Ipamorelin: What It Is and How It Is Studied

Ipamorelin is a synthetic pentapeptide that acts as a growth hormone (GH) secretagogue by binding selectively to the GHS-R1a receptor. Its sequence is Aib-His-D-2-Nal-D-Phe-Lys-NH2; two non-natural residues — α-aminoisobutyric acid at position one and D-2-naphthylalanine at position three — confer resistance to enzymatic degradation. The property most consistently noted in the published literature is selectivity: at concentrations that produce GH release, cortisol and prolactin levels do not rise significantly. PeptoClinic supplies ipamorelin as research material to Argentina and other destinations in the region.

The GHS-R1a receptor

The GHS-R1a (Growth Hormone Secretagogue Receptor, subtype 1a) is a G-protein-coupled receptor expressed primarily in the anterior pituitary and hypothalamus. Ghrelin is its endogenous ligand. Ipamorelin acts as a synthetic agonist at that same receptor: when it binds to somatotropic cells in the anterior pituitary, it activates the signalling cascade that culminates in pulsatile GH release.

This pathway is distinct from that of GHRH analogues such as sermorelin or CJC-1295 without DAC, which act on the GHRH receptor (GHRHR). In experimental designs, combining a GHS-R1a agonist with a GHRHR agonist produces greater GH release than either compound alone, because the two pathways are additive. That additivity has methodological value when an experiment needs to modulate the magnitude of GH secretion in a controlled way.

The central finding: selectivity

The reference study is Raun K et al., published in the *European Journal of Endocrinology* in 1998 (PMID 9849822). Its title states the finding directly: *Ipamorelin, the first selective growth hormone secretagogue*.

The experiment measured GH, cortisol, ACTH and prolactin in rats and pigs following administration of ipamorelin, GHRP-6 and GHRP-2. All three compounds produced GH release. The difference lay in the secondary hormones: GHRP-6 and GHRP-2 raised cortisol and ACTH at comparable concentrations; ipamorelin did not. The authors concluded that ipamorelin is the first GH secretagogue with high selectivity for the GH axis without significantly activating the corticotropic axis.

That finding is what defines ipamorelin as a compound of research interest in studies of GH regulation. It allows investigation of GH secretion without changes in cortisol introducing noise into the experimental result.

Published research models

Johansen PB et al. studied the effect of ipamorelin on longitudinal bone growth in rats, published in 1999 in *Growth Hormone and IGF Research* (PMID 10373342). The design measured tibial bone length in treated and control animals. The article is available on PubMed.

The PubMed database lists additional publications investigating ipamorelin in models of sarcopenia, post-surgical muscle recovery and sleep regulation. That literature is accessible by searching "ipamorelin" at pubmed.ncbi.nlm.nih.gov and filtering by study type.

As of August 2026, ipamorelin holds no approval as a medicine from any regulatory authority. There are no completed phase III clinical trials with ipamorelin as a standalone product. Its regulatory status in the United States, the European Union and Argentina is the same: research material without an approved therapeutic indication.

Ipamorelin versus other GH secretagogues

The PeptoClinic catalogue includes compounds that stimulate GH through distinct pathways, and those differences matter for experimental design.

Via the GHRHR pathway: sermorelin and tesamorelin are GHRH analogues. They act on the pituitary receptor for growth hormone-releasing hormone. Sermorelin has a short half-life; tesamorelin carries structural modifications that improve its stability in solution.

Via the GHS-R1a pathway: ipamorelin, GHRP-6 and GHRP-2 act on the GH secretagogue receptor. The distinction among them is the selectivity described above: GHRP-6 and GHRP-2 activate the corticotropic axis; ipamorelin does not do so at the concentrations documented in the published models.

If an experiment requires stimulating GH without confounding the result with cortisol changes, the published literature identifies ipamorelin as the compound with that profile. If a design calls for combining both pathways, the most common pairing in published studies is ipamorelin with a GHRH analogue — because the two mechanisms are additive, not redundant.

For laboratory research only

PeptoClinic supplies ipamorelin exclusively as Research Use Only (RUO) material, intended for in vitro and laboratory model research.

• Ipamorelin is not a medicine and not a supplement.
• It carries no therapeutic indication evaluated by the FDA, ANMAT or any equivalent authority.
• PeptoClinic is not a clinic, a pharmacy or a source of guidance on human use.
• Requests for administration protocols in humans are declined.

This framing is not generic legal text. It describes the type of operation PeptoClinic runs and the type of customer it can serve.

Documentation and quoting

Every lot of ipamorelin that PeptoClinic dispatches ships with a verifiable certificate of analysis from an independent laboratory. The certificate specifies the compound, the analytical method — HPLC — and the numeric purity result for that specific lot. The catalogue standard is ≥99% by HPLC.

If a research programme requires additional specifications — endotoxin testing, nominal concentration, a specific vial format — the technical team reviews those requirements as part of the consultation. A quote is requested through the catalogue page by describing the compound, the specification and the quantity. A written response arrives within the next business day.

Shipments to Argentina are prepared with documentation as laboratory reference material for customs. PeptoClinic details how that documentation is handled for each destination on its shipping page.