin reduced deep sleep and raised prolactin, whereas GHRP-6 lengthened stage 2 sleep without changing slow-wave sleep.²⁹¹⁶
• Macimorelin (Macrilen): an oral drug that acts on the same receptor type.³² FDA approved it in 2017 to diagnose adult growth hormone deficiency with one 0.5 mg/kg dose, and Drugs@FDA now shows Macrilen as discontinued.³²³³
• GHRH analogs such as sermorelin and CJC-1295: WADA lists them as a separate group from GHRPs, and the two classes act together, as the synergy in 18 men showed.⁶¹² See What is Sermorelin?