GHRP-6 5mg

What is GHRP-6 ?

GHRP-6, also written GHRP6, is growth hormone releasing hexapeptide: the first synthetic peptide shown to release growth hormone by acting directly on the pituitary. It activates the ghrelin receptor, GHS-R1a. Each GHRP-6 5mg vial holds white lyophilised powder.

Bowers and colleagues (Endocrinology, 1984) described the hexapeptide His-D-Trp-Ala-Trp-D-Phe-Lys-NH₂. It released growth hormone in isolated pituitary tissue and in rats, monkeys, lambs and calves. It did not release LH, FSH, TSH or prolactin, and somatostatin blocked its effect.

The peptide resembled no known hypothalamic hormone, so its receptor stayed unknown for twelve years. Howard and colleagues (Science, 1996) then cloned GHS-R1a and showed it was the target of the synthetic secretagogues. Its natural ligand, ghrelin, was identified three years later.

GHRP-6 Research Applications

GHRP-6 is the founding reference compound in growth hormone secretagogue and ghrelin-receptor research. The Bowers paper set up methods still in use: direct secretagogue activity in isolated pituitary preparations, growth hormone measurement in vivo, and specificity checked against other pituitary hormones. It remains a standard GHS-R1a agonist in receptor-expression systems and binding studies. It is also the usual comparator when newer analogues such as GHRP-2 or ipamorelin are benchmarked. Controlled human data on GHRP-6 are sparse, and it is not an approved therapeutic agent anywhere.

GHRP-6 vs GHRP-2 vs Ipamorelin

All three act at GHS-R1a and come from the same structure-activity lineage. GHRP-6 is the founding hexapeptide at 873.0 g/mol. GHRP-2 keeps the Ala-Trp-D-Phe-Lys-NH₂ end but swaps His-D-Trp for D-Ala-D-2-Nal, giving 818.0 g/mol. Ipamorelin is a later, shorter pentapeptide designed for more selective growth hormone release. The hunger effect is usually linked to GHRP-6, but the controlled human food-intake study in this class used GHRP-2 (Laferrère et al., 2005). Most comparative claims about the three come from early in-vitro and animal work.

Research Overview

GHRP-6, also written GHRP6 or GHRP 6 and spelt out as growth hormone releasing hexapeptide, is the founding compound of the entire growth hormone secretagogue class. It is a synthetic hexapeptide with the sequence His-D-Trp-Ala-Trp-D-Phe-Lys-NH₂, molecular formula C₄₆H₅₆N₁₂O₆, molecular weight 873.0 g/mol and CAS number 87616-84-0, carrying two D-amino-acid substitutions and two tryptophan residues within its six positions. Its characterisation is a landmark paper: Bowers and colleagues (Endocrinology, 1984) reported the in vitro and in vivo activity of a new synthetic hexapeptide that acts on the pituitary to specifically release growth hormone, specifically meaning that in their hands the peptide released GH without behaving as a general secretagogue for the other pituitary hormones measured, and directly meaning that activity was demonstrable in isolated pituitary preparations rather than requiring an intact hypothalamus. That result posed an obvious question, because GHRP-6 resembled no known hypothalamic hormone: what receptor was it acting on? The answer took twelve years. Howard and colleagues (Science, 1996) used peptides of this class to clone an orphan G-protein-coupled receptor from pituitary and hypothalamus, now known as the growth hormone secretagogue receptor GHS-R1a, and the endogenous ligand, ghrelin, was identified three years after that. Essentially every compound now described as a ghrelin mimetic, GHRP-2, ipamorelin, hexarelin and the small-molecule secretagogues, descends from the structure-activity lineage this hexapeptide started. The honest limits are equally clear: GHRP-6 is not a licensed medicine anywhere, controlled human data are sparse, and the comparative claims that circulate about the GHRPs trace overwhelmingly to early in-vitro and animal work rather than head-to-head human trials. This vial contains 5mg of GHRP-6 as a white lyophilised powder, batch UKPL-782 at 98.8% purity by RP-HPLC with the certificate of analysis published on this page, supplied strictly for in-vitro laboratory research use only.

Storage and Reconstitution

Keep sealed vials at -20°C, dry and in the dark. After reconstitution, keep the solution at 2-8°C and use it within 4 weeks, or freeze single-use aliquots at -20°C. Light protection matters more for GHRP-6 than for most peptides of its size. Oxidation of the tryptophans at positions 2 and 4 is the likeliest degradation route, so keep vials and solutions foil-wrapped.

Vials are sold on their own, without bacteriostatic water for mixing or other supplies.

How to reconstitute and handle

Bring the vial to room temperature and swab both stoppers with alcohol. Add bacteriostatic water slowly down the inside wall of the vial and swirl gently until dissolved. Do not shake or vortex. Work away from strong direct light, because both tryptophan residues are light-sensitive. The solution should be clear and colourless. Label the vial with the reconstitution date.

• Protect from light at all stages. GHRP-6 carries two tryptophan residues, at positions 2 and 4, and tryptophan oxidation is the most common degradation route detected by RP-HPLC in stored aromatic peptides.

For the full method, see the peptide reconstitution guide and the reconstitution calculator.

Research References

• On the in vitro and in vivo activity of a new synthetic hexapeptide that acts on the pituitary to specifically release growth hormone (Bowers et al., Endocrinology, 1984)
• A receptor in pituitary and hypothalamus that functions in growth hormone release (Howard et al., Science, 1996)

Published research on GHRP-6 is indexed on PubMed. See our full UK buyer's guide for GHRP-6.