What is Ipamorelin?

Ipamorelin is a pentapeptide (Aib-His-D-2-Nal-D-Phe-Lys-NH2) that functions as a selective growth hormone secretagogue. The peptide stimulates growth hormone release through the ghrelin receptor (GHS-R1a) without significant stimulation of cortisol, prolactin, or other pituitary hormones.

The peptide was developed as a more selective alternative to earlier GH secretagogues (GHRP-2, GHRP-6) that produced broader pituitary hormone responses. Ipamorelin's selectivity for GH release makes it a valuable tool for research into isolated GH axis manipulation.

For UK research laboratories, ipamorelin serves as a reference compound for studies examining selective GH secretion, ghrelin receptor pharmacology, and the metabolic effects of isolated GH stimulation.

Ipamorelin operates through the following mechanism in research models:

Ghrelin Receptor Activation — Ipamorelin binds to the ghrelin receptor (GHS-R1a), a Gq-coupled GPCR expressed in the pituitary, hypothalamus, and peripheral tissues. Receptor activation increases intracellular calcium and phospholipase C activity, leading to growth hormone secretion from somatotroph cells.

Selective GH Secretion — Unlike earlier GH secretagogues (GHRP-2, GHRP-6), ipamorelin stimulates GH release without significant increases in cortisol, prolactin, or ACTH. This selectivity is attributed to differential intracellular signalling or receptor conformation stabilisation that favours GH-specific pathways.

Metabolic Signalling — Through the ghrelin receptor, ipamorelin influences metabolic pathways beyond GH secretion. In cellular models, the peptide affects appetite-regulating circuits, glucose metabolism, and lipid handling.

GH-IGF-1 Axis — The primary physiological effect of ipamorelin is stimulation of the GH-IGF-1 axis. In research models, this leads to increased IGF-1 production, with downstream effects on protein synthesis, lipolysis, and cellular growth.

Ipamorelin is employed across multiple research domains in UK laboratories:

Selective GH Secretion Studies — In vitro studies examine ipamorelin's selectivity for GH secretion compared to other pituitary hormones. Researchers use the peptide to model isolated GH axis stimulation.

Ghrelin Receptor Pharmacology — Ipamorelin serves as a tool compound for studying GHS-R1a receptor biology, biased agonism, and intracellular signalling.

Metabolic Research — Cellular models examine ipamorelin's effects on metabolism, including glucose handling, lipid oxidation, and energy expenditure.

Comparative Secretagogue Studies — Ipamorelin is compared to GHRP-2, GHRP-6, and other secretagogues in cellular and animal studies.

Body Composition Research — In cellular and animal models, ipamorelin is studied in the context of fat metabolism, lean mass preservation, and tissue regeneration.

Ipamorelin is supplied as a lyophilised powder. Standard laboratory preparation:

• Bacteriostatic water (0.9% benzyl alcohol) recommended for reconstitution
• Typical concentrations: 1–10 mg/mL depending on assay requirements
• Solubility: The peptide is generally soluble in aqueous solutions; brief vortexing may aid dissolution
• Protease sensitivity: The D-amino acid substitutions confer some protease resistance, but standard protease inhibitors may be included in incubation media
• pH: Maintain solutions at pH 6.5–7.5

• Lyophilised powder: −20°C, protected from light
• Reconstituted solution: 2–8°C, protected from light
• Stability: 7–14 days under refrigeration; aliquot and freeze at −20°C for extended studies
• Avoid: Repeated freeze-thaw cycles