Ipamorelin 5mg

Ipamorelin (Aib-His-D-2-Nal-D-Phe-Lys-NH₂) is a synthetic pentapeptide that binds the growth hormone secretagogue receptor type 1a (GHS-R1a) with an EC₅₀ of approximately 1.3 nM in cell-based cAMP assays. First characterized by Raun et al. (1998), it is classified as a selective GHS-R1a agonist.

Molecular Profile

GHS-R1a is a Gαq/11-coupled GPCR expressed primarily in the anterior pituitary and hypothalamic arcuate nucleus. Ipamorelin binding activates phospholipase C → IP₃/DAG → intracellular Ca²⁺ release, triggering GH vesicle exocytosis from somatotroph cells. Unlike hexarelin and GHRP-6, ipamorelin does not significantly activate GHS-R1a-independent pathways at the adrenal cortex — in vivo data shows no statistically significant elevation of ACTH, cortisol, prolactin, FSH, LH, or TSH at GH-releasing concentrations (Raun et al., 1998).

Published Data

Dose-response characterization in Sprague-Dawley rats established GH-releasing potency comparable to GHRP-6 with a selectivity index >100-fold for GH over cortisol (Raun et al., Eur J Endocrinol 1998). Subsequent studies examined ipamorelin in the context of gastrointestinal smooth muscle signaling, specifically its effects on GHS-R1a-expressing enteric neurons and circular muscle contractility in rodent ileus models (Greenwood-Van Meerveld et al., JPET 2012). The compound has also been used as a reference agonist in GHS-R1a binding displacement assays across multiple published pharmacological studies.

Research Relevance

Ipamorelin's high selectivity index for somatotroph GHS-R1a over adrenal and gonadotroph pathways makes it a standard reference compound for controlled studies of isolated GH-axis signaling without confounding multi-hormone activation.