Ipamorelin is an invented drug name rather than an abbreviation or numbered fragment.

It belongs to a family known as growth-hormone secretagogues, or more specifically GHRPs (growth-hormone-releasing peptides). Unlike GHRH-type molecules, which mimic the hypothalamic releasing hormone, ipamorelin works through a different receptor — the one that normally responds to ghrelin, the so-called “hunger hormone” that also stimulates growth-hormone release.

It is a very short synthetic peptide — just five amino acids — several of which are non-natural building blocks.

Its established structure is Aib-His-D-2-Nal-D-Phe-Lys-NH2. Several of these residues — the alpha-aminoisobutyric acid (Aib), a D-configured naphthylalanine, and a D-phenylalanine — are not standard natural amino acids. They were deliberately chosen to fit the ghrelin receptor and to resist enzymatic breakdown.

It was developed in the late 1990s by researchers at Novo Nordisk.

Ipamorelin was first described in a 1998 report by Raun and colleagues in the European Journal of Endocrinology, which characterized it as a selective growth-hormone releaser. It emerged from a line of research into synthetic secretagogues that followed earlier peptides such as GHRP-6 and GHRP-2.

The design aim was selectivity: to release growth hormone without stirring up the other hormones that earlier peptides affected.

The first-generation GHRPs did raise growth hormone, but they also tended to increase cortisol and prolactin by activating neighboring pathways. Ipamorelin was engineered to act cleanly on the ghrelin receptor with minimal effect on cortisol and prolactin in preclinical models. That relative selectivity is the central idea behind the molecule and the main way it was distinguished from its predecessors.

It is produced by solid-phase peptide synthesis.

The five residues, including the non-natural ones, are coupled stepwise on a resin (SPPS), the C-terminus is amidated, and the product is cleaved, purified by high-performance liquid chromatography, and confirmed by mass spectrometry. Its short length makes synthesis straightforward, though the unusual building blocks require specific coupling reagents.

The selectivity story is well supported in preclinical work, but the human clinical record points in an unexpected direction.

Animal and cell studies consistently show that ipamorelin releases growth hormone with comparatively little cortisol or prolactin response. However, its only human clinical trials were run for an entirely different purpose: as a treatment for postoperative ileus (the temporary shutdown of gut movement after surgery), taking advantage of the ghrelin receptor’s role in gut motility. Those Phase 2 studies did not meet their goals and the program was discontinued. In other words, ipamorelin was never approved or established as a growth-hormone therapy in people.

This entry exists purely as a research and educational reference. It is not a medicine or supplement, and it contains no dosing or usage guidance.