Summary

Ipamorelin is a synthetic pentapeptide growth hormone secretagogue (GHS) that stimulates growth hormone (GH) release via the ghrelin receptor (GHS-R1a). It is valued in research for its relative selectivity — minimal effect on cortisol and prolactin — compared to earlier GHRPs. Evidence is primarily from preclinical studies, with limited human clinical data.

Mechanism

Ipamorelin acts as an agonist at the growth hormone secretagogue receptor (GHS-R1a), the same receptor targeted by ghrelin. Binding to GHS-R1a on somatotroph cells in the anterior pituitary stimulates the release of growth hormone in a pulsatile manner. Unlike GHRH (which acts through a separate GHRH receptor), ipamorelin's action is mediated through the ghrelin pathway. Its selectivity profile — minimal ACTH, cortisol, and prolactin stimulation — distinguishes it from earlier GHRPs like GHRP-2 and GHRP-6, which can increase these hormones at higher doses.

Evidence base

Evidence Grading: Limited

The evidence base for ipamorelin consists primarily of preclinical studies and early-phase human pharmacology trials. No Phase III data exists.

Key studies:

  • Raun K, et al. (1998) — original pharmacological characterisation in rats; demonstrated GH release with minimal ACTH/cortisol effects
  • Phase I human pharmacokinetics showing dose-dependent GH release after SC administration
  • A Phase II study in hip fracture recovery (limited published results)

Limitations: No large-scale clinical trials. Much of the current interest is from non-clinical sources. The compound was not advanced to late-stage development by Novo Nordisk.

Protocols

In published pharmacology studies, ipamorelin was administered subcutaneously at 0.06–1.0 µg/kg. Research discussions reference pulsatile dosing to mimic physiological GH patterns. No chronic dosing protocol is validated in clinical literature. All use is research-only.

Ipamorelin is not a licensed medicine in the UK and is not controlled under the Misuse of Drugs Act. It is sold as a research chemical. Ipamorelin has no MHRA marketing authorisation and is not approved for human use by any major regulatory body. Researchers should ensure compliance with UK chemicals and workplace safety legislation.

Vendor notes

Ipamorelin is available from several UK research peptide suppliers. Buyers should verify purity via COAs and third-party testing. See the vendor directory for vetted UK suppliers.

References

  1. Raun K, Hansen BS, Johansen NL, Thøgersen H, Madsen K, Ankersen M, Andersen PH. Ipamorelin, the first selective growth hormone secretagogue. European Journal of Endocrinology. 1998;139(5):552–558.
  2. Fuh VL, et al. Dose-dependent stimulation of growth hormone release by ipamorelin, a novel GHRP, in healthy human subjects. Endocrine Society Annual Meeting. 1998.
  3. Bowers CY. GH releasing peptides — structure and kinetics. Journal of Pediatric Endocrinology & Metabolism. 1996;9(3):327–335.
  4. Patchett AA, et al. Design and biological activities of L-163,191 (MK-0677): a potent, orally active growth hormone secretagogue. Proceedings of the National Academy of Sciences. 1995;92(15):7001–7005.