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Pentapeptide secretagogue · selective at GHS-R1a
A selective growth hormone secretagogue and ghrelin receptor agonist pentapeptide. Supplied as a lyophilized powder for research purposes only.
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Tested lot by lot at ≥99% purity. The Janoshik certificate for your lot is emailed with the order.
Everything Valtrax Research ships is bench material for in-vitro work. None of it is a drug, a supplement, a cosmetic, or a medical device, and none of it is intended for human or animal use, ingestion, or administration. Placing an order is your confirmation that you are a qualified researcher buying for lawful research, under every Canadian law and regulation that applies to you.
Aib-His-D-2Nal-D-Phe-Lys — five residues, with the non-natural Aib and the two D-amino acids carrying the load that keeps it intact. Ipamorelin is a growth-hormone secretagogue: it agonizes the ghrelin receptor (GHS-R1a) on pituitary somatotrophs to trigger GH release, copying ghrelin’s GH effect while leaving ghrelin’s appetite drive behind.
Its standing rests on a negative result. Raun’s founding work showed it raised GH cleanly, with no cortisol or prolactin spillover of the kind that compromised earlier secretagogues — and that clean profile is exactly why it endures as a reference GHS on the bench.
Selectivity is the finding the literature keeps returning to — GH release with little to no movement in cortisol or prolactin, established by Raun and treated since as ipamorelin’s signature. Built around it are the GH/IGF-1 output measurements, Johansen’s rat bone-growth line, and PK/PD modeling that ties stimulus to response.
Ipamorelin serves as a clean probe of the ghrelin-receptor branch of GH control. Bound to GHS-R1a on somatotrophs, it drives growth-hormone release; because its selectivity for that receptor is high, the GH signal arrives largely decoupled from the rest of the pituitary output.
That decoupling is the utility. Ghrelin itself drags appetite and wider endocrine effects into any experiment, whereas ipamorelin lets a lab ask the narrower question — what the GHS-R1a signal on its own does to GH, and through GH to IGF-1.
Ipamorelin emerged from a targeted program at Novo Nordisk aimed at a growth-hormone secretagogue that would hit the receptor without the off-target activity of the preceding GHRP-class peptides. Raun’s 1998 report put it forward as the first genuinely selective GHS.
Later work — Johansen’s longitudinal bone-growth study in rats, then PK/PD modeling in human volunteers — rounded out its profile, and the pentapeptide settled in as a standard tool for ghrelin-receptor research.
In vitro and animal studies
Ipamorelin is a synthetic pentapeptide agonist at the growth hormone secretagogue receptor, the same receptor targeted by the endogenous hormone ghrelin. It was developed at Novo Nordisk and characterised in a body of preclinical work whose defining finding was selectivity.
Earlier growth hormone secretagogues raised GH but also raised cortisol, prolactin and ACTH, because the receptor system interacts with several pituitary outputs. The published characterisation of ipamorelin reported GH release with markedly less effect on those other hormones than comparator secretagogues produced at equivalent GH response. That selectivity is the compound's principal claim to research interest and is reasonably well supported in the animal literature.
Additional preclinical work covered bone: studies in rodents reported effects on bone mineral content and longitudinal growth consistent with GH axis stimulation. Work on gastrointestinal motility followed from the ghrelin receptor's role in gut function, and that line of research became the basis for the compound's later clinical development.
A detail from the original characterisation is worth noting because it explains the compound's reputation. Ipamorelin was profiled alongside GHRP-6 and other secretagogues in the same experimental series, and the comparison was direct rather than inferred across studies — which is why the selectivity claim is better founded than most head-to-head assertions in this field.
Its pentapeptide structure, incorporating unnatural amino acid residues including Aib, was designed to hold the conformation required for receptor binding while resisting proteolysis. That conformational constraint appears to be what produces the selectivity: the molecule engages the growth hormone secretagogue receptor in a way that favours the GH-release pathway over the signalling that drives ACTH and prolactin output.
Human data, where it exists
Ipamorelin did enter human clinical trials, which distinguishes it from most secretagogues sold as research chemicals. Helsinn Therapeutics developed it for postoperative ileus — the delayed return of bowel function after abdominal surgery — on the strength of the ghrelin receptor's prokinetic role rather than its GH effects.
Those trials did not succeed. The programme failed to meet its primary endpoints, and development was discontinued. Ipamorelin holds no marketing approval from any regulatory authority for any indication.
This produces an evidence profile worth being precise about: there is genuine human exposure data from a real clinical programme, including safety information gathered under trial conditions, and there is a negative efficacy result for the indication studied. There is no human trial evidence for the body-composition and recovery uses the compound is marketed around, and no long-term human safety dataset at the exposures commonly discussed.
Common assertions, and what the record supports
The claim that ipamorelin is the selective secretagogue — raising GH without meaningfully raising cortisol and prolactin — is the best-supported claim attached to it, and it comes from the preclinical characterisation rather than from marketing.
What that selectivity does not do is remove the consequences of GH elevation itself. Avoiding a cortisol rise is a genuine advantage over GHRP-2 or GHRP-6; it does not make sustained GH and IGF-1 stimulation neutral. The claim frequently slides from selective to safe, and those are different propositions.
A second claim presents the failed ileus trials as irrelevant because the indication differed. The efficacy result is indeed specific to that indication, but the human safety data gathered in those trials is some of the only human data that exists for this compound, and it should be counted rather than discarded.
Against the compounds it is most often confused with
Against GHRP-2, ipamorelin is the more selective of the two ghrelin-receptor agonists. Both raise GH; GHRP-2 produces a stronger GH response but also measurable increases in cortisol and prolactin, while ipamorelin's published profile shows substantially less of that. Which is preferable depends on whether the experiment tolerates confounding from other pituitary outputs.
Against CJC-1295 in either form, the difference is receptor system: GHRH receptor versus growth hormone secretagogue receptor. The two are complementary rather than competing, and combined stimulation has been reported to produce a greater GH response than either alone — the reason the pairing is conventional in this literature.
Against tesamorelin, the contrast is developmental rather than mechanistic: tesamorelin is an approved drug with completed trials for a defined indication, ipamorelin a discontinued candidate with a negative trial result.
Adverse findings, toxicology gaps, material hazards
GH axis stimulation carries a consistent set of documented effects: insulin resistance and impaired glucose tolerance, fluid retention, arthralgia, and carpal tunnel symptoms. Selectivity for GH over cortisol and prolactin does not alter any of these, because they follow from GH itself.
Sustained IGF-1 elevation raises the mitogenic concern that applies across this shelf. IGF-1 promotes cell proliferation and inhibits apoptosis, and epidemiological work has associated elevated IGF-1 with increased risk of several cancers. No study has characterised what repeated secretagogue-driven IGF-1 elevation does over years.
Ghrelin receptor agonism affects appetite and gastric motility, which is a predictable pharmacological consequence rather than an adverse event as such, but it is frequently unmentioned.
The compound is covered by the World Anti-Doping Agency Prohibited List under S2. Long-term human safety at the exposures discussed is uncharacterised.
Bench practice for this compound
Ipamorelin is a pentapeptide, short and relatively stable, and it dissolves readily. Introduce bacteriostatic water against the vial wall rather than onto the cake, and swirl gently rather than shaking.
Store reconstituted solutions at 2–8 °C protected from light, and observe the working window given on this page. Unopened lyophilized powder kept frozen is stable considerably longer. Aliquot before freezing if a vial will be drawn on more than once, since repeated freeze-thaw cycling is the most common avoidable cause of degradation.
This summary describes published research. It is not a protocol, not a recommendation, and not a statement that this compound is safe or effective for any use. Not for human or animal use.
Raun, K. et al. (1998). Ipamorelin, the first selective growth hormone secretagogue.
PubMedJohansen, P.B. et al. (1999). Ipamorelin, a new growth-hormone-releasing peptide, induces longitudinal bone growth in rats.
PubMedGobburu, J.V.S. et al. (1999). Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers.
PubMedEvery lot is tested for identity, purity, and net content.
Janoshik Analytical, a laboratory Valtrax does not own, runs the testing — identity by mass spectrometry, purity by RP-HPLC at ≥99%, on the lot you receive.
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