Ipamorelin
A synthetic pentapeptide and selective ghrelin/GHS-R1a agonist studied as a growth hormone secretagogue in laboratory models.
Overview
Ipamorelin is a synthetic pentapeptide originally developed at Novo Nordisk under the development code NNC 26-0161 and first described in the late 1990s. Structurally derived from the growth-hormone-releasing peptide GHRP-1, it belongs to the class of growth hormone secretagogues (GHS), compounds that act on the ghrelin receptor (GHS-R1a) rather than on the growth-hormone- releasing hormone (GHRH) receptor. In its foundational characterisation it was reported as the first selective growth hormone secretagogue (Raun et al., 1998).
The feature most consistently emphasised in the literature is its selectivity. In the original animal and in-vitro work, Ipamorelin released growth hormone with potency and efficacy comparable to earlier secretagogues, yet did not raise adrenocorticotropic hormone (ACTH) or cortisol to levels meaningfully different from those seen after GHRH stimulation, and was reported not to affect prolactin, FSH, LH, or TSH (Raun et al., 1998). It is studied in the research setting as a selective probe of the ghrelin/GHS-R1a axis and as a reference GH-secretagogue. It sits alongside related secretagogues such as CJC-1295 and Ipamorelin in the wider GH-secretagogue research cluster.
Molecular Profile
The sequence incorporates two non-proteinogenic residues, aminoisobutyric acid (Aib) and D-2-naphthylalanine (D-2-Nal), together with a D-phenylalanine and a C-terminal amide. These non-standard residues are understood to contribute to receptor selectivity and to resistance against enzymatic breakdown relative to all-L-amino-acid peptides.
Mechanism of Action
Findings below are drawn from published in-vitro and animal-model research:
- Ghrelin/GHS-R1a agonism: Ipamorelin is reported to act as an agonist at the growth hormone secretagogue receptor type 1a (GHS-R1a), the same receptor targeted by the endogenous peptide ghrelin, stimulating growth hormone release through a pathway distinct from the GHRH receptor (Raun et al., 1998).
- Selective growth hormone release: In rat pituitary cell and in-vivo studies, Ipamorelin released growth hormone in a dose-dependent manner without significantly elevating ACTH, cortisol, prolactin, FSH, LH, or TSH, a selectivity profile reported to distinguish it from earlier secretagogues such as GHRP-6 and pralmorelin (Raun et al., 1998).
- Skeletal endpoints in rodent models: Continuous administration in adult female rats has been reported to increase bone mineral content as measured by DXA, an effect attributed to sustained activation of the GH/IGF-I axis (Svensson et al., 2000).
- Bone-formation effects under glucocorticoid load: In a glucocorticoid-treated rat model, Ipamorelin was reported to counteract the glucocorticoid-induced reduction in periosteal bone formation rate, framed in the literature as GH-secretagogue modulation of bone turnover (Andersen et al., 2001).
Key Published Research
Ipamorelin, the first selective growth hormone secretagogue
Raun K, et al. European Journal of Endocrinology. 1998; 139(5):552-561 (PMID 9849822)
Foundational pharmacology paper characterising Ipamorelin as a pentapeptide growth hormone secretagogue with high GH-releasing potency and a selectivity profile that spared ACTH and cortisol in research models.
The GH secretagogues ipamorelin and GH-releasing peptide-6 increase bone mineral content in adult female rats
Svensson J, et al. Journal of Endocrinology. 2000; 165(3):569-577 (PMID 10828840)
Reports that continuous administration of ipamorelin increased bone mineral content in adult female rats over a 12-week DXA study, linking the secretagogue to the GH/IGF-I axis.
The growth hormone secretagogue ipamorelin counteracts glucocorticoid-induced decrease in bone formation of adult rats
Andersen NB, et al. Growth Hormone & IGF Research. 2001; 11(5):266-272 (PMID 11735244)
Examines ipamorelin in a glucocorticoid-treated rat model and reports a counteracting effect on the reduction in periosteal bone formation rate.
Prospective, randomized, controlled, proof-of-concept study of the ghrelin mimetic ipamorelin for the management of postoperative ileus in bowel resection patients
Beck DE, et al. International Journal of Colorectal Disease. 2014; 29(12):1527-1534 (PMID 25331030)
A later clinical proof-of-concept study describing ipamorelin as a ghrelin-receptor mimetic; development in this indication was not continued, and the paper is referenced here for its mechanistic framing of the ghrelin/GHS-R1a target.
Storage and Handling
Lyophilised (unreconstituted):Store at -20°C for long-term stability. Keep sealed and protected from light and moisture.
Reconstituted:Store at 2-8°C. Use within 30 days. Avoid repeated freeze-thaw cycles.
Recommended solvent: Bacteriostatic water or sterile water for laboratory use.
Frequently Asked Questions
What class of compound is Ipamorelin?
In the published literature it is described as a synthetic pentapeptide growth hormone secretagogue that acts as a selective agonist at the ghrelin receptor (GHS-R1a), distinct from GHRH-receptor agonists such as Sermorelin and Tesamorelin.
Why is Ipamorelin described as “selective”?
Its foundational characterisation reported growth hormone release without a meaningful rise in ACTH, cortisol, prolactin, or the gonadotropins in research models, which is the basis for the “selective” description (Raun et al., 1998).
What is the reported half-life of Ipamorelin?
The literature reports an elimination half-life of roughly two hours. This figure is provided as published pharmacokinetic context for research reference and is not dosing guidance.
What purity and form does ERC supply for research?
Lyophilised powder at ≥98% HPLC purity, intended strictly for in-vitro laboratory research only.
Disclaimer: This information is compiled from published peer-reviewed literature and is provided for educational and research reference purposes only. It does not constitute medical advice. Ipamorelin sold by Enhanced Research Compounds is intended exclusively for in-vitro research and laboratory use. It is not a therapeutic good, is not listed on the ARTG, and is not approved for human or animal consumption.