Selective stimulation of growth hormone through Ipamorelin – the first selective GH secretagogue

Source: Raun K. et al., European Journal of Endocrinology , 1998, Ipamorelin: The First Selective Growth Hormone Secretagogue


Purpose of the study

To determine the pharmacological profile of Ipamorelin – the first selective Growth Hormone Secretagogue (GHS) – and to evaluate its ability to stimulate growth hormone (GH) secretion without affecting other pituitary hormones such as ACTH, cortisol and prolactin.

Ipamorelin is a synthetic pentapeptide developed as a selective agonist of the GHS-R1a receptor , designed to provide more specific and safer GH stimulation compared to older GHRP peptides (such as GHRP-2 and GHRP-6), which often induce non-specific hormonal responses.


Study design

  • Type: preclinical and clinical experimental studies

  • Models: animal models (rats, pigs) and healthy volunteers

  • Interventions: administration of Ipamorelin in different doses

  • Comparative agents: GHRP-6 and GHRP-2

  • Measured parameters:

    • Serum growth hormone (GH) levels

    • Levels of ACTH, cortisol, prolactin, and other hormones

    • Duration and intensity of hormonal response


Main results

Selectivity of action

  • Ipamorelin causes a dose-dependent and selective increase in GH, without changes in ACTH, cortisol, and prolactin levels.

  • Its profile differs from that of GHRP-6 and GHRP-2, which also activate other hormonal pathways.

Pharmacodynamics

  • A rapid peak of GH is observed about 10 minutes after administration, with a short duration of action (30–60 minutes).

  • The effect is repeatable and stable with consecutive applications, with no signs of desensitization.

Comparative efficiency

  • Ipamorelin shows similar efficacy to GHRP-6 in terms of GH release, but with significantly better selectivity and safety.

Safety

  • No adverse effects on the adrenal axis or other endocrine systems were observed.

  • Good tolerance in animal and human models.


Conclusions

  • Ipamorelin is the first selective GHS-R1a agonist that stimulates only growth hormone without any effect on other pituitary hormones.

  • It shows a dose-dependent, predictable and safe hormonal response .

  • Suitable for studies of GH regulation, anabolic processes and models of GH deficiency.


Restrictions

  • The main data are from early preclinical and phase I studies.

  • Long-term clinical results are not available.


Practical importance

  • Ipamorelin is a promising selective GH secretagogue with an excellent safety profile.

  • Suitable for research applications in endocrinology and metabolic sciences.

  • Advantage over classic GHRP peptides due to the lack of effect on ACTH and cortisol.