GHRP-4
Growth hormone-releasing peptide-4, GHRP4, D-Trp-Ala-Trp-D-Phe-NH2
GHRP-4 is a synthetic tetrapeptide corresponding to a truncated member of the growth hormone-releasing peptide family, retaining the aromatic core that gives the class its activity at the ghrelin receptor. It is essentially a structure-activity relationship stepping stone rather than a developed compound. There is no published human data on it at all, and the only direct experimental data on this exact sequence is analytical serum-stability work.
Mechanism
GHRP-4 belongs to the family of synthetic growth hormone secretagogues that act at the growth hormone secretagogue receptor type 1a (GHS-R1a), the receptor later found to be the endogenous target of ghrelin. Agonism at this Gq/11-coupled receptor on pituitary somatotrophs activates phospholipase C, raises intracellular calcium and triggers release of stored growth hormone; parallel activity in the hypothalamus counteracts somatostatinergic restraint. This mechanism runs in parallel to, and synergises with, the separate GHRH receptor pathway.
What distinguishes GHRP-4 within the family is that it is a truncation, not an elaboration. Structure-activity work in this series identified the core Ala-Trp-(D-Phe)-Lys motif as the essential pharmacophore, with the aromatic side chains of tryptophan and D-phenylalanine and the basic lysine contributing most of the receptor contact; Ferro and colleagues later mapped how modifications at positions 1, 2, 3 and 7 alter GHS-R1a binding. GHRP-4 keeps a Trp-Ala-Trp-Phe arrangement and drops both the C-terminal lysine and any N-terminal extension found in GHRP-1, GHRP-2 and GHRP-6. Losing the lysine would be expected to reduce receptor affinity relative to the hexapeptide and heptapeptide members, and the longer analogues, not this one, were carried forward. Two caveats belong here. First, there is no published receptor binding constant, no potency comparison against ghrelin and no in vivo dose-response curve for this specific tetrapeptide in the peer-reviewed literature. Second, the assumption that truncation also costs metabolic stability is not supported: serum and enzymatic stability profiling published in 2023 found GHRP-4 sufficiently stable to serve as an internal standard in bioanalytical work.
What the research shows
The honest position on GHRP-4 is that there is almost nothing to report. It has no dedicated pharmacology publication. The numbered GHRP designations arose from the Momany and Bowers programme, in which enkephalin-derived peptides were screened on rat pituitary cells; the 1981 and 1984 papers report the specific pentapeptides and hexapeptides that defined the series, and it was GHRP-6, GHRP-2 and hexarelin, not the shorter truncations, that human work followed. Where GHRP-4 appears in the modern indexed literature it is almost exclusively as an analytical target: it is one of the eight GHRPs covered by the 2011 Cologne urine screening method, and it is one of six peptides synthesised and profiled in the 2023 in-house standards study, which concluded that GHRP-4, GHRP-6 and sermorelin(22-29) were stable enough in serum and enzyme incubations to serve as internal standards.
There are no in vivo efficacy data specific to GHRP-4 in any species. There are no human exposures, no pharmacokinetic data, no toxicology and no controlled outcome studies of any kind. Claims made for it in commercial listings - that it raises growth hormone potently, improves sleep, aids recovery or promotes fat loss - are extrapolations from better-studied members of the family and are not supported by any published work on this molecule. Where the family has been tested properly in humans, the numbered GHRPs release growth hormone acutely, but that acute release has never been shown to translate into durable clinical benefit; treating GHRP-4 as though it inherits proven benefits from its relatives inverts the actual evidence, because even the well-studied relatives have not demonstrated those benefits.
Evidence assessment
Preclinical only
There is no human data whatever. The only work on this exact sequence is in vitro serum and enzyme stability profiling plus inclusion as an analytical target in anti-doping screens; the pharmacology data belong to the wider Momany and Bowers series rather than to this tetrapeptide. Preclinical is the correct tier and is arguably generous.
Tiers are applied consistently across the library and re-checked when new trials read out. Read the grading method.
Key studies
In-house standards derived from doping peptides: Enzymatic and serum stability and degradation profile of GHRP and GHRH-related peptides Preclinical only
Matrix effects and sample pretreatment significantly affected peptide recovery from biological matrices. GHRP-4, GHRP-6 and sermorelin(22-29) were sufficiently stable enzymatically and in serum to be proposed as in-house internal standards for bioanalytical quantification.
Determination of growth hormone releasing peptides (GHRP) and their major metabolites in human urine for doping controls by means of liquid chromatography mass spectrometry Preclinical only
Validated an LC-MS method extracting eight known GHRPs from urine, plus the characterised metabolite of GHRP-2, with detection limits of 0.2-1 ng/ml and recoveries of 47-95 per cent. After 10 mg oral GHRP-2, the metabolite remained detectable for over 20 hours although the intact drug was not recovered.
Design, synthesis, and biological activity of peptides which release growth hormone in vitro Preclinical only
Iterative conformational design from weakly active enkephalin-derived leads produced Tyr-D-Trp-Ala-Trp-D-Phe-NH2, active at 10-30 ng/ml in vitro and about 1000-fold more potent than the starting compounds; active and inactive analogues were compared to propose a receptor-binding model.
Conformational energy studies and in vitro and in vivo activity data on growth hormone-releasing peptides Preclinical only
Reported the pentapeptide His-D-Trp-Ala-Trp-D-Phe-NH2 and the hexapeptide His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 as active in vitro at low concentrations and effective in vivo at modest doses, and related conformation to potency across the series.
Structure-activity relationship for peptidic growth hormone secretagogues Preclinical only
Several GHRPs and truncated analogues sharing the core Ala-Trp-(D-Phe)-Lys were assayed at GHS-R1a, and modifications at positions 1, 2, 3 and 7 were shown to influence binding, providing the structural rationale for why truncated members were not developed further.
Safety
No safety data exist for GHRP-4 in humans or animals. Nothing about the absence of reported harm should be read as reassurance; nobody has looked. The theoretical risk profile is that of the growth hormone secretagogue class: acute cortisol and prolactin release, appetite stimulation, and with sustained exposure the consequences of raised growth hormone and IGF-1 including fluid retention, arthralgia, carpal tunnel symptoms and impaired glucose tolerance. Growth hormone axis stimulation is inappropriate in anyone with active malignancy, proliferative diabetic retinopathy or untreated pituitary disease. In practice the more immediate hazard is the supply chain: material sold under this name is manufactured without pharmaceutical oversight, and identity, purity, sterility and endotoxin content are unverified. Confusion between the several numbered GHRPs in commercial supply is common.
Regulatory status
| Jurisdiction | Status |
|---|---|
| United Kingdom | No UK marketing authorisation. Supply for human use would constitute supply of an unlicensed medicinal product under the Human Medicines Regulations 2012. |
| United States | Not approved by the FDA for any indication. It is an unapproved new drug and not a lawful dietary supplement ingredient; distributed only as a research chemical labelled not for human consumption. |
| WADA (sport) | Prohibited at all times. Growth hormone-releasing peptides fall under section S2.2.3 of the WADA Prohibited List, where GHRP-4 is named among the examples. The draft cited section S2.1, which is the erythropoietin section and is incorrect. |
Questions
Because it was a stepping stone, not a candidate. In the original structure-activity programme, short truncated peptides helped define which residues mattered, but the longer analogues bound the receptor better. Development effort went to GHRP-6, GHRP-2 and hexarelin. GHRP-4 was left behind and never picked up again except as an analytical reference peptide.
Nobody has published a study that would answer this. The family it belongs to does raise growth hormone acutely, but no human has been given GHRP-4 in any published trial, so its potency, duration and even whether it works at practical exposures are unknown.
Structure-activity work predicts lower receptor affinity, because it lacks the C-terminal lysine and the N-terminal residues that contribute to binding in the longer analogues. There is no published head-to-head potency comparison for this exact sequence, so the size of any difference is not established. Its metabolic stability, by contrast, appears reasonable: a 2023 study found it stable enough in serum to use as an analytical internal standard.
Yes. Anti-doping laboratories have validated liquid chromatography-mass spectrometry methods covering eight GHRPs in urine, and GHRP-4 is named on the WADA Prohibited List under section S2.2.3.