GHRP-6: Growth Hormone-Releasing Peptide-6
First-generation synthetic hexapeptide ghrelin mimetic. Induces strong hunger alongside GH release. Not an approved medicine.
👥 Human studies
- Full name
- GHRP-6 (His-D-Trp-Ala-Trp-D-Phe-Lys-NH2)
- Class
- Ghrelin receptor (GHS-R) agonist — peptide
- Half-life
- ~15–30 minutes
- Route
- Subcutaneous, intranasal
- Developer
- Academic (Bowers, 1980s)
- Regulatory status
- No approval; WADA-banned
What it is
GHRP-6 was the original synthetic ghrelin receptor agonist developed by Cyril Bowers in the 1980s — before endogenous ghrelin was identified. It activates the same receptor and produces a GH pulse, but also strongly stimulates appetite via hypothalamic ghrelin-receptor activation.
How it works
GHS-R1a activation on pituitary somatotrophs drives GH secretion. Parallel activation of hypothalamic neuron populations (particularly arcuate NPY/AgRP) increases hunger — a more prominent effect than with GHRP-2.
Like GHRP-2, GHRP-6 raises prolactin and ACTH/cortisol modestly. Effects synergise with GHRH.
What the research shows
Historical pharmacodynamic studies underpin more modern GH secretagogue programmes.
Bowers CY et al. (1984) — first human GHRP-6 study
Bowers C.Y. et al., Endocrinology 1984;114:1537–1545 (rodent/translational); J Clin Endocrinol Metab 1990;70:975–982 (human). 👥🐀 Human + animal
Acute GHRP-6 IV produced clear dose-dependent GH pulses in healthy adults.
This class of compound validated that non-GHRH, non-somatostatin mechanisms regulate GH secretion — leading decades later to ghrelin discovery.
Limitations: Historical; no long-term data for therapeutic use.
Laferrère B. et al. (2005) — appetite effect
Laferrère B. et al., J Clin Endocrinol Metab 2005;90:611–614. 👥 Human studies
Acute GHRP-6 infusion in healthy adults significantly increased food intake at a subsequent meal.
This orexigenic effect is the most consistent non-GH action and distinguishes GHRP-6 from GHRP-2 and ipamorelin.
Limitations: Acute, not chronic; small cohort.
Safety and limitations
Acute effects well tolerated: flushing, hunger, mild cortisol/prolactin rises. Chronic safety is not established.
Peptides sold in unregulated markets labelled “GHRP-6” vary widely in purity. WADA-banned.