GHRP-2 (Growth Hormone Releasing Peptide 2) â Research Overview
Introduction
GHRP-2 (pralmorelin) is a synthetic pentapeptide and growth hormone-releasing peptide (GHRP) that acts as an agonist of the ghrelin (growth hormone secretagogue) receptor, GHS-R1a. Although structurally related to met-enkephalin, GHRP-2 lacks neurotransmitter-like effects and instead engages endocrine pathways to stimulate growth hormone (GH) secretion. Beyond the pituitary, GHS-Rs are distributed in the hypothalamus and peripheral tissues, linking GHRP-2 to research on appetite, metabolism, inflammation, and tissue protection.
Mechanisms of Action
GHRP-2 binds GHS-R1a, a G proteinâcoupled receptor, initiating intracellular cascades that can include activation of GÎąq/11, phospholipase C (PLC), and hydrolysis of PIP2 into IP3 and DAG. IP3 mobilizes intracellular Ca2+, while DAG activates protein kinase C (PKC); together these signals promote GH exocytosis from pituitary somatotrophs. In some models, cAMP generation further amplifies GH synthesis. Receptor desensitization has been observed shortly after exposure, with sensitivity recovering within several hours.
Centrally, GHRP-2 may influence appetite-regulating neurons by enhancing orexigenic neuropeptides (NPY/AgRP), inhibiting anorexigenic Îą-MSH signaling, and engaging mesolimbic reward circuitryâmechanisms consistent with ghrelin-like increases in food intake.
Chemical Characteristics
| Compound | Type | Molecular Formula | Molecular Weight |
| GHRP-2 | Synthetic growth hormone secretagogue (hexapeptide) | Cââ Hâ â NâOâ | 818.0 g/mol |
Other Titles: Pralmorelin
Research Applications
1. Growth Hormone / IGF-1 Secretion
â Comparative studies reported that GHRP-2 elicits greater GH peaks than native GHRH and can co-elevate prolactin, ACTH, and cortisol in some settings.- Reported findings include: up to ~181-fold higher acute GH spikes versus baseline in cell/organ models; ~47-fold increases in mean 2.5âhour pulsatile GH output versus placebo; and sustained regimens yielding ~3â5Ă GH elevations with IGFâ1 rising from ~100 Îźg/L to ~180 Îźg/L.
2. Appetite and Energy Intake
â In controlled buffet-style paradigms, GHRP-2 exposure increased caloric intake by ~36% versus saline, with energy intake per kg rising to approximately 136 kJ/kg compared with ~101 kJ/kg in controls. GH areaâunderâcurve also increased markedly in parallel.
3. Muscle Catabolism and Tissue Protection (Preclinical)
â Thermalâinjury murine models suggest reductions in inflammatory markers (e.g., ILâ6) and muscle atrophy mediators (MuRFâ1, MAFbx), with indications of lowered muscle protein breakdown. Case observations have described associated weight and lean mass gains.
4. Oxidative Stress, Atherogenic Signaling, and Inflammation
â In ApoEâ/â mice, prolonged GHRP-2 exposure was linked to higher circulating IGFâI, reduced aortic superoxide production, and lower expression of proâoxidant/proâinflammatory genes (e.g., 12/15âlipoxygenase, interferonâÎł, MIF). Cell studies indicate protection against OxLDLâinduced peroxide production, IGFâI receptor suppression, and apoptosis, as well as reduced macrophage lipid loading.- In acute lungâinjury models, GHRPâ2 reduced edema, neutrophil infiltration, and proâinflammatory cytokines, with evidence of dampened NFâÎşB activation.
5. Diagnostic Applications in GH Deficiency (Research Use)
â As an alternative to insulin tolerance testing, GHRPâ2 has been evaluated as a provocative agent: postâfasting administration produced reproducible GH peaks within ~1 hour across cohorts previously characterized by ITT. In pediatric or developing models of GH deficiency, GHRPâ2 alone and in combination with GHRH elicited robust GH responses.
6. Combination Studies (TRH, GnRH)
â In prolonged hypoâsomatotropism/hypogonadism/hypothyroid research models, combined GHRPâ2 + TRH + GnRH regimens produced the greatest activation across GH, TSH, and LH axes relative to GHRPâ2 alone or GHRPâ2 + TRH.
Practical Considerations in Models
â Rapid receptor desensitization suggests spacing between exposures may influence outcomes.- Offâaxis endocrine effects (ACTH/cortisol, prolactin) have been observed and may be modelâdependent.
Conclusion
GHRPâ2 is a ghrelinâreceptor agonist investigated for robust GH/IGFâ1 stimulation, orexigenic effects, and potential tissueâprotective, antiâinflammatory, and antioxidative properties across preclinical and clinical paradigms. Its use as a GHâprovocative agent has also been explored. Outcomes vary with dose, timing, model, and combination protocols.
GHRP-2 (Growth Hormone Releasing Peptide-2) â References
- Bowers, C. Y., Reynolds, G. A., Durham, D., Barrera, C. M., Pezzoli, S. S., Thorner, M. O. Growth hormoneâreleasing peptide stimulates GH release in normal men and acts synergistically with GHRH. Journal of Clinical Endocrinology & Metabolism. 1990;70(4):975â982. https://doi.org/10.1210/jcem-70-4-975
- Bowers, C. Y. GHâreleasing peptides â structure and kinetics. Journal of Pediatric Endocrinology & Metabolism. 1998;11(2):199â205. https://doi.org/10.1515/jpem.1998.11.2.199
- Bowers, C. Y., Momany, F. A., Reynolds, G. A., Hong, A. On the in vitro and in vivo activity of a new synthetic hexapeptide that acts on the pituitary to specifically release growth hormone. Endocrinology. 1984;114(5):1537â1545. https://doi.org/10.1210/endo-114-5-1537
- Thorner, M. O., Chapman, I. M., Cella, S. G., Davis, J., Vance, M. L., Bowers, C. Y. The growth hormone-releasing peptides: clinical studies. Endocrine Reviews. 1997;18(5): 648â672. https://doi.org/10.1210/edrv.18.5.0313
- Ghigo, E., Arvat, E., Gianotti, L., Imbimbo, B. P., Lenaerts, V., Deghenghi, R., Camanni, F. Growth hormone-releasing hormone combined with GHRP-2 strongly stimulates GH release in normal and obese subjects, elderly individuals, and patients with GH deficiency. Journal of Clinical Endocrinology & Metabolism. 1994;79(5): 1264â1268. https://doi.org/10.1210/jcem.79.5.7962326
- Arvat, E., Di Vito, L., Maccario, M., Broglio, F., Benso, A., Gottero, C., Papotti, M., Muccioli, G., Dieguez, C., Casanueva, F. F., Deghenghi, R., Camanni, F., Ghigo, E. Endocrine activities of ghrelin, a natural growth hormone secretagogue (GHS), in humans: comparison and interactions with GHRP-2 and GHRH. Journal of Clinical Endocrinology & Metabolism. 2001;86(2): 1169â1174. https://doi.org/10.1210/jcem.86.2.7207
- Camanni, F., Ghigo, E., Arvat, E. Growth hormone-releasing peptides and their analogues. Baillièreâs Clinical Endocrinology and Metabolism. 1998;12(3): 383â398. https://doi.org/10.1016/S0950-351X(98)80009-0
- Jacks, T., Hickey, G. J., Judith, F., Schneider, H., Bowers, C. Y., Thorner, M. O. Effects of intravenous GHRP-2 on GH secretion in elderly and young adults. Journal of Clinical Endocrinology & Metabolism. 1995;80(11): 3209â3215. https://doi.org/10.1210/jcem.80.11.7593437
- Poehlman, E. T., Copeland, K. C., Bowers, C. Y. Influence of growth hormone-releasing peptide on metabolic function in older individuals. Metabolism. 1994;43(10): 1336â1341. https://doi.org/10.1016/0026-0495(94)90056-6
- Svensson, J., LĂśnn, L., Jansson, J. O., Murphy, G., Bengtsson, B. A. Two-week treatment with GHRP-2 in GH-deficient adults increases 24-hour GH secretion. Clinical Endocrinology. 1997;46(4): 425â430. https://doi.org/10.1046/j.1365-2265.1997.1600942.x
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