GHRP-6: what the published research shows

Growth hormone-releasing peptide-6 (GHRP-6), also written growth hormone releasing protein-6 and abbreviated GHRP-6, is a synthetic hexapeptide of the growth hormone secretagogue (GHS) class. It is a ghrelin analog and acts at the growth hormone secretagogue receptor (GHSR), the same receptor engaged by ghrelin. Published work describes it as a six-amino acid synthetic peptide with growth-promoting and immunomodulatory activity in several fish species [11], and reviews of performance-enhancing peptides list it among the GHS agents most commonly encountered in clinical practice and online self-administration protocols, alongside GHRP-2, hexarelin and ipamorelin [5]. The evidence block supplied for this page does not give a sequence, molecular formula or molecular weight, so none is stated here.

The pathway at the centre of the work is the ghrelin/GHSR axis, which couples to growth hormone release and, in the studies below, to cardiac, immune, metabolic and central endpoints.

Research Studies

GHRP-6 and post-infarct ventricular remodelling in rats

In a non-reperfusion myocardial infarct model produced by permanent left descending coronary artery ligation, rats were assigned to sham-operated/normal, infarcted plus saline-treated control, and infarcted plus GHRP-6 groups. The authors had previously determined 0.4 mg/kg as the minimum effective dose for enhancing inotropy by echocardiographic parameters in healthy rats. Treatment began after surgery and continued for 7 days, with echocardiography on day 7. The paper reports that GHRP-6 ameliorated post-infarct ventricular remodelling and systolic dysfunction in this model [1]. This is a rat study; no human cardiac endpoint is reported in the evidence.

GHRP-6 delivered through aquafeeds and endocrine/immune responses in Sparus aurata

Gilthead seabream (Sparus aurata) received GHRP-6 included in the diet at 500 µg/kg of feed. After 97 days, fish were injected intraperitoneally with 100 µL of saline solution or IFA per 100 g fish, and endocrine and immune responses were sampled. The study assessed whether the ghrelin analog modulated those responses following Incomplete Freund's adjuvant treatment [2]. This is a fish aquaculture model.

GHRP-6 and locomotor activity during acute nicotine withdrawal in rats

Male and female Wistar rats were injected intraperitoneally with 2 mg/kg nicotine or saline twice daily for 7 days, then subjected to acute nicotine withdrawal, and horizontal and vertical activity were measured. Ghrelin and GHRP-6 act through the same receptor, and both were tested for effects on withdrawal-associated changes in locomotor activity. The paper reports that changes in locomotor activity observed during acute nicotine withdrawal can be attenuated by ghrelin and GHRP-6 in rats [3].

GHRP-6 and human oocyte maturation in in vitro maturation culture media

This experimental study collected 240 human germinal vesicle (GV) oocytes and cultured them in varying concentrations of GHRP-6, described as a ghrelin hormone agonist, with maturation rates assessed during culture. The stated aim was to determine the most effective concentration of GHRP-6 in the culture medium for improving human oocyte maturation and meiotic progression in in vitro maturation (IVM) [7]. This is an in vitro study on human oocytes; it is not a clinical trial and reports no pregnancy or live-birth endpoint.

GHRP-6 and the ghrelin system in broiler chickens

Four experiments were conducted in broiler chickens, each with four experimental groups, using intracerebroventricular (ICV) injection. In one experiment, birds received saline or LEAP-2 at 0.75, 1.5 or 3 nmol; in another, birds received saline or (D-Lys-3)-GHRP-6 at 0.5 nmol, a GHSR antagonist used to probe ghrelin and cannabinoid interactions on food intake [6]. This is an avian model and the GHRP-6-related agent here is the antagonist (D-Lys-3)-GHRP-6, not GHRP-6 itself.

GHRP-6 and the ghrelin–dopamine cascade in a rat model of depression

A novel butyrylcholinesterase inhibitor was evaluated in the Flinders Sensitive Line (FSL) rat model of major depressive disorder, with behavioural assessment by forced swim test, sucrose preference test and novel object recognition test, and with brain dopamine measures. The paper frames the effects as involving the ghrelin–dopamine cascade [8]. GHRP-6 is not the administered agent in this study; it is relevant to the page because it defines the ghrelin-side pharmacology of that cascade.

GHRP-6 in acute lung injury and progression to interstitial fibrosis

Acute lung injury and acute respiratory distress syndrome involve acute onset, alveolar damage and progressive hypoxemia, with a proliferative phase that can drive pulmonary fibrosis; lipopolysaccharide (LPS) and zymosan (ZYM) induced lung injury are commonly used biomodels that recapitulate much of this. The paper reports that GHRP-6 ameliorates acute lung injury and its subsequent evolvement to interstitial fibrosis [9]. This is a preclinical injury model.

GHRP-6 hydrogel and acute kidney injury

Renal tubular epithelial cells are highly susceptible to injury during acute kidney injury and have notable regenerative effects on renal recovery afterwards, and AKI-driven metabolic reprogramming of these cells helps determine whether kidneys recover functionally or develop fibrosis. The paper reports a GHRP-6 hydrogel approach for acute kidney injury therapy via metabolic regulation [10]. This is preclinical.

GHRP-6 and nervous necrosis virus infection

GHRP-6 is described as a six-amino acid synthetic peptide acting as a ghrelin analog with growth-promoting and immunomodulatory activities in several fish species. This study evaluates its effects against infection with nervous necrosis virus (NNV), an important pathogen in fish [11]. This is a fish pathogen model.

Comparison of models and reported endpoints

GHRP-6 in the wider GH-IGF-1 peptide literature

A review of performance-enhancing peptides marketed as research compounds places GHRP-6 within the growth hormone secretagogue group that modulates the GH-IGF-1 axis, together with GHRH analogues such as sermorelin, tesamorelin and CJC-1295 with and without DAC, other GHS such as GHRP-2, hexarelin and ipamorelin, the GH fragment AOD9604 (hGH 176-191), and IGF-1 analogues. The review describes a gap between clinical evidence and patient self-administration for this class [5].

Related ghrelin-pathway observations

Two further papers in the evidence concern ghrelin rather than GHRP-6 directly. A case report describes a 62-year-old male ex-military recreational bodybuilder, a long-term growth hormone user, who presented with cervicalgia and left shoulder pain and was found to have multilevel degenerative cervical changes including a prominent anterior osteophyte at C3-C4 compressing the esophagus, with intermittent dysphagia for larger food boluses [4]. Separately, work on controlled ovarian hyperstimulation reports that COH increases circulating ghrelin and examines its role in COH-induced alterations [12]. Neither establishes an effect of GHRP-6.

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Sources

• [1] Growth Hormone-Releasing Peptide-6 (GHRP-6) Ameliorates Post-Infarct Ventricular Remodeling and Systolic Dysfunction in a Model of Permanent Coronary Ligation — https://europepmc.org/article/PMC/PMC13029777
• [2] The Ghrelin Analog GHRP-6, Delivered Through Aquafeeds, Modulates the Endocrine and Immune Responses of Sparus aurata Following IFA Treatment — https://europepmc.org/article/PMC/PMC12383794
• [3] Changes in Locomotor Activity Observed During Acute Nicotine Withdrawal Can Be Attenuated by Ghrelin and GHRP-6 in Rats — https://europepmc.org/article/PMC/PMC11761252
• [4] Anterior cervical osteophyte-related dysphagia in a long-term growth hormone user: a case report — https://europepmc.org/article/PMC/PMC13375183
• [5] The emerging landscape of performance-enhancing peptides modulating GH-IGF1 axis — https://europepmc.org/article/PMC/PMC13322892
• [6] Effect of intracerebroventricular (ICV) injection of antimicrobial peptide expressed in the body-2 (LEAP-2) and its interaction with cannabinoid and ghrelin systems on food intake in broiler chickens — https://europepmc.org/article/PMC/PMC12950399
• [7] Assessing The Effectiveness of Growth Hormone Releasing Protein-6 in Improving Human Oocyte Maturation and Meiotic Progression in In Vitro Maturation Culture Media — https://europepmc.org/article/PMC/PMC12530215
• [8] A novel butyrylcholinesterase inhibitor induces antidepressant, pro-cognitive, and anti-anhedonic effects in Flinders Sensitive Line rats — https://pubmed.ncbi.nlm.nih.gov/40318448/
• [9] Growth hormone releasing peptide-6 (GHRP-6) ameliorates acute lung injury and its subsequent evolvement to interstitial fibrosis — https://pubmed.ncbi.nlm.nih.gov/41534456/
• [10] Growth hormone-releasing peptide 6 (GHRP-6) hydrogel for acute kidney injury therapy via metabolic regulation — https://europepmc.org/article/PMC/PMC12777158
• [11] Anti-nervous necrosis virus activity of the growth hormone releasing peptide-6, GHRP-6 — no URL provided in evidence block
• [12] Ghrelin impairs embryo development after ovarian hyperstimulation — https://pubmed.ncbi.nlm.nih.gov/42461148/