GHRP-6

GHRP-6 (growth hormone-releasing peptide-6) is a synthetic six-amino-acid peptide that mimics ghrelin, the stomach hormone that tells the pituitary gland to release growth hormone (GH). It was the first synthetic growth hormone secretagogue (GHS) ever made and still serves as the benchmark compound for the class ¹⁷. A single dose triggers a rapid, dose-dependent GH pulse in humans ²⁴.

GHRP-6 also binds a second receptor, CD36, on immune cells. This second action underlies its anti-inflammatory, anti-fibrotic, and tissue-protective activity in animal studies ¹⁶.

The research literature has examined GHRP-6 for GH-deficiency diagnosis, as an intravenous adjunct to EGF in acute ischemic stroke, and for protection after heart damage, lung injury, kidney injury, and skin wounds ⁶.

GHRP-6 docks to the ghrelin receptor, called GHS-R1a, which normally responds to the stomach hormone ghrelin ¹¹. On pituitary cells this activates a calcium-based signaling route: the cell mobilizes internal calcium and activates protein kinase C, producing a burst of growth hormone into the bloodstream. Unlike GHRH (growth hormone-releasing hormone), GHRP-6 works without the cAMP pathway ²⁹.

The hypothalamus, a control center at the base of the brain, is the main site of action. People with a surgically disconnected pituitary stalk show no GH response to GHRP-6, evidence that the signal must pass through the brain first ³⁵. There the peptide appears to activate GHRH-producing neurons while easing the brake applied by somatostatin ³⁴. It also switches on hunger circuits in the arcuate nucleus, an appetite center, which explains its hunger-stimulating effect ¹¹.

A second mechanism runs through CD36, a receptor on immune cells that helps recognize inflammatory signals. GHRP-6 binding there tones down inflammatory signaling, the proposed basis of its anti-fibrotic and organ-protective results in preclinical work ¹⁷.

Because GHRP-6 and GHRH use different pathways, combining them can produce a GH surge several times larger than either alone. This combined response stays intact in older adults, when plain GHRH responses fade ³⁰.

Growth hormone release

A 1 mcg/kg intravenous dose produces a strong, rapid GH pulse in healthy adults and is a validated test for GH deficiency ²⁴. The response remains intact into late adulthood, unlike the GHRH response ³⁰. This evidence comes from multiple independent human studies ²⁴.

Appetite

Intranasal GHRP-6 increased both meal frequency and meal size in mice and activated appetite (AgRP) neurons in the brain ¹¹. A hunger surge within 15-30 minutes of a dose is the most consistently reported effect at community doses.

Sleep and stress hormones

GHRP-6 raises ACTH and cortisol and increases slow-wave sleep when given in the evening in healthy men ²⁵.

Stroke

A Phase III trial tested intravenous GHRP-6 plus EGF in acute ischemic stroke. The trial missed its primary endpoints overall, but patients with severe stroke (NIHSS, a standard stroke-severity score, of 15 or higher) had less disability at 6 months and lower mortality ¹. An earlier Phase I/II study reported acceptable safety and favorable functional trends ¹³.

Organ and tissue protection

In animals, GHRP-6 reduced post-heart-attack remodeling and scarring ⁶, prevented the heart damage caused by the chemotherapy drug doxorubicin ¹², and cut liver and intestinal ischemia-reperfusion injury by 50-85% ²³. In mouse models it limited acute lung injury and later fibrosis ⁷, and a self-assembling GHRP-6 hydrogel protected kidney tubules after acute kidney injury ⁸. Topical GHRP-6 accelerated wound closure and reduced hypertrophic scarring in animal studies ¹⁶.

Stomach emptying

In diabetic gastroparesis animal models, GHRP-6 sped up gastric emptying through cholinergic nerve pathways ²².

The strongest human dosing data come from acute care and diagnostic studies. Healthy volunteers received 1 mcg/kg by intravenous bolus as a GH stimulation test ²⁴. Stroke trials used 3.5 mg or 5 mg intravenously twice daily for 7 days, combined with EGF ¹. Oral studies in children and older adults used 300 mcg/kg, roughly 300 times the intravenous dose, because digestion breaks down much of the peptide ²⁷.

For research use, the community-standard pattern is 100-300 mcg subcutaneously, one to three times per day on an empty stomach ⁵. Dose spacing follows a documented physiology: injections 60-90 minutes apart produce variable GH responses, while 3 hours or more between doses restores consistent pulses ²⁸. A common research stack pairs GHRP-6 with a GHRH analog such as CJC-1295 or sermorelin, which multiplies the GH output ²⁴. There is no dedicated subcutaneous pharmacokinetic trial for GHRP-6; human pharmacokinetics were characterized after intravenous dosing ²⁰.

Practitioner cycles typically run 8-12 weeks with a 4-week minimum break between cycles; a 5-days-on, 2-days-off variant is common ⁵. The timeline below shows the community schedule in full.

GHRP-6 arrives as a lyophilized (freeze-dried) powder that is dissolved before use. Bacteriostatic water is the standard diluent; sterile water is only suitable when the solution is used the same day. Phosphate-buffered diluents are avoided, because at neutral pH phosphate buffers promote hydrolysis and head-to-tail cyclization of the peptide ¹⁵.

Mix gently: draw the diluent with a fresh syringe and release it slowly down the vial wall, then swirl rather than shake. Store the prepared solution refrigerated (2-8°C) and use within 14-30 days. Protect from light, since tryptophan residues oxidize to 5-hydroxy-tryptophan and kynurenine species ¹⁵.

The peptide is unusually resistant to blood enzymes and digestive enzymes in vitro ⁴⁰, but aqueous solutions degrade by temperature- and pH-dependent kinetics. C-terminal deamidation dominates at pH 3 and pH 8; hydrolysis and cyclization peak at pH 6-7 ¹⁵. Buffer additives and warm, neutral-pH storage also generate degradation products, so refrigeration in bacteriostatic water only is the practical handling rule ¹⁵.

Use the calculator to work out dilution and dose volumes from a given vial size.

Formal drug-interaction studies for GHRP-6 do not exist; this profile combines human stimulation-testing data, animal work, and community experience.

• Glucocorticoids: a single oral dexamethasone dose amplified the GHRP-6 GH response in men, while chronic cortisol excess (Cushing's disease) blunts it ⁴³.
• Somatostatin analogues (octreotide, lanreotide): somatostatin is a functional antagonist of GHRP-6, so these agents blunt its GH effect ³⁴.
• Anticholinergics (atropine): abolished GHRP-6's gastric-emptying effect in diabetic animal models, showing the prokinetic action depends on cholinergic nerves ²².
• Insulin and glucose-lowering agents: GHRP-6 transiently elevates insulin and its metabolic effects depend on insulin/glucose status, an additive hypoglycemia consideration in theory ⁵².
• Recombinant GH (somatropin): suppresses the endogenous axis and counteracts the mechanism GHRP-6 relies on; a multi-decade combined exposure featured in the one osteophyte case ⁴.
• Blood-pressure medications: high intravenous doses caused transient bradycardia in dogs, and ghrelin signaling lowers pressure via sympathetic inhibition in mice ¹⁰.

Peptide pairings: the best documented is EGF plus GHRP-6 in acute stroke, the only GHRP-6 combination with Phase III human safety data ¹. Pairing GHRP-6 with GHRH analogs produces marked synergy ²⁴. The receptor blocker D-Lys3-GHRP-6 is an experimental antagonist used to cancel ghrelin-axis signaling in studies ⁹.

Repeated GHRP-6 doses close together produce a fade in GH responsiveness: injections 60-90 minutes apart give cyclic, attenuated responses, while spacing of 3 hours or more restores consistent release ²⁸. Four days of twice-daily oral dosing preserved the GH response in older adults ³¹, so tolerance is not immediate; it builds with sustained, high-frequency stimulation.

No RCT has tested elective cycling schedules. Community practice uses 8-12 week blocks with a 4-week minimum washout, and 5 days on / 2 days off is a common variant ⁵. The logic: multi-week exposure is needed to accumulate IGF-1-driven effects, while off periods restore sensitivity and limit class-level adverse effects such as fluid retention and glucose drift ⁵.

Signals reported as reasons to pause in practice include fading hunger after dosing, diminished recovery effects, heart-rate changes, and elevated prolactin or cortisol on bloodwork. Long-term human safety data are thin: the longest controlled exposure is 7 days at high intravenous doses ¹, and one case report links roughly 20 years of combined GH-axis use to a symptomatic cervical bone spur (osteophyte) ⁴.

GHRP-6 plus GHRH analogs

The classic stack. GHRP-6 and GHRH operate through separate signaling pathways, so co-administration produces a GH surge roughly 3-4 times either alone, and the synergy is preserved in older adults ²⁴. Community practice pairs 100-200 mcg of GHRP-6 with a GHRH analog such as mod GRF 1-29 or CJC-1295 (no DAC), dosed together 2-3 times daily on an empty stomach ⁵.

GHRP-6 plus EGF

The only combination with Phase III human data. EGF 75 mcg plus GHRP-6 intravenously twice daily for 7 days was safe in stroke trials and improved outcomes in the severe-stroke subgroup ¹.

Combinations the literature argues against

Somatostatin analogues neutralize GHRP-6's GH effect ³⁴. Exogenous GH suppresses the endogenous axis and was part of the one osteophyte case ⁴. The antagonist peptide D-Lys3-GHRP-6 blocks GHRP-6 across models and is used as a research tool, not a companion ⁹.

GHRP-6 has no FDA or EMA approval for any indication. It circulates as an unregulated research compound, and reviews note the absence of quality assurance in gray-market supply chains ⁵. It is not a controlled substance in the US, but it is also not an approved pharmacy bulk ingredient, so legitimate compounding is unavailable ⁵.

The most advanced development program is Cuban: CIGB-845 (EGF plus GHRP-6) completed a Phase III trial in acute ischemic stroke, and CIGB-500 (GHRP-6 alone, for heart attack) completed 28-day dog toxicology with a no-observed-adverse-effect level of 2000 mcg/kg/day ¹. Neither has reached market authorization.

In sport, GHRP-6 is prohibited at all times, in and out of competition, under WADA's S2 class (peptide hormones and growth factors). Anti-doping laboratories run validated LC-MS/MS urine methods that detect the unchanged peptide for about 23 hours after nasal dosing, with metabolites visible roughly 12 hours ¹⁸, and GHRP-6 has been detected in urine samples from athletes ⁶².

In diagnostic testing at 1 mcg/kg intravenously, flushing was the only reported side effect ²⁴. GHRP-6 predictably raises ACTH and cortisol, and evening dosing shifts sleep architecture ²⁵. In the Phase III stroke trial, serious adverse events were numerically higher in the treated group (31.6% vs 19.4%) but none were judged treatment-related ¹.

Animal toxicology is reassuring at short durations: dogs given up to 2000 mcg/kg/day intravenously for 28 days showed only transient hypersalivation, lower activity, and reduced heart rate, all reversible ¹⁰.

Class-level reports from GH-axis peptide users include prolactin and cortisol elevations, fluid retention, joint and muscle aches, dysglycemia, and injection-site reactions ⁵. Appetite increase is the most consistently reported effect at community doses.

Long-term unknowns dominate the safety picture. The longest controlled human exposure is 7 days ¹. A single case report describes a 62-year-old with roughly 20 years of cyclical GH/secretagogue use who developed a cervical osteophyte causing swallowing difficulty; the link is unproven ⁴. Pregnancy and assisted reproduction are areas of concern based on placental GHSR signaling and embryo-development data in mice ⁴⁷.