Ipamorelin Peptide

Ipamorelin is a synthetic peptide composed of five amino acids, classifying it as a pentapeptide (Aib-His-D-2-Nal-D-Phe-Lys-NH₂), and is formally recognised as a Growth Hormone Secretagogue (GHS). Its name reflects the purpose behind its development, as it was specifically designed to act through binding to ghrelin receptors. These receptors, located on the pituitary gland—which plays a central role in growth hormone (hGH) production—are also referred to as Growth Hormone Secretagogue receptors (GHS-R).

Through this proposed mechanism, Ipamorelin may interact with GHS-Rs on pituitary cells, potentially stimulating the release of growth hormone. This action aligns with its classification as a growth hormone secretagogue, suggesting a role in influencing endogenous GH secretion via ghrelin receptor activation.

Overview

Ipamorelin is considered one of the first synthetic growth hormone secretagogues (GHS) noted for its high selectivity, with research suggesting it may stimulate the production of human growth hormone (hGH) without significantly affecting other pituitary hormones such as prolactin or adrenocorticotropic hormone (ACTH). This selective activity distinguishes it from less specific GHS compounds.

The increase in hGH associated with Ipamorelin exposure may contribute to enhanced lipolysis and stimulate the production of insulin-like growth factor-1 (IGF-1). IGF-1 is regarded as a key mediator of the anabolic effects of growth hormone, potentially supporting cellular proliferation as well as bone and muscle development. Through these pathways, Ipamorelin may influence processes related to tissue growth and metabolic function.(1)

Chemical Makeup

  • Molecular Formula: C38H49N9O5

  • Molecular Weight: 711.86 g/mol

  • Other Known Titles: NNC 26-0161

Research and Clinical Studies
Ipamorelin Peptide and Selective Agonism

Based on a 1998 study conducted in murine models, researchers suggested that Ipamorelin may stimulate the release of growth hormone from pituitary cells. When administered to swine and pentobarbitone-anesthetised rats, the peptide was reported to induce an increase in growth hormone secretion. Further observations led researchers to propose that, similar to other growth hormone-stimulating peptides, Ipamorelin may act as a receptor agonist, promoting GH release through its interaction with growth hormone secretagogue receptors.

Notably, the researchers described Ipamorelin as “the first GHS-R agonist with a selectivity for GH release similar to that displayed by GHRH,” highlighting its specificity as a distinguishing feature and suggesting potential for future clinical investigation.(1) Additional research has supported these findings, indicating that Ipamorelin may increase human growth hormone (hGH) secretion while having minimal impact on other pituitary hormones such as prolactin and adrenocorticotropic hormone (ACTH).(2)

Ipamorelin Peptide and Growth Hormone Synthesis

In vitro studies suggest that Ipamorelin’s interaction with growth hormone secretagogue receptors (GHS-Rs) may influence somatotroph cells in the anterior pituitary by initiating a cascade of intracellular signalling events.(3) This proposed mechanism involves activation of phospholipase C (PLC), which may increase the production of secondary messengers such as inositol triphosphate (IP3) and diacylglycerol (DAG). IP3 is thought to stimulate the release of calcium ions (Ca²⁺) from intracellular stores, while DAG may activate protein kinase C (PKC). The resulting rise in intracellular calcium levels, along with PKC activation, is believed to promote the exocytosis of growth hormone-containing vesicles from pituitary cells.(3)

In a clinical trial conducted in late 1999, eight subjects were administered Ipamorelin at regular 15-minute intervals over a defined period. Approximately two hours after administration, researchers reported an apparent increase in growth hormone levels. Specifically, GH concentrations were observed to rise to as much as 80 mIU/L (approximately 26.6 ng/mL). When compared to placebo baseline levels of around 1.31 mIU/L (0.4 ng/mL), this represented an increase of more than 60-fold, suggesting a substantial stimulatory effect on growth hormone secretion under the study conditions.(4)

Ipamorelin Peptide and Bone Tissue

It has been proposed that Ipamorelin may influence bone mineral density through mechanisms linked to growth hormone activity. The theory suggests that Ipamorelin could stimulate osteoblasts—cells responsible for bone formation—via hGH-mediated pathways, potentially enhancing their proliferation, growth, and differentiation.

In one study,(5) murine models were administered either Ipamorelin or a placebo, and the effects on bone mineral density were assessed using dual-energy X-ray absorptiometry (DEXA) at key skeletal sites, including the femur and the L6 vertebra. Following the study period, additional analysis was performed using peripheral quantitative computed tomography (pQCT) to examine bone structure in greater detail. The findings suggested that Ipamorelin exposure may have been associated with increased body mass and elevated bone mineral content (BMC) in both tibial and vertebral regions compared to the control group.

Further pQCT analysis indicated that the increase in cortical BMC may have been related to an expansion in the bone’s cross-sectional area, rather than a change in density. This was supported by observations that cortical volumetric bone mineral density (BMD)—the ratio of BMC to bone area—remained relatively unchanged. These results suggest that the peptide may contribute to increases in bone size or volume, particularly in the femur and L6 vertebra, rather than altering bone density itself.(5)

Ipamorelin Peptide and Digestion

Researchers have investigated the potential effects of Ipamorelin on gastric function, particularly its possible role in accelerating gastric emptying. In one study,(6) gastric emptying rates were assessed by measuring the proportion of a marked substance remaining in the stomach 15 minutes after administration via intragastric gavage. The experimental design included surgical intervention in murine models to deliberately slow gastric emptying, which was most evident in the control group. In contrast, models treated with Ipamorelin appeared to exhibit a significantly faster rate of gastric emptying, leading researchers to propose that the peptide may enhance this process.

Further investigation explored the potential influence of Ipamorelin on the contractile activity of gastric smooth muscle. These experiments evaluated muscle responses to stimuli such as acetylcholine and electrical field stimulation. Findings suggested that the reduced peristaltic activity observed in the experimental models was mitigated when Ipamorelin was administered, particularly in combination with ghrelin. This led to the hypothesis that Ipamorelin may enhance the contractility of gastric smooth muscle, thereby supporting improved gastrointestinal motility.(6)

Ipamorelin Peptide and Appetite

The interaction of Ipamorelin with ghrelin receptors has been proposed to influence appetite regulation, potentially leading to increased hunger signals and subsequent changes in body mass. Research observations suggest that experimental models exposed to Ipamorelin demonstrated an approximate 15% increase in body weight.(7) This increase was hypothesised to be associated with proportional enlargement of fat depots relative to total body weight, which may be reflected as a rise in body fat percentage on DEXA assessments.

Additionally, researchers have speculated that Ipamorelin may elevate serum leptin levels—a hormone involved in regulating energy balance and appetite. These findings have led to the suggestion that increased food intake may contribute to the observed weight gain in models exposed to the peptide. It has been proposed that growth hormone secretagogues may influence body fat through mechanisms that are not solely dependent on growth hormone, potentially including enhanced feeding behaviour.(7)

Ipamorelin Peptide and Nitrogen Balance

Researchers have suggested that Ipamorelin may exert anabolic effects, potentially linked to its influence on human growth hormone (hGH) and insulin-like growth factor-1 (IGF-1) synthesis. One way this effect has been explored is through its impact on nitrogen balance, a key indicator of anabolic versus catabolic states within the body. In a specific investigation,(8) the effects of Ipamorelin on liver markers associated with alpha-amino-nitrogen metabolism were examined under experimentally induced catabolic conditions.

The study focused on the liver’s capacity to synthesise urea nitrogen (CUNS), which serves as an indicator of nitrogen processing efficiency. Researchers analysed messenger RNA (mRNA) expression of enzymes involved in the urea cycle, alongside overall nitrogen balance and its distribution across different organs. The findings suggested that Ipamorelin exposure may have resulted in an approximate 20% reduction in CUNS compared to the catabolic condition alone. Additionally, the peptide appeared to reduce the expression of urea cycle enzymes, which may indicate a shift toward improved nitrogen retention.

These observations suggest that Ipamorelin may contribute to restoring nitrogen balance under catabolic stress and potentially enhance nitrogen availability across tissues, supporting its proposed role in anabolic processes.(8)

Ipamorelin peptide is available for research and laboratory purposes only. Please speak to our friendly research team to find out more and for sourcing options.

References:

  1. K. Raun et al., Ipamorelin, the first selective growth hormone secretagogue, Endocrinology, November 1998.

  2. Sinha DK, Balasubramanian A, Tatem AJ, Rivera-Mirabal J, Yu J, Kovac J, Pastuszak AW, Lipshultz LI. Beyond the androgen receptor: the role of growth hormone secretagogues in the modern management of body composition in hypogonadal males. Transl Androl Urol. 2020 Mar;9(Suppl 2):S149-S159. doi: 10.21037/tau.2019.11.30. PMID: 32257855; PMCID: PMC7108996  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7108996/

  3. Jiménez-Reina, L., Cañete, R., de la Torre, M. J., & Bernal, G. (2002). Influence of chronic treatment with the growth hormone secretagogue Ipamorelin, in young female rats: somatotroph response in vitro. Histology and histopathology, 17(3), 707–714.  https://doi.org/10.14670/HH-17.707

  4. Gobburu, J.V.S., Agersø, H., Jusko, W.J. et al. Pharmacokinetic-Pharmacodynamic Modeling of Ipamorelin, a Growth Hormone Releasing Peptide, in Human Volunteers. Pharm Res 16, 1412–1416 (1999).

  5. Svensson, J., Lall, S., Dickson, S. L., Bengtsson, B. A., Rømer, J., Ahnfelt-Rønne, I., Ohlsson, C., & Jansson, J. O. (2000). The GH secretagogues ipamorelin and GH-releasing peptide-6 increase bone mineral content in adult female rats. The Journal of endocrinology, 165(3), 569–577.  https://doi.org/10.1677/joe.0.1650569

  6. Greenwood-Van Meerveld, B., Tyler, K., Mohammadi, E., & Pietra, C. (2012). Efficacy of ipamorelin, a ghrelin mimetic, on gastric dysmotility in a rodent model of postoperative ileus. Journal of experimental pharmacology, 4, 149–155.  https://doi.org/10.2147/JEP.S35396

  7. Lall, S., Tung, L. Y., Ohlsson, C., Jansson, J. O., & Dickson, S. L. (2001). Growth hormone (GH)-independent stimulation of adiposity by GH secretagogues. Biochemical and biophysical research communications, 280(1), 132–138.   https://doi.org/10.1006/bbrc.2000.4065

  8. Aagaard, N. K., Grøfte, T., Greisen, J., Malmlöf, K., Johansen, P. B., Grønbaek, H., Ørskov, H., Tygstrup, N., & Vilstrup, H. (2009). Growth hormone and growth hormone secretagogue effects on nitrogen balance and urea synthesis in steroid treated rats. Growth hormone & IGF research: official journal of the Growth Hormone Research Society and the International IGF Research Society, 19(5), 426–431.   https://doi.org/10.1016/j.ghir.2009.01.001

Dr. Marinov

Dr. Marinov (MD, Ph.D.) is a researcher and chief assistant professor in Preventative Medicine & Public Health. Prior to his professorship, Dr. Marinov practiced preventative, evidence-based medicine with an emphasis on Nutrition and Dietetics. He is widely published in international peer-reviewed scientific journals and specializes in peptide therapy research.

Ipamorelin Peptide