# Ipamorelin: The Selective GH Secretagogue, Research Summarized > Ipamorelin releases a clean pulse of growth hormone (GH) without raising cortisol or prolactin. A plain-English digest of the published research on the GH axis, every claim cited. A plain-English digest of what the published studies on the growth-hormone axis actually measured, from the 1998 founding paper to the 2024 animal work, with every quantitative claim cited. ## The short version Ipamorelin is a small lab-made peptide — a chain of just five amino-acid building blocks. Its one job is to tell the pituitary gland (a pea-sized gland at the base of the brain) to release a short burst of growth hormone, or GH. What made it notable when it was first described in 1998 is *selectivity*: it nudges GH up without also raising stress hormones like cortisol and prolactin, which the older peptides in its family did [1]. People in research-use communities pair it with related peptides and report better sleep and faster recovery — but those are personal accounts, not proof, and what people report (including the downsides) is laid out plainly on [the effects page](/effects). The honest state of the science: the animal data is consistent, the single human trial that tested whether it *treats* anything failed [3], and it has never been approved as a drug anywhere. This site reads the published record and cites every number. ## What "ipamorelin" actually is Ipamorelin (sequence Aib-His-D-2-Nal-D-Phe-Lys-NH2) is a wholly synthetic pentapeptide — five amino acids strung together in a lab, never found in the human body. It works by mimicking ghrelin, the hormone your gut releases when you are hungry, at a docking site on pituitary cells called the GHS-R1a receptor (the "growth hormone secretagogue receptor") [1]. When ipamorelin docks there, the cell fires off a pulse of growth hormone. That is the entire mechanism. It belongs to a family called growth-hormone-releasing peptides, or GHRPs, and it was engineered from an earlier member (GHRP-1) by trimming two amino acids out of the middle [1]. A note on the domain name: "script" is slang for a prescription, but ipamorelin is **not** a prescribable, approved medicine. No doctor can write a script for an approved ipamorelin product, because no regulator has ever approved one. This is a [Ipamorelin research](/research) digest, not a clinic and not a pharmacy. ## The signature finding: a GH pulse, and nothing else In the 1998 founding study, ipamorelin released GH as potently as the older peptide GHRP-6 in rat pituitary cells, anaesthetised rats, and conscious pigs (pig ED50 = 2.3 nmol/kg, versus 3.9 nmol/kg for GHRP-6) — yet it did **not** raise the stress hormones ACTH or cortisol above baseline, even at doses more than 200 times higher than the dose needed to release GH [1]. That clean separation is its defining trait and the reason it is still studied a quarter-century later. Downstream of that GH pulse sits IGF-1 (insulin-like growth factor 1), a liver-made messenger that carries out many of GH's longer-term effects. Importantly, IGF-1 was **not** reliably raised in the short rodent studies — a 15-day rat bone-growth study increased the bone growth rate without any measurable change in total IGF-1 [4]. The pulse is real; whether it sustains into a lasting IGF-1 rise depends on the protocol, and that nuance is covered in [how it works](/how-it-works). ## What the human evidence shows — and where it stops Human data is thin and, for treating disease, largely negative. A pharmacology study in eight healthy men per dose level mapped its kinetics cleanly: dose-proportional, a terminal half-life of roughly 2 hours, and a single GH pulse peaking about 40 minutes after dosing [2]. That is solid, but it only describes how the body handles the peptide — not whether it helps anyone. The one trial that tested benefit was a Phase 2 study in 114 patients recovering from bowel surgery. It **missed** its main goal: time to the first tolerated meal was 25.3 hours with ipamorelin versus 32.6 hours with placebo, a difference that could have been chance (p=0.15) [3]. After that, clinical development stopped. The most recent published work is animal research — a 2024 ferret study where ipamorelin cut chemotherapy-driven weight loss by about 24% but had no anti-nausea effect [5]. That is the real shape of the evidence: a well-characterised mechanism, a clean pulse, and an unfinished clinical story. ## How to read this site Every page leads with the finding and cites it. [Research](/research) covers the mechanism, the key studies, and the CJC-1295 combination. [How it works](/how-it-works) walks through the GH-axis biology in plain English and compares ipamorelin with sermorelin and tesamorelin. [Benefits](/benefits) collects what the studies and the research-use community report. [Effects](/effects) is the honest accounting — upsides, downsides, and who has a reason to be cautious. Dosing pages describe only what was given to which species in which study; this site never tells a person to take anything. The full citation list, with DOIs and PubMed links, lives on [Ipamorelin references](/references). --- A plain-English digest of the ipamorelin research — the GH-axis findings explained and cited, with no clinic, no pharmacy, and no prescription behind it.