GHRP-6

GHRP-6 is a synthetic hexapeptide, a chain of six amino acids, with the sequence His-D-Trp-Ala-Trp-D-Phe-Lys-NH2. Two residues are in the D configuration and the C-terminus is amidated, structural features introduced deliberately to slow enzymatic breakdown in laboratory preparations. Its free-base molecular formula is C46H56N12O6 and its average molecular mass is 873.0 g/mol. GHRP-6 shares no sequence homology with growth hormone-releasing hormone and is not a fragment or analogue of it. It is supplied as a lyophilized (freeze-dried) powder, commonly as the acetate salt, and is sold strictly as a research-use-only reference compound.

The published literature classifies GHRP-6 as a growth hormone secretagogue, meaning a compound that acts at the growth hormone secretagogue receptor GHS-R1a rather than at the GHRH receptor. That receptor was cloned in 1996 and its endogenous ligand, ghrelin, was identified in 1999, which recast GHRP-6 as a synthetic ligand for a naturally occurring signalling system. GHRP-6 holds no approved indication in any jurisdiction. It appears most often as a reference agonist in receptor pharmacology work, and in that setting it is routinely confused with the two related synthetic hexapeptides GHRP-2 and hexarelin.

GHRP-6 came out of structure-activity work by Cyril Bowers and Frank Momany, who built a peptide series from a growth hormone-releasing property first noticed in met-enkephalin derivatives. It was characterised in Endocrinology in 1984 (PubMed 6714155).

Later work established receptor identity. Mau and colleagues reported activation of the inositol trisphosphate and diacylglycerol pathway in rat pituitary cells (PubMed 8903947). Howard and colleagues cloned the receptor for the GHRP class (PubMed 8688086), and Kojima and colleagues identified ghrelin as its endogenous ligand (PubMed 10604470).

The evidence base is mature at the receptor level and undeveloped as a therapeutic programme. GHRP-6 never reached approval, much of the record predates current reporting standards, and no efficacy conclusion follows from it.

Published work describes GHRP-6 as an agonist at GHS-R1a, a Gq/11-coupled receptor. The reported cascade runs through phospholipase C, inositol trisphosphate and diacylglycerol generation and calcium mobilisation in somatotroph preparations. That is in vitro signalling, not an outcome in an intact organism.

The distinction researchers most often need is receptor class. GHRP-6 and hexarelin bind the ghrelin receptor. Sermorelin, Mod GRF 1-29, CJC-1295 and tesamorelin are GHRH-receptor analogues acting through a different, cAMP-coupled receptor. Treating the families as interchangeable selects the wrong control compound.

A methodology caveat applies. Most of the record comes from dispersed pituitary cell cultures and rodent models whose receptor density and species pharmacology differ, so reported potencies belong to the assay used.

Sealed lyophilized GHRP-6 is stored frozen, conventionally at -20°C, shielded from light, with repeated freeze-thaw cycles avoided. No duration is stated here: the stability window is documented on the batch Certificate of Analysis.

Two features shape degradation. The two tryptophan residues are photosensitive and oxidation-prone, so light exclusion matters. The powder is hygroscopic, meaning it takes up atmospheric moisture, so a sealed vial is best equilibrated to ambient temperature before opening.

Reconstitution is the term for returning a lyophilized compound to solution; this page defines the term and gives no procedure. GHRP-6 is short, charged and hydrophilic, and sits in the aqueous-soluble class. Preparation parameters belong to the published methodology being reproduced.

Lyophilized peptide is best handled in low humidity with minimal open-container exposure. Lot numbers are recorded against experimental data so identity questions trace back to the right batch and its Certificate of Analysis.

Identity and purity are established by reversed-phase HPLC and mass spectrometry. Verified purity is documented per lot on the Certificate of Analysis rather than as a fixed number. A mass consistent with 873.0 g/mol is the primary identity check.

Counterion and water content affect gravimetric accuracy. Peptides of this class are isolated as acetate or trifluoroacetate salts and retain residual water, so net peptide content on the Certificate of Analysis is the figure to reconcile against vial strength.

GHRP-6 is most usefully read against the wider growth hormone secretagogue literature.

• Hexarelin.
  A closely related hexapeptide at the same ghrelin receptor, studied alongside GHRP-6 in receptor characterisation work.
• Ipamorelin.
  A later ghrelin receptor ligand reported as more selective at GHS-R1a.
• Mod GRF 1-29, Sermorelin and CJC-1295.
  GHRH-receptor analogues that do not bind the ghrelin receptor, the standard class contrast.
• MK-677.
  A non-peptide research compound also acting at the ghrelin receptor.

Bowers CY, Momany FA, et al. (1984). On the in vitro and in vivo activity of a new synthetic hexapeptide that acts on the pituitary to specifically release growth hormone. Endocrinology.
PubMed 6714155

Mau SE, Witt MR, et al. (1995). Growth hormone releasing hexapeptide (GHRP-6) activates the inositol (1,4,5)-trisphosphate/diacylglycerol pathway in rat anterior pituitary cells. J Recept Signal Transduct Res.
PubMed 8903947

Howard AD, Feighner SD, et al. (1996). A receptor in pituitary and hypothalamus that functions in growth hormone release. Science.
PubMed 8688086

Kojima M, Hosoda H, et al. (1999). Ghrelin is a growth-hormone-releasing acylated peptide from stomach. Nature.
PubMed 10604470

GHRP-6 is stocked only as lyophilized powder in sealed single-compound vials, at 5mg and 10mg per vial, across one house brand and two supplier brands. One listing is the acetate salt. Per-vial strengths are specifications, and each lot is batch tested with a published Certificate of Analysis.

• Browse all GHRP-6 research products
• Catalyst Compounds GHRP-6, 5mg vial
• Verified Peptides GHRP-6, 10mg vial
• Real Peptides GHRP-6 Acetate, 10mg vial
• Collections: Research Vials. Documentation: COA and Lab Testing.

These products are sold for Research Use Only and are not intended for human consumption.