Ipamorelin
Also known as: NNC 26-0161
A selective growth-hormone secretagogue that raises GH without spiking cortisol or prolactin — but its clinical benefits are unproven and it is sold only as a research chemical.
Not approved by the FDA for any use. Developed as an investigational drug but never brought to market after early-stage trials; now sold for laboratory research only. Often paired with CJC-1295 in research-chemical stacks.
What it is
Ipamorelin is a synthetic pentapeptide growth-hormone secretagogue. It mimics the hormone ghrelin at the growth-hormone secretagogue receptor (GHS-R1a) and triggers the pituitary to release GH. Its distinguishing feature, established when it was first characterized in 1998, is selectivity: it raises GH while leaving cortisol, ACTH, and prolactin largely untouched — cleaner in that respect than older growth-hormone-releasing peptides. It works by a different mechanism than GHRH analogs like CJC-1295, which is why the two are often combined in research-chemical stacks.
What it’s approved or studied for
Nothing is approved. Ipamorelin was carried into early clinical development — most notably for post-operative ileus — but was not brought to market, and it is now sold only as a research chemical. It is not FDA-approved for any use.
What human evidence exists
Human data are limited. Small pharmacology studies support the core biomarker effect: ipamorelin raises GH selectively (Grade C). The one rigorous clinical indication it was tested for, post-operative ileus, did not succeed, and development stopped (Grade E). The popular uses — fat loss, muscle, recovery, anti-aging — have no controlled human outcome evidence and are Grade U. Most of the broader supporting data are from animal models.
The major unknowns
Whether ipamorelin produces any meaningful body-composition or performance benefit in humans is unknown, as is the long-term safety of repeatedly stimulating GH release (Grade U). As a research chemical, purity and dosing are uncontrolled, and the common practice of stacking it with CJC-1295 has never been studied for safety or efficacy.
Most important safety considerations
There are no controlled long-term human safety data, so the honest answer on safety is that it is not established. Repeated GH/IGF-1 stimulation carries theoretical concern, particularly with any existing malignancy. The product is unregulated, prohibited in sport under WADA’s S2 category, and not a legal therapeutic. This page summarizes the research record; it is not medical advice or an endorsement of use.
Evidence by outcome
Each outcome is graded on its own evidence — a compound can be strong for one use and unproven for another. See how we grade.
A selective, measurable biomarker effect with limited human PK/PD data. — Ipamorelin activates the ghrelin receptor (GHS-R1a) and raises GH while largely preserving the natural pulsatile pattern and, unlike some GHRPs, without meaningfully raising ACTH, cortisol, or prolactin. Human evidence is limited to small pharmacology studies.
Tested in a randomized trial and did not succeed; development was halted. — This was the compound's most rigorous human indication. A phase-2 program in post-operative ileus did not lead to approval, and clinical development was discontinued.
Unknown — no human outcome trials. — Widely marketed for recomposition, usually stacked with CJC-1295, but no randomized human trial has tested body-composition endpoints.
Unknown — extrapolated from the GH effect, not demonstrated.
Unknown — no long-term human safety data exist.
Safety
Common adverse effects
- Injection-site reactions
- Headache
- Flushing
- Transient hunger (ghrelin-receptor mediated)
Serious risks
- Uncertain long-term effects of repeated GH stimulation
- Unregulated product purity and contamination risk
- No controlled long-term human safety data
Contraindications
- Not approved for human use; no human contraindication data; theoretical concern with active malignancy given GH/IGF-1 stimulation
References