Ipamorelin

Third-generation growth hormone secretagogue and selective ghrelin receptor agonist designed for clean, pulsatile GH release with minimal off-target endocrine effects.

Evidence: Human + Preclinical Function: GH Axis & Recovery Class: GHSR1a agonist (pentapeptide)

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Research frame & potential applications

Ipamorelin is a pentapeptide ghrelin mimetic developed to selectively trigger growth hormone release by activating GHSR1a while sparing ACTH, cortisol and prolactin. It is used in research to map GH pulsatility, explore recovery, body-composition modulation and GI motility (postoperative ileus) with a cleaner endocrine profile than earlier GHRPs.

Research areas & putative benefits

Where Ipamorelin is used as a cleaner GH secretagogue compared with older GHRPs.

Characterising GH axis responsiveness and pulsatile secretion in healthy volunteers and endocrine disorders.
Exploring recovery, lean-mass support and tissue repair in conjunction with exercise or other interventions.
Studying postoperative ileus and GI motility via ghrelin-pathway stimulation in surgical models.
Benchmarking safety and endocrine selectivity versus GHRP‑2, GHRP‑6 and native ghrelin in comparative designs.

Mechanism stack

How Ipamorelin drives GH release and where it diverges from older secretagogues.

Primary receptor

GHSR1a-selective agonism

Ipamorelin mimics ghrelin at the growth hormone secretagogue receptor type 1a on pituitary somatotrophs and hypothalamic neurons, initiating Gq/11-mediated PLC–IP3–DAG signalling and calcium mobilisation for GH release.

Endocrine profile

Minimal ACTH/cortisol impact

Unlike some earlier GHRPs, Ipamorelin shows high selectivity for GH release with little stimulation of ACTH, cortisol or prolactin, giving a cleaner, GH-focused endocrine footprint in trials.

GH physiology

Physiologic-like pulses

Electrophysiological work suggests Ipamorelin induces calcium oscillations and membrane depolarisation patterns in somatotrophs that resemble natural GHRH-driven GH pulses rather than non-physiological dumps.

Peripheral actions

GI motility & appetite

Acting on ghrelin-pathway targets beyond the pituitary, Ipamorelin has been investigated for appetite and bowel-motility modulation, including proof-of-concept work in postoperative ileus models.

Evidence snapshot

Representative findings from GH-release testing and clinical experimentation.

Model / context	Observation	Notes
Rat pituitary & in vivo models Preclinical GH	Ipamorelin releases GH with potency and efficacy comparable to GHRP‑6 while showing high receptor selectivity and a favourable endocrine side-profile.	Helped establish Ipamorelin as a third-generation, more targeted GHRP class member.
Human GH stimulation tests Clinical GH	Acute Ipamorelin dosing produces strong, short-lived GH peaks with minimal changes in ACTH, cortisol or prolactin across several small trials.	Positions Ipamorelin as a useful probe for GH reserve and selective axis stimulation.
Postoperative ileus trials GI motility	A ghrelin mimetic ipamorelin regimen improved GI transit parameters in patients after abdominal surgery in proof-of-concept settings.	Highlights potential beyond musculoskeletal and body-composition research.
Comparative endocrine profiling Selectivity	Across models, Ipamorelin shows less stimulation of cortisol and prolactin than GHRP‑2 and GHRP‑6 at GH-effective doses.	Supports its reputation as a “cleaner” GH secretagogue for research protocols.

Risk frame & unknowns

Considerations when using Ipamorelin as a research tool.

Important research caveats

Long-term GH-axis stimulation may alter glucose tolerance, lipids, fluid balance and cardiac structure, even with selective secretagogues.
Data on chronic, high-frequency Ipamorelin exposure remain limited compared with acute GH testing paradigms.
Co-administration with other GH- or IGF‑1–active agents can create complex interaction patterns not yet fully mapped.
Off-label or unsupervised use carries endocrine, metabolic and oncogenic risks typical of sustained GH/IGF-axis activation.

This dossier summarizes mechanistic, preclinical and clinical findings on Ipamorelin for scientific and educational purposes only. It does not provide medical advice, treatment guidance or dosing recommendations.