# Ipamorelin: An Evidence Appraisal of the Published Research > Ipamorelin is a selective growth hormone secretagogue with a large marketing footprint and a thin evidence base. We weigh what the published record actually shows — including its one failed human trial. A precise, plain-English read of the peer-reviewed record: what the founding pharmacology proved, where the one human trial failed, and what the anti-doping labs can already detect — with every claim weighed and cited. ## The short version Ipamorelin is a lab-made peptide — a short chain of five amino acids — that tells the pituitary gland (a pea-sized gland under the brain) to release a pulse of growth hormone. Its one standout trait, proven in its first study, is **selectivity**: it raises growth hormone without spiking stress hormones like cortisol, the way older peptides of its type did. That clean profile is real and well documented. What is *not* well documented is almost everything the marketing promises. The drug has never been approved anywhere. Its only finished human trial — for sluggish bowels after surgery — did not work. Most of what you read about fat loss, muscle, and "anti-aging" rests on mechanism and a handful of short animal studies, not on results in people. This site reads the actual record straight, weighs how strong each piece of evidence is, and — including the downsides — is honest about [Ipamorelin effects](/effects). For sports testing, note that anti-doping labs can already detect it. ## What the founding science actually established Ipamorelin's reputation begins with one finding, and it holds up. In its 1998 characterization, ipamorelin (sequence Aib-His-D-2-Nal-D-Phe-Lys-NH2) released growth hormone potently in rat pituitary cells, anaesthetised rats, and conscious pigs — with a swine ED50 of 2.3 nmol/kg, slightly more potent than the older peptide GHRP-6 at 3.9 nmol/kg [1]. The headline result was not the potency but the **selectivity**: even at doses more than 200 times its growth-hormone ED50, ipamorelin did not raise ACTH or cortisol (stress hormones) above the level seen with growth-hormone-releasing hormone itself [1]. That made it, in the authors' framing, the first highly selective growth hormone secretagogue (a compound that prompts the pituitary to secrete growth hormone). This is the strongest, most reproducible claim in the entire ipamorelin literature — and it is worth stating plainly because so much of what follows is weaker. Selectivity is a property of the molecule. It is not, by itself, evidence that the molecule does anything useful for a person. ## Where the evidence thins — and where it failed Move past the founding pharmacology and the record gets sparse fast. The human pharmacokinetic data amount to a single study in eight men per dose level, which pinned the terminal half-life at roughly **2 hours** and showed a single growth-hormone pulse peaking about 40 minutes after dosing [2]. That is good, clean data — and it is nearly the whole of the human PK record. The one published Phase 2 trial is the appraisal's pivot point. In 114 adults recovering from bowel surgery, intravenous ipamorelin **missed its primary endpoint**: median time to the first tolerated meal was 25.3 hours with ipamorelin versus 32.6 hours with placebo, a difference that did not reach statistical significance (p=0.15) [3]. The drug was not unsafe in that short window, but it did not work for the indication it was tested in, and no further clinical program followed. Everything sold today is sold past that result, not because of it. ## What the rodent studies add — and the safety signal that frames them Animal work is where ipamorelin's more flattering numbers come from, and they are genuinely interesting. Subcutaneous ipamorelin dose-dependently raised the longitudinal bone-growth rate in adult rats, from 42 to 52 microns per day at the top dose — notably *without* a measurable rise in circulating IGF-1, suggesting a partly local, pulse-driven effect [4]. The most recent in-vivo study, a 2024 ferret model, found ipamorelin cut chemotherapy-driven weight loss by about 24% through a peripheral mechanism, though it had no anti-nausea effect [5]. The sober counterweight: a 28-day study of a *different* compound in the same receptor class found dose-dependent heart-muscle damage in rats [6]. Ipamorelin itself was not the tested compound, and no equivalent long-term cardiovascular study of ipamorelin exists in any species — which is exactly the point. The class carries a signal; ipamorelin's long-term safety in humans is simply uncharacterized. ## The anti-doping lens: detection has already caught up If there is one corner of the ipamorelin literature that is mature, it is the anti-doping science — and it cuts against the assumption that a research peptide flies under the radar. Ipamorelin and other growth hormone secretagogues are prohibited in sport at all times under the World Anti-Doping Agency's category S2 [7]. Detection methods are well established and still advancing. A direct-urine-injection method using liquid chromatography and ion-mobility mass spectrometry detects ipamorelin alongside 17 other prohibited small peptides at limits of detection of 50-500 pg/mL [9]. A comprehensive metabolism study mapped at least three urinary ipamorelin metabolites, building the database labs screen against [11]. And when Danish customs seized doping material, analysts found not plain ipamorelin but a glycine-modified analogue of it — evidence that even designer variants are being identified [7]. The marketing rarely mentions any of this. The literature is unambiguous: this is a detectable compound. The full reading list is on the [Ipamorelin references](/references). --- An evidence-appraisal reading of the Ipamorelin record — the founding selectivity data weighed against the failed Phase 2 trial and the marketing, with the anti-doping detection science laid out plainly; no clinic behind the appraisal and nothing here dosed, dispensed, or sold.