Ipamorelin
Research OnlyLimited EvidenceIpamorelin (NNC 26-0161)
A selective GHS-R1a agonist that triggers pulsatile growth hormone release without elevating cortisol or prolactin — the cleanest receptor profile among GH secretagogues.
A synthetic peptide that tells the pituitary gland to release a pulse of growth hormone — without affecting cortisol or other stress hormones, which is what makes it unusual compared to older GH-releasing compounds. The GH it releases is your own pituitary's GH, not injected from outside. That GH triggers IGF-1 production, which is where most of the downstream effects (tissue repair, body composition changes) would come from, if they occur. The key word is "if": the only human clinical trial ever run with ipamorelin was for a gut motility problem after surgery, and it didn't work. No human trial has ever directly tested what the community uses it for — muscle, fat loss, recovery. That mechanism may still work; it just hasn't been tested the way you'd need to be confident about it.
Half-Life
~2 hours (subcutaneous; confirmed in human PK/PD study, Gobburu et al. 1999)
Molecular Weight
711.85 g/mol
Ipamorelin is a synthetic pentapeptide developed by Novo Nordisk and characterized in 1998 as the first GH secretagogue to achieve selective GH release without meaningfully elevating cortisol, prolactin, or ACTH. It acts as an agonist at the GHS-R1a (ghrelin receptor) on pituitary somatotrophs, triggering endogenous GH pulses. Human pharmacokinetic data exists — a 1999 dose-escalation study in healthy male volunteers characterized its 2-hour half-life and dose-proportional GH response. The only completed human efficacy trial (Beck et al. 2014) tested ipamorelin for postoperative ileus and failed its primary endpoint. For the applications the community uses it for — body composition, GH axis optimization, recovery — no published human trial evidence exists. Evidence for those endpoints is entirely inferred from the GH response, which is real; translation to clinical outcomes in healthy adults is assumed, not demonstrated.
Also Known As
Amino Acid Sequence
Aib-His-D-2-Nal-D-Phe-Lys-NH₂
Reconstitution
Reconstitute with bacteriostatic water. Typical concentration: 1–2 mg/mL.
Open Reconstitution Calculator →