GHRP-6

Also known as: Growth Hormone Releasing Peptide 6, GHRP6, SKF-110679

Evidence: Clinical

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Overview

First synthetic GH-releasing hexapeptide (Bowers 1984); raised GH dose-dependently and synergized with GHRH in normal men (n=18). Appetite and gut-motility effects are documented in rodents.

GHRP-6 (His-D-Trp-Ala-Trp-D-Phe-Lys-NH2) is the first synthetic growth hormone-releasing peptide, described by Bowers in 1984 before its receptor (GHS-R1a) or its natural ligand ghrelin were known. In normal men, IV doses of 0.1-1 mcg/kg raised peak GH from 1 to 69 mcg/L and acted synergistically with GHRH; prolactin and cortisol roughly doubled at the 1 mcg/kg dose (Bowers 1990, n=18). GHRH plus GHRP-6 became a diagnostic stimulus whose GH response is preserved into old age (Micic 1998). Cuban groups report tissue-protective effects: a 400 mcg/kg dose cut infarct mass 78% in pigs (Berlanga 2007), and GHRP-6 combined with EGF was safe in a phase 1/2 randomized open-label stroke trial (Hernandez-Bernal 2024, n=36). Human PK exists for IV dosing (Cabrales 2013). It is not approved as a drug in any jurisdiction.

Benefits

GH release and GHRH synergy (human, n=18), reduced myocardial infarct size (pig), safety and functional signal in acute stroke with EGF (human phase 1/2, n=36, open label), bone mineral content (rat), food intake and gut transit (rat)

Dosing reference

Research dose: 0.1-1 mcg/kg IV in human GH studies (about 70 mcg at 1 mcg/kg); 90 mcg IV in the GHRH+GHRP-6 test; research-community range 100-300 mcg SC 1-3x daily
Range: 100 to 300 mcg, 2-3x daily
Reconstitution: 2 mL bacteriostatic water
Common vial sizes: 5 mg, 10 mg

Subcutaneous or IV in research; human GH studies used IV bolus. GH peak occurs within about 30 min. Prolactin and cortisol rose about 2-fold at 1 mcg/kg IV in men (Bowers 1990). Elimination half-life after IV bolus is about 2.5 h (Cabrales 2013).

Mechanism

GHRP-6 is an agonist at the growth hormone secretagogue receptor GHS-R1a, the receptor later found to bind ghrelin (Kojima 1999). It releases GH from pituitary somatotrophs by a pathway separate from GHRH, and the two stimuli synergize in men (Bowers 1990). At 1 mcg/kg IV it also roughly doubled prolactin and cortisol in men (Bowers 1990). In the heart, GHRPs bind CD36 as well as GHS-R1a; CD36 mediates the coronary effects of hexarelin in mice and is a proposed mechanism for the GHRP-6 cardioprotection seen in pigs (Berlanga 2007).

Evidence

Clinical: at least one published human trial or an approved drug

Raised peak GH from 1 to 69 mcg/L at 1 mcg/kg IV and synergized with GHRH in normal men, n=18 (Bowers et al., 1990)
GHRH + GHRP-6 (90 mcg each, IV) produced a preserved GH response in subjects aged 19-96 (Micic et al., 1998)
IV bolus 100-400 mcg/kg: distribution half-life 7.6 min, elimination half-life 2.5 h in nine healthy men (Cabrales et al., 2013)
400 mcg/kg reduced infarct mass 78% after coronary occlusion in pigs (Berlanga et al., 2007)
EGF + GHRP-6 (3.5-5 mg IV twice daily, 7 days) was safe in a phase 1/2 randomized open-label stroke trial, n=36 (Hernandez-Bernal et al., 2024)
Human-trial status: decades of acute human GH studies and one phase 1/2 combination trial; not approved anywhere

References

Side effects

In men, 1 mcg/kg IV produced no adverse clinical effects; prolactin and cortisol rose about 2-fold at that dose (Bowers 1990). Adverse events in the stroke trial did not exceed control (Hernandez-Bernal 2024). Appetite increase, water retention, tingling in the hands, lethargy and reduced insulin sensitivity are commonly reported (anecdotal) with repeated SC use. Regulatory: GHRP-6 is on FDA's 503B category 2 (significant safety risks) table, added 2023-09-29, page content as of 2026-04-22: https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks

Storage

Storage: Refrigerated (2-8°C)
Lyophilized: 24+ months at room temperature
Reconstituted: 28-30 days refrigerated

Pharmacology

Half-life: ~2.5 h elimination, 7.6 min distribution (human, IV bolus; Cabrales 2013)
Molecular weight: 873.01 Da
Sequence: H[D-W]AW[D-F]K[NH2]