Overview

Ipamorelin is a synthetic pentapeptide developed in the late 1990s by Novo Nordisk as a growth-hormone secretagogue. It acts at the ghrelin receptor (GHS-R1a) on the anterior pituitary and hypothalamus, triggering release of growth hormone from somatotroph cells.

Its most-cited feature in the research literature is selectivity: preclinical work and early clinical studies report that ipamorelin produces GH release comparable to other GHS peptides but with minimal effect on adrenocorticotropic hormone (ACTH), cortisol, or prolactin — a profile distinct from earlier compounds like GHRP-6 and GHRP-2 (Raun et al., 1998).

Mechanism (as reported)

  • GHS-R1a agonism. Ipamorelin binds the ghrelin/growth-hormone secretagogue receptor 1a, activating a distinct signalling pathway from GHRH.
  • Preserved GH pulsatility. Studies indicate ipamorelin amplifies pulsatile GH release without abolishing the endogenous rhythm.
  • Synergy with GHRH analogues. The combination of a GHRH analogue (e.g., CJC-1295 with DAC or sermorelin) and ipamorelin produces a greater GH release than either alone, because the two peptides engage distinct receptor systems and their signalling is complementary.

Research findings

  • Raun et al. (1998) reported that ipamorelin selectively released growth hormone in swine and rat models with no significant effect on ACTH, cortisol, or prolactin — the primary rationale for its early development.
  • Andersen et al. (2001) reported dose-dependent GH release in healthy adult subjects.
  • A Phase II trial (Beck et al., 2014) evaluated ipamorelin for postoperative ileus and reported acceleration of gastrointestinal transit, consistent with the ghrelin-agonist mechanism.

Common dosing (animal studies and Phase I data)

Reported research doses commonly fall between 200 and 300 mcg per administration. Because the half-life is short (~2 hours), literature and research writeups typically describe 1–3 daily doses, most often at bedtime or immediately before/after training in exercise-physiology contexts. Timing away from meals is commonly discussed because circulating fatty acids and glucose can blunt the GH response.

Reconstitution

A common reconstitution reported in the literature is 5 mg of peptide in 2 mL bacteriostatic water, producing a 2,500 mcg/mL solution. A 250 mcg research dose corresponds to 0.1 mL, or 10 units on a U-100 insulin syringe.

Storage

Lyophilised ipamorelin is generally reported as stable at room temperature for shipping. Once reconstituted, the peptide is typically stored refrigerated at 2–8 °C for up to 4 weeks; longer storage is done frozen.

Common stacks

  • GH Pulse Stack — paired with CJC-1295 DAC as the reference GH-secretagogue combination.
  • Sleep Research Stack — mechanistic complement to a nighttime sermorelin pulse in some reported protocols.

References

  • Raun, K., et al. (1998). “Ipamorelin, the first selective growth hormone secretagogue.” European Journal of Endocrinology, 139(5). PMID 9849830.
  • Andersen, N. B., et al. (2001). “Growth-hormone secretagogues: potential clinical applications.” Endocrinology & Metabolism Clinics of North America.
  • Beck, D. E., et al. (2014). “The effect of ipamorelin, a novel growth hormone secretagogue, on postoperative ileus.” American Journal of Surgery, 208(1). PMID 24580878.