Ipamorelin
Ipamorelin — evidence, development history & status

Class: peptide
Synonyms: Ipamorelin
Novo Nordisk code NNC 26-0161
CAS 170851-70-4
sequence Aib-His-D-2-Nal-D-Phe-Lys-NH₂. INCI: none
Function tags: GH secretagogue / ghrelin-receptor agonist
body composition (research context)
Overall evidence grade: B
WADA prohibited: yes
WADA note: Sport: WADA-prohibited at all times — GH secretagogues / GHRPs fall under Section S2.2.
Last updated: 2026-07-11

In brief: Ipamorelin is a selective ghrelin-receptor agonist that raises GH in a clean pulse (without the cortisol/prolactin rise of older GHRPs) — a real and well-characterised pharmacology. But its only rigorously tested indication (postoperative ileus) failed its primary endpoint, it is not approved anywhere, and its popular anti-aging / fat-loss / muscle use has never been tested in humans. Banned in sport.

## Identity a synthetic **pentapeptide** (5 amino acids, < 40 aa → peptide), a **selective agonist of the ghrelin / growth-hormone-secretagogue receptor (GHS-R1a)**. Derived from **GHRP-1** by removing its central Ala-Trp dipeptide — the change that preserved GH-releasing potency while sharply improving **selectivity**. MW ≈ 712 Da. ## Development & history - Developed by **Novo Nordisk A/S** (Denmark), mid–late 1990s, out of a medicinal-chemistry programme seeking a GH secretagogue with fewer off-target effects.
- First characterised by **Raun et al. 1998** (*European Journal of Endocrinology*) as **"the first selective growth-hormone secretagogue"** — releasing GH without the ACTH/cortisol/prolactin/FSH/LH/TSH elevations seen with older GHRPs (GHRP-6, GHRP-2, hexarelin), even far above the GH-release dose.
- Later **licensed by Helsinn Therapeutics** and developed for a specific medical use: **postoperative ileus** (gut-motility recovery after abdominal surgery).
- **Phase 2 RCT** (Beck et al. 2014, *Int J Colorectal Dis*, n=87) — the most rigorous published human study — **did not meet its primary endpoint**; not advanced to Phase 3.
- Never given a brand name, **never approved** for any indication; migrated to functional-medicine / gray-market use. ## Mechanism (as proposed) binds **GHS-R1a** (the ghrelin receptor) on pituitary somatotrophs → Gq/phospholipase-C → IP₃/calcium release → **pulsatile GH** secretion, mimicking ghrelin — but, distinctively, without meaningfully activating the ACTH/cortisol or prolactin axes.

Evidence grades by outcome:
outcome: Selective GH release (no cortisol/prolactin) in humans
grade: B
base: Raun 1998 + human PK studies
effect: Clean, selective GH pulse
caveat: Selectivity + GH release are genuine; this is not the same as clinical benefit
outcome: Clinical efficacy (postoperative ileus — the only tested indication)
grade: D
base: Phase 2 RCT (Beck 2014, n=87)
effect: Failed primary endpoint
caveat: The single rigorous human trial did not work
outcome: Anti-aging / fat loss / muscle (the popular use)
grade: F
base: None in humans
effect: Not demonstrated
caveat: Never tested in humans for these goals — "selectivity is real, efficacy for body composition is untested"
outcome: Safety
base: Well tolerated in the POI trials; no long-term data
effect: Generally tolerated
caveat: No long-term human data; GH/IGF-1 elevation carries theoretical risks; WADA-banned

Legal status:
region: EU
status: Not approved
note: Not approved; not eligible for magistral/officinal compounding.
region: US
status: Not FDA-approved (503A Cat. 2)
note: Placed in 503A Category 2 (2023); status in flux amid the 2026 reclassification, but not among the seven peptides in the specific July 23–24 2026 PCAC review; not FDA-approved.
region: INT
status: Not approved
note: Not approved.

Cosmetic claims:

Note: Research / reference — not for sale. No dosing, reconstitution, or administration is published (intentional). Neutral scientific reference only.

Sources:
Raun K, et al. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol. 1998. (PMID 9849822)
Beck DE, et al. (Phase 2 RCT of ipamorelin for postoperative ileus.) Int J Colorectal Dis. 2014. (PMID 25331030)
Ishida J, et al. Growth hormone secretagogues: history, mechanism of action, and clinical development. JCSM Rapid Commun. 2020.