Sermorelin and Ipamorelin are synthetic peptides that, as suggested by the reports, are designed to stimulate growth hormone production through distinct yet complementary pathways.
Sermorelin, composed of 29 amino acids(1), appears to act as a functional equivalent to natural growth hormone-releasing hormone (GHRH), albeit in a truncated form known as GRF (1-29). Studies suggest that this peptide targets the GHRH receptors in the pituitary gland, potentially enhancing the secretion of growth hormone.(3)
Fig 1. Sermorelin Chemical Structure
On the other hand, Ipamorelin, comprising 5 amino acids(2), appears to operate via the ghrelin pathway, mimicking the action of the hunger hormone ghrelin to stimulate growth hormone release.(4)
Fig 2. Ipamorelin Chemical Structure
While Sermorelin reportedly acts directly on growth hormone-releasing hormone (GHRH) receptors, Ipamorelin appears to target ghrelin receptors in the anterior pituitary gland, known as Growth Hormone Secretagogues Receptors 1 Alpha (GHS-R1a). Consequently, it is also postulated that Sermorelin may retain the fundamental capability of GHRH, potentially stimulating the intermittent release of growth hormone by engaging GHRH receptors in the pituitary gland. This action is presumed to subsequently elevate levels of insulin-like growth factor-1 (IGF-1), recognized as the primary mediator of the anabolic properties of growth hormone.
In contrast, Ipamorelin does not appear to operate via GHRH receptors but rather functions as a growth hormone secretagogue (GHS), akin to Growth Hormone Releasing Peptides (GHRPs). Ipamorelin is purported to mimic the action of ghrelin, the hunger hormone, by targeting ghrelin receptors (GHS-R1a) in the anterior pituitary gland. This characteristic endows Ipamorelin with high selectivity as a secretagogue, rendering it a potent agonist for the growth hormone/ghrelin secretagogue receptor. Given the distinct modes of action exhibited by these peptides, their concomitant exposure may potentially augment growth hormone response in a synergistic manner.
Notably, a significant disparity between the two peptides lies in their respective half-lives, with Sermorelin exhibiting a shorter half-life of approximately 11 to 12 minutes compared to Ipamorelin’s longer half-life of approximately 2 hours.(5) Consequently, it is conjectured that Sermorelin may evoke an immediate growth hormone response, whereas Ipamorelin may sustain this process over prolonged durations.
Sermorelin and Ipamorelin Growth Hormone-Related Research
Research suggests that Sermorelin and Ipamorelin, both peptides under scrutiny for their prospective roles in augmenting growth hormone levels and modulating insulin-like growth factor-1 (IGF-1), may exhibit noteworthy impacts on growth hormone secretion.
Investigations suggest that Sermorelin exposure in animal research models may elicit an average increase of above 80% in growth hormone levels, sustained for approximately two hours.(6) Additionally, a protracted 16-week study posited a potential rise of up to 107% in growth hormone levels, accompanied by a corresponding increase in IGF-1 levels.(7) Interestingly, the same study(7) also report that “although an increase in skin thickness was found in both genders, increases in lean body mass, insulin sensitivity, general well-being, and libido… These observations suggest that [peptide exposure] induced anabolic effects favoring [male species] more than [females].”
Conversely, Ipamorelin studies indicate a substantial elevation in growth hormone levels. When juxtaposed with placebo, this surge in growth hormone levels equates to a remarkable increase exceeding 6000%.(8) While both peptides exhibit robust potential in elevating growth hormone and IGF-1 levels, variations in the extent and duration of these elevations may exist between the two.
Ipamorelin Research in Bone Mineral Density (BMD)
Ipamorelin research study findings suggest its potential in augmenting bone mineral density, attributed to its purported influence on lean and total weight.
Experimental investigations(9) utilizing mouse models suggest a potential association between Ipamorelin exposure and increased bone mineral content, particularly in regions such as the femur and L6 vertebrae. Real-time dual-energy X-ray absorptiometry (DEXA) scans revealed notable alterations in bone mineral content, with a specific focus on the femur and L6 vertebrae. Preliminary findings indicate a plausible correlation between Ipamorelin exposure and enhanced bone mineral content, as exhibited in DEXA scans and peripheral quantitative computed tomography (pQCT) analyses.
Ipamorelin Research in Gastric Motility
Numerous investigations have scrutinized “Ipamorelin’s ability to improve gastric motility in the setting of postoperative ileus.”(9)
A rodent model study(9) was conducted, inducing post-operative ileus (POI), wherein half of the subjects were exposed to Ipamorelin while the remaining served as the control group. Subsequent analysis revealed a concentration-dependent effect, wherein escalating concentrations of Ipamorelin correlated with improved transit rate and gastric emptying, effectively counteracting the adverse gastric effects induced by POI.
Sermorelin and Ipamorelin Research in Body Mass
Sermorelin and Ipamorelin blend may exert discernible influences on lean mass and body composition. Sermorelin interventions have been reportedly associated with an increase in lean body mass by approximately 2.78 lbs (1.26 kg), without concomitant changes in fat mass. This effect is attributed to the peptide’s proposed capacity to augment growth hormone secretion and subsequently elevate IGF-1 levels, a purported mediator of anabolic actions.(10)
Similarly, Ipamorelin exposure may lead to an increase in lean mass, purportedly mediated by enhanced appetite and subsequent weight gain. Studies suggest that animal models exposed to Ipamorelin exhibited a weight gain of approximately 17%, which may be attributed to the peptide’s possible impact on ghrelin receptors.(11)
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References:
- National Center for Biotechnology Information. “PubChem Compound Summary for CID 16129620, Sermorelin” PubChem, https://pubchem.ncbi.nlm.nih.gov/compound/Sermorelin
- National Center for Biotechnology Information. “PubChem Compound Summary for CID 9831659, Ipamorelin” PubChem, https://pubchem.ncbi.nlm.nih.gov/compound/Ipamorelin
- Clark, R G, and I C Robinson. “Growth induced by pulsatile infusion of an amidated fragment of human growth hormone releasing factor in normal and GHRF-deficient rats.” Nature vol. 314,6008 (1985): 281-3. https://pubmed.ncbi.nlm.nih.gov/2858818/
- Raun K, Hansen BS, Johansen NL, Thøgersen H, Madsen K, Ankersen M, Andersen PH. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol. 1998 Nov;139(5):552-61. https://pubmed.ncbi.nlm.nih.gov/9849822/
- Junichi I. et al, Growth hormone secretagogues: history, mechanism of action, and clinical development, JSCM Rapid Communications Vol. 3 Issue 1, 09 February 2020. https://onlinelibrary.wiley.com/doi/full/10.1002/rco2.9
- Vittone, J., Blackman, M. R., Busby-Whitehead, J., Tsiao, C., Stewart, K. J., Tobin, J., Stevens, T., Bellantoni, M. F., Rogers, M. A., Baumann, G., Roth, J., Harman, S. M., & Spencer, R. G. (1997). Effects of single nightly injections of growth hormone-releasing hormone (GHRH 1-29) in healthy elderly men. Metabolism: clinical and experimental, 46(1), 89–96. https://doi.org/10.1016/s0026-0495(97)90174-8
- Khorram, O., Laughlin, G. A., & Yen, S. S. (1997). Endocrine and metabolic effects of long-term administration of [Nle27] growth hormone-releasing hormone-(1-29)-NH2 in age-advanced men and women. The Journal of clinical endocrinology and metabolism, 82(5), 1472–1479. https://doi.org/10.1210/jcem.82.5.3943
- Gobburu, J. V., Agersø, H., Jusko, W. J., & Ynddal, L. (1999). Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers. Pharmaceutical research, 16(9), 1412–1416 https://doi.org/10.1023/a:1018955126402
- 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
- Khorram, O., Laughlin, G. A., & Yen, S. S. (1997). Endocrine and metabolic effects of long-term administration of [Nle27]growth hormone-releasing hormone-(1-29)-NH2 in age-advanced men and women. The Journal of clinical endocrinology and metabolism, 82(5), 1472–1479. https://doi.org/10.1210/jcem.82.5.3943
- 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
- Image 1 (Sermorelin) Source: https://pubchem.ncbi.nlm.nih.gov/compound/Sermorelin
- Image 2 (Ipamorelin) Source: https://pubchem.ncbi.nlm.nih.gov/compound/Ipamorelin