GHRP-6
updated
GHRP-6 is one of the original synthetic ghrelin-receptor agonists, a six-amino-acid peptide triggering growth hormone release; no FDA-approved version was identified. It is used for muscle, fat loss, injury recovery, sleep and, by some, a strong appetite boost while bulking. In 18 normal men, the highest single dose raised peak growth hormone to 68.7 mcg/L against 1.2 on placebo, but prolactin and cortisol roughly doubled, and no controlled trial tested muscle, fat loss, recovery or lasting sleep benefit. Graded D for real human pharmacology without an outcome record for its marketed uses.
synthetic hexapeptide ghrelin-receptor agonist
- Synthetic hexapeptide
- Activates the ghrelin receptor
- Human endocrine and sleep experiments exist
- No FDA-approved GHRP-6 drug identified
What is GHRP-6?
GHRP-6 is a synthetic six-amino-acid ghrelin-receptor agonist and growth-hormone secretagogue. It is distinct from GHRP-2, ipamorelin, hexarelin, and GHRH analogues.
source: Sleep study · stage 2 and cortisol increased, Frieboes RM et al. Neuroendocrinology, 1995.
source: Route study · six volunteers, Huhn WC et al. Journal of Clinical Endocrinology and Metabolism, 1991.
What has GHRP-6 shown in people?
Small acute studies show GH release and changes in ACTH, cortisol, prolactin, appetite-related physiology, and sleep architecture. No controlled muscle, fat-loss, recovery, or durable insomnia outcome trial was identified.
Did GHRP-6 improve sleep?
It increased stage 2 sleep in one overnight experiment but did not increase slow-wave sleep. The study did not show better daytime function, insomnia remission, or long-term sleep quality.
source: Sleep study · stage 2 and cortisol increased
source: Human physiology · repeated IV exposure, Frieboes RM et al. 1999.
source: Route study · six volunteers
Is GHRP-6 selective for growth hormone?
Human experiments changed ACTH, cortisol, and sometimes prolactin as well as growth hormone. GHRP-6 therefore did not produce isolated GH release in those studies.
source: Sleep study · stage 2 and cortisol increased
source: Route study · six volunteers
source: Human study · metabolic response, Broglio F et al. Journal of Clinical Endocrinology and Metabolism, 2001.
What are the main safety limits?
The human experiments were small and short. Repeated outpatient use may affect appetite, cortisol, glucose, and insulin sensitivity, while immune reactions, pregnancy, combinations, and product quality remain inadequately characterized.
An acute hormone study cannot supply a chronic adverse-event rate. Effects may also differ with diabetes, corticosteroids, growth-hormone-axis disease, or combined secretagogues.
source: Human study · metabolic response
source: FDA safety page · cortisol and glucose concerns, U.S. Food and Drug Administration.
Is GHRP-6 FDA approved?
No FDA-approved GHRP-6 drug was identified. FDA lists compounding safety concerns, and WADA prohibits growth-hormone secretagogues for covered athletes.
source: FDA safety page · cortisol and glucose concerns
source: WADA 2026 · GH secretagogues, World Anti-Doping Agency, effective 1 January 2026.
Studies and sources
Sleep study · stage 2 and cortisol increased
Controlled human physiology study
Frieboes RM et al. Neuroendocrinology, 1995.
Normal men received four 50-microgram intravenous boluses or placebo overnight. GH, ACTH, cortisol, and stage 2 sleep increased, while slow-wave sleep did not. More stage 2 sleep is not proof of better sleep quality or insomnia treatment.
- Participants / model
- Healthy male volunteers
- Treatment
- Four intravenous 50-microgram GHRP-6 boluses or placebo
- Follow-up
- One overnight study
- Study design
- Placebo-controlled sleep-EEG and hormone study
Human physiology · repeated IV exposure
Controlled human physiology study
Frieboes RM et al. 1999.
Repeated intravenous GHRP-6 altered GH, ACTH, cortisol, and selected sleep measures in healthy volunteers. The experiment measured acute physiology, not chronic clinical sleep, recovery, or body composition.
- Participants / model
- Healthy adult volunteers
- Treatment
- Repeated intravenous GHRP-6
- Study design
- Controlled sleep and endocrine experiment
Route study · six volunteers
Human pharmacology study
Huhn WC et al. Journal of Clinical Endocrinology and Metabolism, 1991.
Six healthy men received GHRP-6 intravenously or intranasally. GH increased, and small prolactin and cortisol responses were reported. The tiny acute study does not establish long-term nasal bioavailability or safety.
- Participants / model
- Six healthy men
- Treatment
- Intravenous or intranasal GHRP-6
- Study design
- Acute route and endocrine-response study
Human study · metabolic response
Human physiology study
Broglio F et al. Journal of Clinical Endocrinology and Metabolism, 2001.
The study examined glucose and insulin responses around acute GHRP-6 exposure. It supports endocrine-metabolic activity but does not characterize long-term diabetes risk or weight-loss benefit.
- Participants / model
- Healthy adult volunteers
- Treatment
- Acute GHRP-6 exposure
- Study design
- Human endocrine-metabolic study
FDA safety page · cortisol and glucose concerns
FDA safety communication
U.S. Food and Drug Administration.
FDA cites limited safety information, possible cortisol effects, decreased insulin sensitivity and increased blood glucose, plus immunogenicity and peptide-impurity concerns.
- Study design
- Agency safety summary
WADA 2026 · GH secretagogues
Sports rule
World Anti-Doping Agency, effective 1 January 2026.
Growth-hormone secretagogues are prohibited under S2 for athletes covered by the Code.
- Study design
- Binding sport rule for covered athletes
Why is GHRP-6 in D tier?
D tier comes from direct human pharmacology without a persuasive therapeutic outcome record for current marketed uses.
how tiers are graded: methodology · every cited source · about reptides.
Research reference, not medical advice. Entries distinguish product labels, study doses and reported protocols. Check the linked source for the product, route and population.