Ipamorelin in Canada: GH-Secretagogue Selectivity, Metabolic Signals, and the Research Landscape

Ipamorelin is a synthetic pentapeptide that acts on the ghrelin receptor, also called the growth hormone secretagogue receptor (GHS-R1a). It was described in 1998 as the first selective growth hormone secretagogue, and it is widely used in the laboratory as a reference agonist for that receptor.

Structure and receptor selectivity

Ipamorelin has the sequence Aib-His-D-2Nal-D-Phe-Lys-NH2. Three features of that sequence set it apart from natural peptides: it contains the non-natural amino acid Aib (aminoisobutyric acid), two D-amino acids (D-2-naphthylalanine and D-phenylalanine), and an amidated C-terminus. These modifications are a common way to make a short peptide more resistant to enzymatic cleavage.

Ipamorelin acts on the ghrelin receptor, which is separate from the receptor for growth hormone-releasing hormone (GHRH). The ghrelin receptor was identified in 1996 by Howard and colleagues (Science), and its natural ligand, ghrelin, was discovered in 1999 by Kojima and colleagues (Nature). Because the two receptors are distinct, compounds acting on each can be used to study the pathways separately or together, which is why Ipamorelin is often studied alongside GHRH analogs such as CJC-1295.

Published preclinical work

The paper most often cited is the original description by Raun and colleagues (European Journal of Endocrinology, 1998). The group characterized Ipamorelin in cultured rat pituitary cells and in animal models, and reported that it stimulated growth hormone release through the ghrelin receptor.

The feature that gave the paper its title is selectivity. In the models the group reported, Ipamorelin had little effect on other pituitary hormones such as ACTH and cortisol, unlike several earlier secretagogues. Almost all of the published work on Ipamorelin is preclinical, using cell culture or animal models. Results in one model do not establish activity in another.

How it compares with GHRP-6 and GHRP-2

GHRP-6 and GHRP-2 are earlier synthetic growth hormone-releasing peptides that also act on the ghrelin receptor. Both are hexapeptides, while Ipamorelin has five amino acids. In the Raun paper, Ipamorelin was compared with these earlier compounds, and the difference highlighted was its narrower hormonal profile in the models used: the earlier peptides also affected ACTH and cortisol, while Ipamorelin did not in the same experiments.

• GHRP-6: a hexapeptide and one of the first synthetic ghrelin receptor agonists, used as a comparison compound in the early literature.
• GHRP-2: a hexapeptide in the same family, also used as a comparison compound.
• Ipamorelin: a pentapeptide, described as the first selective secretagogue because of its narrower profile in the reported models.

Researchers choosing a reference agonist for the ghrelin receptor often weigh this selectivity against the larger body of earlier literature on GHRP-6 and GHRP-2.

Why selectivity matters in experimental design

A reference agonist is most useful when it does one thing. If a compound acts on the receptor being studied but also changes other hormones, it becomes harder to tell which observation comes from which pathway. A narrower profile makes it easier to attribute a measured change to ghrelin receptor signaling. This is the main reason Ipamorelin appears in receptor pharmacology work as a comparison or control compound, rather than any single result reported for it.

It also explains why researchers record exactly which secretagogue was used. Compounds in this family can look similar on paper, but their published profiles differ, and results obtained with one should not be assumed for another.

How it fits with GHRH analogs

Ipamorelin and the GHRH analogs act on different receptors. Our article comparing GHRH analogs sets out how Sermorelin, CJC-1295 and Tesamorelin differ, and our CJC-1295 and Ipamorelin overview explains why the two classes are sometimes studied together. CJC-1295 + Ipamorelin is supplied as a combined research product.

Handling in the laboratory

Ipamorelin is supplied as a lyophilized powder. Storage and handling recommendations for research peptides are set out in our storage and handling guide.

Testing and documentation

Every lot we sell is tested by Freedom Diagnostics, an independent laboratory, using HPLC for purity and mass spectrometry for identity. Our current Ipamorelin lot tested at 99.914% purity by HPLC. We publish results as tested, and the certificate is in our COA library, where it can be verified directly with the lab. See our guide to how to verify a COA.

For research purposes only. All products from Canada Research Labs are supplied strictly as reference materials for in-vitro laboratory research by qualified professionals. They are not drugs, natural health products or cosmetics, and have not been authorized by Health Canada for any human or veterinary use.