// the basics
What Is Ipamorelin? The Peptide Explained
Five amino acids, one receptor, one defining trait: it pulses growth hormone without raising cortisol. Structure, mechanism, history, and legal status.
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What is ipamorelin peptide, in plain terms? It is a lab-made chain of five amino acids (a pentapeptide) that mimics the body's hunger hormone, ghrelin, at one specific docking site — the ghrelin receptor on the pituitary gland. When it docks, the pituitary releases a pulse of growth hormone.
Its one famous feature is selectivity. Older peptides that did this same job also raised the stress hormone cortisol and the hormone prolactin. Ipamorelin does not, even at very high doses [4]. That clean profile is why it was called the first selective growth hormone secretagogue. It is wholly synthetic — not something the human body makes. It was never approved as a medicine. And despite the word "store" appearing in some domain names, this page sells nothing; it explains the molecule.
The molecule, by the numbers
Ipamorelin is a synthetic pentapeptide, sequence Aib-His-D-2-Nal-D-Phe-Lys-NH2. (Aib = alpha-aminoisobutyric acid, a non-natural amino acid at position 1; the D-form amino acids resist enzyme breakdown.) Molecular formula C38H49N9O5, molecular weight about 711.9 Da, CAS number 170851-70-4. It was derived from the earlier peptide GHRP-1 by removing a central two-amino-acid segment.
Its development code was NNC 26-0161. It is also called ipamorelin acetate (the salt form). It is a selective agonist of GHS-R1a — the growth hormone secretagogue receptor, which is also the ghrelin receptor. That single receptor is the whole mechanism.
What it does in the body
Ipamorelin binds GHS-R1a on the pituitary's somatotrophs (growth-hormone cells), sets off a calcium-driven signaling cascade, and triggers a pulse of growth hormone [4]. The pulse is discrete — in humans it peaks near 40 minutes after dosing and clears with a half-life of about 2 hours [6].
The selectivity is the headline: potent growth-hormone release, but no meaningful rise in ACTH, cortisol, or prolactin even past 200-fold the growth-hormone ED50, shown in rats and pigs [4]. Downstream, growth hormone can raise IGF-1 — though in short rat studies, bone grew without a measurable IGF-1 bump [1]. The receptor also sits on gut neurons and pancreatic cells, which is why ipamorelin has separate, growth-hormone-independent effects on gut motility and insulin in preclinical work.
Where it came from
Ipamorelin was developed by a pharmaceutical company in the 1990s and characterized in 1998 as the first highly selective growth hormone secretagogue [4]. Human pharmacokinetics were mapped in 1999 in healthy male volunteers [6]. It was then advanced for postoperative ileus — slowed bowel function after surgery — the only indication that reached Phase 2 testing.
That trial (114 bowel-resection patients) missed its primary endpoint in 2014, and no further clinical development followed [5]. From discovery to a stalled Phase 2, that is the arc. It never became a drug.
Is ipamorelin fda approved
No. Ipamorelin is not FDA-approved as a drug for any indication, and it is not approved by any other regulator either. It was investigated — notably for postoperative ileus (NCT00672074) — but never approved, and that trial failed its primary endpoint [5]. In 2024 the FDA removed ipamorelin acetate from Category 2 of the interim Section 503A bulk drug substances list and reviewed it at the October 29, 2024 Pharmacy Compounding Advisory Committee meeting; it is not an approved bulk substance for compounding. It is marketed only as a research chemical. It is also prohibited in sport at all times under the WADA list (category S2) and is detectable in urine.
What it is not
Ipamorelin is not the same as the cjc-1295 ipamorelin combination — that pairs ipamorelin with a separate GHRH analog, and this page is about pure ipamorelin. It is not a GHRH analog itself (those are sermorelin, tesamorelin, CJC-1295). It is not an approved medicine, not a fat-loss drug with human outcome data, and not a product sold here. It is a research peptide with a strong preclinical bone record [1][2][3], a clean selectivity profile [4], and a thin, mostly negative human file [5][6].