Ipamorelin

What Is Ipamorelin?

Ipamorelin is a synthetic pentapeptide growth-hormone secretagogue (a GHRP-class ghrelin/GHS-receptor agonist) that stimulates pulsatile GH release from the pituitary. Its sequence is Aib-His-D-2-Nal-D-Phe-Lys-NH2. It is best known as the “selective” GHRP — in preclinical work it released GH with potency comparable to earlier peptides but without meaningfully raising ACTH, cortisol or prolactin. It is sold as a research chemical and used off-label in body-composition and “anti-ageing” peptide stacks, but it is not an approved medicine or dietary supplement, and human efficacy data are limited.

Evidence

The foundational pharmacology comes from Raun et al., who characterised ipamorelin as the first GHRP-receptor agonist with GH-release selectivity resembling GHRH — releasing GH from rat pituitary cells and in vivo without significantly elevating ACTH or cortisol above GHRH-stimulated levels ^{1Reference 1Raun K et al. · 1998In vitroIpamorelin, the first selective growth hormone secretagogue — in vitro / in vivoView study →}. A companion pharmacokinetic study evaluated its absorption, including nasal delivery, and reported markedly lower plasma clearance than GHRP-6 ^{2Reference 2Johansen PB et al. · 1998Pharmacokinetic evaluation of ipamorelin and other peptidyl growth hormone secretagogues with emphasis on nasal absorption — animal PK. https://pubmed.ncbi.nlm.nih.gov/9879640/View study →}. These are animal/in-vitro and PK data; I did not find controlled human clinical-outcome trials (e.g. on muscle mass, fat loss or ageing endpoints) in this quick pass, so claims of those benefits in humans should be treated as uncited.

Dosage & Safety

Ipamorelin is a research peptide — it is not approved as a dietary supplement or as a drug for human therapeutic use, and this entry is informational only. Because the human evidence base is preclinical/PK rather than clinical-outcome, no validated human dose is established, and none is given here (any figures circulating online are not a personal recommendation). As a GH secretagogue it would be expected to raise IGF-1 and could affect insulin sensitivity and fluid balance; formal human interaction, contraindication and long-term-safety data are not established / not assessed in this pass. Toxicity is not yet characterised from a citable human basis.

References

1. Raun K, Hansen BS, Johansen NL, et al. (1998). Ipamorelin, the first selective growth hormone secretagogue — in vitro / in vivo. Eur J Endocrinol. https://pubmed.ncbi.nlm.nih.gov/9849822/
2. Johansen PB, et al. (1998). Pharmacokinetic evaluation of ipamorelin and other peptidyl growth hormone secretagogues with emphasis on nasal absorption — animal PK. https://pubmed.ncbi.nlm.nih.gov/9879640/