A selective GH secretagogue that mimics ghrelin at GHS-R. Structurally it is Synthetic pentapeptide GH secretagogue (GHRP).

How strong is the evidence for Ipamorelin?

PeptideHormone grades Ipamorelin at the "Preclinical" evidence tier — the evidence is largely animal or in-vitro, with human data thin or absent. It is catalogued as an engineered analog built on an endogenous hormone, and the tier is an editorial judgment about the public literature that can change as the science does.

What is the half-life of Ipamorelin?

The reported circulating half-life of Ipamorelin is ~2 h.

Ipamorelin

A selective GH secretagogue that mimics ghrelin at GHS-R.

AnalogPreclinicalBased on GhrelinCompare with Ghrelin Compare lineage

Selectivity as the design goal: the ghrelin receptor spoken to precisely, to see what the hunger signal does when isolated from hunger.

Identity

Class: Synthetic pentapeptide GH secretagogue (GHRP)
Source: Synthetic ghrelin-receptor agonist
Receptor: Growth hormone secretagogue receptor (GHS-R1a)

Key properties

Evidence floorClinicalREF1CLIN1

Molecular weight

~711.9 Da

REF

Half-life (native)

~2 h

CLIN

Model dosing

Approximate values for the native hormone; engineered analogs are often deliberately larger and far longer-acting. Each figure carries its own provenance tier, and the floor is the weakest of them - the Standard.

Mechanism

Ipamorelin is a synthetic pentapeptide that activates the ghrelin receptor GHS-R1a to trigger GH release, working through the secretagogue pathway rather than the GHRH receptor. It was engineered for selectivity — releasing GH with little effect on cortisol or prolactin, unlike earlier GHRPs — which is why it is often paired with a GHRH analog for additive, still-pulsatile GH output.

Reference notes

Introduced as 'the first selective growth hormone secretagogue' — its calling card is minimal cortisol and prolactin release.
Foundational efficacy data are largely preclinical (rodent); it was trialed in humans for postoperative ileus, but development was discontinued.
Its GHS-R pathway is synergistic with GHRH analogs because the two act on different receptors.

Common questions

What is Ipamorelin?: A selective GH secretagogue that mimics ghrelin at GHS-R. Structurally it is Synthetic pentapeptide GH secretagogue (GHRP).
How does Ipamorelin work?: Ipamorelin is a synthetic pentapeptide that activates the ghrelin receptor GHS-R1a to trigger GH release, working through the secretagogue pathway rather than the GHRH receptor. It was engineered for selectivity — releasing GH with little effect on cortisol or prolactin, unlike earlier GHRPs — which is why it is often paired with a GHRH analog for additive, still-pulsatile GH output.
How strong is the evidence for Ipamorelin?: PeptideHormone grades Ipamorelin at the "Preclinical" evidence tier — the evidence is largely animal or in-vitro, with human data thin or absent. It is catalogued as an engineered analog built on an endogenous hormone, and the tier is an editorial judgment about the public literature that can change as the science does.
What is the half-life of Ipamorelin?: The reported circulating half-life of Ipamorelin is ~2 h.

Selected literature

Curated peer-reviewed reviews, sourced from PubMed. Selected for relevance, not exhaustive — open any entry on PubMed for the full record and its primary citations.

1.Ipamorelin, the first selective growth hormone secretagogue · European journal of endocrinology, 1998 · PMID 9849822
2.Ipamorelin, a new growth-hormone-releasing peptide, induces longitudinal bone growth in rats · Growth hormone & IGF research, 1999 · PMID 10373343
3.Safety and Efficacy of Approved and Unapproved Peptide Therapies for Musculoskeletal Injuries and Athletic Performance · Sports medicine (Auckland, N.Z.), 2026 · PMID 41966639

External references

Ipamorelin in the public knowledge graph — the same entity resolved across the authoritative chemistry and protein databases.