Ipamorelin

Description

Product Summary – Ipamorelin – GHSR-1a Agonist

Mechanism of Action of Ipramorelin

Selective Agonist of Ghrelin Receptor

Ipamorelin targets the GHS-R1a receptors present in the hypothalamus and pituitary loci to act as a dose-dependent facilitation of GH secretory bursts. “Ipamorelin causes rapid, pulsatile GH secretion when administered systemically due to the receptor’s capacity for peptide recognition and biased signalling, involving constitutive activity and ligand-dependent engagement of G proteins and β-arrestin. [1]

Minimal Effect on Cortisol & Prolactin

Ipamorelin induces a selective release of GH with minimal to no stimulation of ACTH, cortisol, or prolactin, even at doses sufficient to elicit robust GH secretion. In contrast, clinical comparative studies show that earlier GHRPs such as GHRP-6 and GHRP-2 often trigger significant increases in ACTH, cortisol, and prolactin.

The selectivity of ipamorelin is dose and species-dependent due to its receptor engagement, tissue penetration, and off-target receptor interactions. 

Insulin-like Growth Factor-1 (IGF-1) Production

Acute and repeated peptide-induced GH pulses cause the IGF-1 release from the liver. Although the single doses secrete the rapid GH peaks, measurable rises of IGF-1 in serum require sustained and repeated dosing. [3]

Anabolic & Fat-Metabolism Effects

In preclinical and limited clinical contexts, ipamorelin was found to cause increased markers of anabolism and attenuated glucocorticoid-induced catabolism in rodent bones. Ipamorelin also modulates the energy balance by increasing the appetite, promoting adipogenesis, and limiting the lipolysis through the ghrelin receptor activation. [4]

Net body composition effects of ipamorelin are context-dependent. In cachectic or GH-deficient states, anabolic and lean-mass benefits are predominant, while in GH-intact systems, enhanced adiposity and attenuated fat distribution are prevailing. [5]

Tolerability and Safety Considerations of Ipramorelin

• Generally well tolerated in human and animal studies.
• The most common adverse events can be injection site irritation, mild headache, and transient flushing.
• Selective GH secretagogue → minimal effects on cortisol or prolactin compared to earlier GHRPs.
• Long-term safety not fully established; data mostly from short-term trials and research use.

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Citations

• Shiimura, Y., Kojima, M., & Sato, T. (2025). How the ghrelin receptor recognizes the acyl-modified orexigenic hormone. Frontiers in molecular neuroscience, 18, 1549366. https://doi.org/10.3389/fnmol.2025.1549366
• Raun, K., Hansen, B. S., Johansen, N. L., Thøgersen, H., Madsen, K., Ankersen, M., & Andersen, P. H. (1998). Ipamorelin, the first selective growth hormone secretagogue. European journal of endocrinology, 139(5), 552–561. https://doi.org/10.1530/eje.0.1390552
• Howick, K., Griffin, B. T., Cryan, J. F., & Schellekens, H. (2017). From Belly to Brain: Targeting the Ghrelin Receptor in Appetite and Food Intake Regulation. International journal of molecular sciences, 18(2), 273. https://doi.org/10.3390/ijms18020273
• Andersen, N. B., Malmlöf, K., Johansen, P. B., Andreassen, T. T., Ørtoft, G., & Oxlund, H. (2001). The growth hormone secretagogue ipamorelin counteracts the glucocorticoid-induced decrease in bone formation of adult rats. Growth hormone & IGF research: official journal of the Growth Hormone Research Society and the International IGF Research Society, 11(5), 266–272. https://doi.org/10.1054/ghir.2001.0239
• Sinha, D. K., Balasubramanian, A., Tatem, A. J., Rivera-Mirabal, J., Yu, J., Kovac, J., Pastuszak, A. W., & Lipshultz, L. I. (2020). Beyond the androgen receptor: The role of growth hormone secretagogues in the modern management of body composition in hypogonadal males. Translational Andrology and Urology, 9(Suppl 2), S149. https://doi.org/10.21037/tau.2019.11.30