RESEARCH MONOGRAPH · KDC-MN-077

GHRP-6

May 9, 2026 Kodiac biolabs Research Revised May 30, 2026 2 min read

Our opinion on this compound

71/100

The classic ghrelin mimetic, useful but with cortisol and prolactin elevation that often gets ignored

GHRP-6 is the elder statesman of synthetic growth hormone secretagogues. Bowers' group at Tulane synthesized it in the late 80s as an extension of the original GHRP work, and it's been the reference compound in countless GH-axis studies since. Structurally a hexapeptide (His-D-Trp-Ala-Trp-D-Phe-Lys-NH2), it agonizes GHSR1a (the ghrelin receptor) at low nanomolar potency.

What we like: there's a lot of good basic research on this molecule. The hypothalamic effects on NPY/AgRP feeding circuits, the GH pulse pharmacology, the cardioprotective effects in ischemia-reperfusion models from the Belgian Isgaard group, and the use as a positive control in GH secretagogue research are all well-established. As a tool compound for studying ghrelin receptor pharmacology, GHRP-6 has decades of literature behind it.

What we dont like is the cortisol and prolactin story. GHRP-6 reliably elevates both at GH-release doses, which is partly an unavoidable consequence of GHSR1a activation in the pituitary and partly off-target HPA-axis effects. The cortisol bump is meaningful enough that for studies trying to isolate GH from stress-axis effects, GHRP-2 or ipamorelin is a cleaner choice. The appetite stimulation is also substantial (this is the prototype peptide for ghrelin-receptor-mediated feeding), which can be useful or annoying depending on whats being studied.

The pharmacokinetics are predictable with half-life around 15 minutes and rapid GH peak. Combination work with GHRH analogs (sermorelin, CJC-1295) is straightforward. Tolerance to repeated dosing is real but manageable.

Sourcing is mature. Reputable peptide vendors all produce HPLC-pure GHRP-6 reliably; the synthesis is standard Fmoc-SPPS and the molecule is forgiving. Watch for tryptophan oxidation in poorly-stored lots and verify chromatograms.

For ghrelin pharmacology and as a positive control in GH-axis work, GHRP-6 is foundational. For applications where you need cleaner GH selectivity, prefer ipamorelin or GHRP-2. The classic status is earned but the cleaner descendants matter.

Evidence: 65
Mechanism: 82
Reliability: 72
Safety: 70
Sourcing: 80
Value: 75
Signal: 68
Staying power: 58

Plain-language summary Intrigue 58 / 100

GHRP-6 is the original growth hormone releasing peptide and a strong appetite stimulant (because it activates the ghrelin receptor that controls hunger). It produces robust growth hormone release but with the most pronounced cortisol and prolactin elevation among the GHRPs. Not stocked by Kodiac. This monograph is provided for research and educational reference.

Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.

Growth hormone releasing peptide / ghrelin receptor agonist

A first-generation hexapeptide ghrelin receptor agonist with prominent appetite stimulation, often used as a research-grade alternative to ipamorelin.

Abstract

GHRP-6 (His-D-Trp-Ala-Trp-D-Phe-Lys-NH2; CAS 87616-84-0; molecular formula C46H56N12O6; molecular weight 873.02) is a first-generation hexapeptide ghrelin receptor agonist. The compound stimulates GH release with kinetics similar to GHRP-2 but produces more pronounced cortisol and prolactin elevation, which has limited its clinical development. GHRP-6 also produces marked appetite stimulation through ghrelin pathway activation, an effect that distinguishes it from later GHRPs and that may be either useful (cachexia, sarcopenia adjunct) or unwanted (weight management contexts) depending on the application. Pharmacokinetics: plasma half-life 15 to 60 minutes; parenteral administration only. Reported research dose ranges in the literature span approximately 100 to 300 micrograms subcutaneously.

Mechanism of action

Ghrelin receptor agonist; same class as GHRP-2 with more cortisol/prolactin elevation and stronger appetite stimulation.

Reported research dose ranges

Reported research dose ranges in the literature span approximately 100 to 300 micrograms subcutaneously.

References

Bowers CY, et al. Growth hormone releasing peptides. Endocrinology 1990s.

Read the full monograph

The full reference document covers compound identification, discovery and developmental history, mechanism of action, pharmacokinetics, reported research dose ranges, sourcing and quality verification, reconstitution and handling, stack interaction considerations, and a curated reference list. Available as a research-use-only PDF download.

KDC-MN-077

The full reference document is provided strictly for research use only. It reports research dose ranges from the published literature, not instructions for use in humans or animals.

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FOR RESEARCH USE ONLY. Not for medical, diagnostic, or therapeutic purposes. Not for human consumption. All information is provided for research and educational purposes only.

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GHRP-6

Abstract

Mechanism of action

Reported research dose ranges

References

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Abstract

Mechanism of action

Reported research dose ranges

References

Read the full monograph

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