Scientific Reference
GHRP-6
Evidence profile: Human Phase 1 evidence
GHRP-6 is a synthetic hexapeptide, His-D-Trp-Ala-Trp-D-Phe-Lys-NH2, and one of the earliest growth hormone-releasing peptides to be described. It came out of structure-activity work on small synthetic peptides, carried out before anyone knew which receptor they acted on. That receptor, GHS-R1a, was later shown to respond to ghrelin, a hormone made mainly in the stomach, so GHRP-6 is now classed as a ghrelin receptor agonist. It has been used in pituitary cell and receptor assays, in a large body of animal work, and in human endocrine studies of hormone secretion. Because the same receptor takes part in the control of feeding, it has also served as a tool in appetite research.
Mechanism of Action
GHRP-6 is reported to bind and activate GHS-R1a, a G protein-coupled receptor that signals mainly through Gq, phospholipase C and intracellular calcium. On pituitary somatotrophs this signalling triggers growth hormone release. The receptor is also expressed in the hypothalamus, including on neuropeptide Y and agouti-related peptide neurons of the arcuate nucleus, which rodent studies have linked to the control of food intake; that distribution is the basis for the peptide's use in feeding research. Small increases in ACTH, cortisol and prolactin have been reported with it in addition to growth hormone. Interactions with somatostatin signalling have been proposed but are less clearly defined.
Molecular Information
- Type: Growth hormone secretagogue (GHRP)
- Length: 6 amino acids
- Molecular weight: 873.0 g/mol
- Molecular formula: C46H56N12O6
Published Research
Pharmacokinetic study of Growth Hormone-Releasing Peptide 6 (GHRP-6) in nine male healthy volunteers
Cabrales A et al. · European journal of pharmaceutical sciences : official journal of the European Federation for Pharmaceutical Sciences · 2013 · Clinical
PMID 23099431 — View on PubMedEffects of ghrelin, GH-releasing peptide-6 (GHRP-6) and GHRH on GH, ACTH and cortisol release in hyperthyroidism before and after treatment
Molica P et al. · Pituitary · 2010 · Clinical
PMID 20602173 — View on PubMedGrowth hormone responses to GH-releasing peptide (GHRP-6) in hypothyroidism
Pimentel-Filho FR et al. · Clinical endocrinology · 1997 · Clinical
PMID 9156038 — View on PubMedDifferent effects of growth hormone releasing peptide (GHRP-6) and GH-releasing hormone on GH release in endogenous and exogenous hypercortisolism
Borges MH et al. · Clinical endocrinology · 1997 · Clinical
PMID 9274702 — View on PubMedGrowth hormone secretion after the administration of GHRP-6 or GHRH combined with GHRP-6 does not decline in late adulthood
Micic D et al. · Clinical endocrinology · 1995 · Clinical
PMID 7734029 — View on PubMedGrowth hormone-releasing peptide-6 stimulates sleep, growth hormone, ACTH and cortisol release in normal man
Frieboes RM et al. · Neuroendocrinology · 1995 · Clinical
PMID 7617137 — View on PubMed