GHRP-5
Growth hormone-releasing peptide-5, GHRP5, Momany peptide, Tyr-D-Trp-Ala-Trp-D-Phe-NH2
GHRP-5, sometimes called the Momany peptide, is a synthetic pentapeptide from the original growth hormone-releasing peptide series and was the most potent compound reported in the founding 1981 structure-activity paper. Its most cited later experimental work is not about growth hormone at all but about prolactin release from rat pituitary lactotrophs. There is no published human data.
Mechanism
Like the rest of the numbered GHRP family, GHRP-5 is a synthetic secretagogue built around the Ala-Trp-(D-Phe) aromatic core and acting at the growth hormone secretagogue receptor type 1a (GHS-R1a), the ghrelin receptor. Activation of this Gq/11-coupled receptor on anterior pituitary cells drives phospholipase C signalling, inositol trisphosphate generation and a rise in intracellular calcium, culminating in granule exocytosis. At the hypothalamus the class counteracts somatostatinergic restraint, which is why GHRPs synergise with GHRH rather than merely duplicating it. GHRP-5 adds an N-terminal tyrosine to a D-Trp-Ala-Trp-D-Phe arrangement, without the C-terminal lysine that the hexapeptides carry. In the 1981 Momany and Bowers paper this exact sequence released growth hormone from rat pituitary cells at 10-30 ng/ml of medium, roughly a thousandfold more potently than the enkephalin-derived starting compounds.
The most informative published pharmacology under the GHRP-5 label concerns lactotrophs rather than somatotrophs. In rat pituitary cell culture, GHRP-5 increased prolactin secretion, with enriched lactotroph cultures showing about 50 per cent higher secretion than controls, alongside enlarged secretory granules and cellular changes consistent with increased secretory activity. The same treatment given to intact rats produced no significant change in serum prolactin. That in vitro to in vivo discrepancy is worth taking seriously: whatever the isolated cell can do, systemic exposure at the doses used did not reproduce it, most plausibly because of clearance, restricted pituitary access or compensatory dopaminergic restraint of prolactin release in the living animal. GHS-R1a is expressed on lactotrophs as well as somatotrophs, so cross-activation of prolactin release is a class property rather than an idiosyncrasy of this analogue.
What the research shows
The primary experimental record specific to GHRP-5 is thin. Momany and Bowers reported the sequence as the most active compound of their 1981 series in rat pituitary cell culture. Two decades later, De Paul and colleagues, working in rat pituitary, reported that GHRP-5 stimulated prolactin release and prolactin messenger RNA in enriched lactotroph cultures while producing no measurable change in serum prolactin in vivo. Beyond that, GHRP-5 appears in anti-doping analytical work, including a study of adsorption losses of doping-relevant peptides during sample handling. Those analytical papers exist because GHRP-5 is on the Prohibited List, not because anyone has demonstrated it does anything useful.
There are no human studies of GHRP-5 of any design. No growth hormone response curve has been published in humans. There are no pharmacokinetic, toxicology or repeat-dose data. Claims in commercial listings that GHRP-5 promotes muscle growth, fat loss or recovery have no experimental basis in this compound; they are borrowed from the acute growth hormone data on GHRP-2 and GHRP-6, and even there the acute hormone response has never been shown to deliver those downstream outcomes in controlled trials. The one direct in vivo observation available - a null result where the cell culture result was positive - should temper rather than encourage extrapolation.
Evidence assessment
Preclinical only
Rat pituitary cell culture and whole-animal work only, and the whole-animal result for its best-documented effect was null. No human exposure has been published in any design. Preclinical is the correct tier.
Tiers are applied consistently across the library and re-checked when new trials read out. Read the grading method.
Key studies
Prolactin-releasing activity of GHRP-5 (Momany peptide) on lactotrophs in vivo and in vitro Preclinical only
In vitro, GHRP-5 significantly increased prolactin release, with enriched lactotroph cultures secreting about 50 per cent more than controls, together with enlarged secretory granules and cellular changes consistent with increased secretory activity. In vivo administration produced no change in serum prolactin.
Design, synthesis, and biological activity of peptides which release growth hormone in vitro Preclinical only
Tyr-D-Trp-Ala-Trp-D-Phe-NH2, the sequence later designated GHRP-5, was the most potent compound produced, releasing growth hormone in vitro at 10-30 ng/ml of medium and approximately 1000-fold more active than the enkephalin-derived starting compounds.
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, relating peptide conformation to potency.
Adsorption effects of the doping relevant peptides Insulin Lispro, Synachten, TB-500 and GHRP 5 Preclinical only
Peptide recovery varied by consumable material, and the authors concluded that choosing expensive low-bind consumables is not beneficial in all cases; material selection should follow the physicochemical properties of each individual peptide.
Safety
No human safety data exist. The only in vivo animal work published measured hormone concentrations rather than toxicity endpoints. Theoretical risks follow from the class pharmacology: activation of GHS-R1a is not selective for growth hormone and produces variable ACTH, cortisol and prolactin release, with appetite stimulation. The prolactin signal is worth flagging specifically for this analogue, since it is the one effect actually demonstrated in cell culture; sustained hyperprolactinaemia causes hypogonadism, galactorrhoea, menstrual disturbance and reduced libido, though whether GHRP-5 raises prolactin at all in a living human is entirely unknown, and it did not do so in intact rats. Sustained growth hormone axis stimulation carries the usual burden of fluid retention, arthralgia, carpal tunnel symptoms and impaired glucose tolerance, and is inappropriate in anyone with active malignancy or proliferative diabetic retinopathy. Material sold under this name has no pharmaceutical quality oversight; identity, purity and sterility are unverified.
Regulatory status
| Jurisdiction | Status |
|---|---|
| United Kingdom | No UK marketing authorisation. Supply for human use would amount to 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; sold only as a research chemical labelled not for human consumption. |
| WADA (sport) | Prohibited at all times, in and out of competition, under section S2.2.3 of the WADA Prohibited List, where GHRP-5 is named among the growth hormone-releasing peptides. Anti-doping laboratories have published dedicated sample-handling work on GHRP-5 as an analytical target. The draft cited section S2.1, which is incorrect. |
Questions
Because it comes from the synthetic series designed by Frank Momany and Cyril Bowers, who built the growth hormone-releasing peptide family from enkephalin-derived leads. The sequence Tyr-D-Trp-Ala-Trp-D-Phe-NH2 is reported as the most potent compound in their 1981 Endocrinology paper, and the 2002 rat prolactin study uses the 'Momany peptide' label to identify which compound it studied.
In rat pituitary cell culture, yes - the 1981 paper reports exactly that for this sequence. But no published study has measured a growth hormone response to GHRP-5 in humans, and the best-documented later animal work on it looked at prolactin rather than growth hormone.
In isolated rat lactotroph cultures GHRP-5 increased prolactin output. In living rats given the same peptide, serum prolactin did not change. The most useful reading is caution: a cell can respond to a molecule that does nothing measurable once the whole organism, its clearance mechanisms and its feedback loops are involved.
Yes, at all times. It is named among the growth hormone-releasing peptides under section S2.2.3 of the WADA Prohibited List, and anti-doping laboratories have published dedicated sample-handling studies on it as a detection target.