IpamorelinWhat the studies show
A five-amino-acid ghrelin mimetic built at Novo Nordisk to release growth hormone without the cortisol rise of the older GHRPs.
5 min read · Small human studies · Updated November 2026
In short
- Name
- ipamorelin (sold by Progression Labs as Ipamorelin)
- Evidence
- Small human studies
- Bottom line
- Animal pharmacology from one company, a human pharmacokinetic study, and a single 114-patient placebo-controlled trial for a surgical complication that did not meet its endpoint; nothing in people on the uses the peptide is usually discussed for.
Before you read this
This guide explains what published studies found. That is all it is.
It is not medical advice and it is not instructions for using anything. Where a dose appears, we are reporting what a named study gave the people or animals in it — a fact about the study, not an instruction to you.
The compounds here are not approved by the FDA for use in people and are sold for laboratory research only. A study tells you what happened to the subjects in it; it does not tell you what would happen to you. Talk to a doctor first.
What it is
Ipamorelin is a chain of five amino acids, two of them in the mirror-image D form, designed in the 1990s at Novo Nordisk in Denmark 1. It belongs to the family of growth hormone releasing peptides (GHRPs) that began with GHRP-6, and like the rest of that family it works on the ghrelin receptor in the pituitary and hypothalamus rather than on the receptor for growth hormone releasing hormone. The 1998 paper that introduced it called it "the first selective growth hormone secretagogue" because, in the animals tested, it released growth hormone but not the stress hormones that GHRP-6 and GHRP-2 also release 1.
The studies below call this molecule ipamorelin. Progression Labs sells it as Ipamorelin; the guide uses the store's name and the papers use theirs.
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Why "selective" mattered
In the 1998 study, ipamorelin released growth hormone from rat pituitary cells in a dish and from live pigs with about the same potency as GHRP-6 1. The difference showed up in what else came out. GHRP-6 and GHRP-2 also raised ACTH and cortisol in the pigs; ipamorelin did not, even at doses far above the ones needed for a full growth hormone response 1. That was the point of the molecule: the older peptides pulled a stress-hormone response along with the growth hormone one, and this one did not, at least in pigs.
A 1999 study in human volunteers gave ipamorelin by vein and modelled the result. Growth hormone rose within minutes and the size of the pulse tracked the dose, and the authors built a pharmacokinetic model from the data 2. That study measured a hormone response, not a clinical outcome.
Bone in rats
A 1999 study from the same Novo Nordisk group gave ipamorelin to young rats for two weeks and measured how much the tibia had lengthened. The rats given ipamorelin grew longer bones than the controls, and the effect was in the same range as growth hormone itself at the doses tested 3. The same paper reported the expected rise in body weight. These are growing rats; the study says nothing about adult bone.
The surgical trial
The one controlled human trial was not about growth hormone at all. Ghrelin speeds up the stomach and bowel, so an Italian company, Helsinn, tested ipamorelin for postoperative ileus, the stalled gut that follows abdominal surgery. In rats with surgically induced ileus, ipamorelin restored gut movement 4. The human phase 2 trial, published in 2014, randomised 114 patients who had just had part of the bowel removed to ipamorelin at 0.03 mg per kilogram by vein twice a day or to placebo, and timed how long it took each patient to tolerate a first meal 5.
The result: ipamorelin was well tolerated, but the difference from placebo in the primary endpoint was not statistically significant 5. The drug did not go on to approval for that use or for any other. For a guide like this, that trial is still the most useful document that exists, because it is the only placebo-controlled record of what ipamorelin did in a group of people.
What is not known
There is no published trial of ipamorelin for body composition, strength, sleep, recovery or ageing in people, and no study of what happens to the growth hormone response over months of repeated dosing. The selectivity finding comes from pigs; the human data are a volunteer pharmacokinetic study and a surgical trial that measured gut function. Nor is there any human measurement of the thing the peptide is named for: no published study has checked whether the pig finding, growth hormone without cortisol, holds in people. Ipamorelin is not an approved drug anywhere.
What these studies are, and aren't
Small human studies. Animal pharmacology from one company, a human pharmacokinetic study, and a single 114-patient placebo-controlled trial for a surgical complication that did not meet its endpoint; nothing in people on the uses the peptide is usually discussed for.
Sources
- 1Raun K et al. Ipamorelin, the first selective growth hormone secretagogue. European Journal of Endocrinology, 1998.
- 2Gobburu JV et al. Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers. Pharmaceutical Research, 1999.
- 3Johansen PB et al. Ipamorelin, a new growth-hormone-releasing peptide, induces longitudinal bone growth in rats. Growth Hormone & IGF Research, 1999.
- 4Venkova K et al. Efficacy of ipamorelin, a novel ghrelin mimetic, in a rodent model of postoperative ileus. Journal of Pharmacology and Experimental Therapeutics, 2009.
- 5Beck DE et al. Prospective, randomized, controlled, proof-of-concept study of the ghrelin mimetic ipamorelin for the management of postoperative ileus in bowel resection patients. International Journal of Colorectal Disease, 2014.
More in Growth hormone axis
- CJC-1295 (no DAC): What the Studies ShowSermorelin with four amino acids swapped to survive the blood longer, and without the albumin-binding tail that gave the DAC version its week-long half-life.
- CJC-1295 + Ipamorelin: What the Studies ShowTwo peptides for two receptors on the same pituitary cell. The idea comes from a 1990 study in men; the pair itself has never been tested together.
- CJC-1295 with DAC: What the Studies ShowA GHRH analogue that bonds to albumin in the blood: one injection raised growth hormone for about a week in healthy adults, with the normal pulses intact.
- GHRP-2: What the Studies ShowThe potent GHRP approved in Japan as a one-dose test for growth hormone deficiency, and shown to make healthy men eat about a third more at a single meal.
- GHRP-6: What the Studies ShowThe 1984 hexapeptide that came before its own receptor and before ghrelin — and the reason the hunger it causes is the receptor doing its job.