GHRP-2 Peptide
GHRP-2 is a synthetic peptide made of five amino acids (pentapeptide) analogous to the endogenous neurotransmitter met-enkephalin.(1) Yet, the peptide appears to lack any neurotransmitter-like properties and instead appears to activate the receptors for the hormone ghrelin. Ghrelin is a naturally occurring hormone that is posited to regulate food intake.(11) Growth hormone-releasing peptide GHRP-2 may induce the secretion of growth hormone (GH) by apparently activating the ghrelin receptors on the pituitary gland, also termed as growth hormone secretagogue receptors (GHS-Rs).Overview of GHRP-2 Mechanisms
Bovine studies have suggested that GHRP-2 peptide exhibits multifaceted impacts, but its main mechanism of action appears to involve the GHS-Rs. These receptors are naturally triggered by ghrelin and may be found in various parts of the nervous system and other tissues. In the nervous system, they are located in the hypothalamus and the pituitary, among other structures. When GHRP-2 appears to engage with GHS-Rs, it’s believed that a structural transformation might be triggered upon attachment, possibly initiating intracellular signaling networks primarily mediated through G-proteins. The release of Gαq/11, a component of the G-proteins, might commence, potentially setting off subsequent signaling sequences. Phospholipase C (PLC) may split phosphatidylinositol 4,5-bisphosphate (PIP2) into secondary signaling molecules, IP3 and DAG (diacylglycerol). IP3 is thought to prompt the release of calcium ions. In contrast, DAG may activate protein kinase C (PKC), potentially heightening the signaling pathway and possibly facilitating the secretion of growth hormone from pituitary cells. Moreover, this process may also involve the activation of cyclic AMP (cAMP), which plays a crucial role in cellular signaling. Increasing cAMP levels may further enhance the signaling cascade, potentially boosting GH synthesis.(13)(14) Nevertheless, GHRP-2 appears to induce desensitization at these receptors immediately after exposure, potentially reducing sensitivity lasting a complete four hours before reversal.(5) By apparently activating the GHS-Rs on other parts of the nervous system, GHRP-2 might trigger a series of cellular events leading to the enhanced synthesis of hunger-promoting neuropeptides, namely Neuropeptide Y (NPY) and Agouti-related peptide (AgRP). These peptides are thought to be integral to the regulation of energy balance and the control of appetite. At the same time, GHRP-2 is believed to possibly inhibit the secretion of the appetite-reducing hormone, melanocyte-stimulating hormone (α-MSH), thus shifting the equilibrium towards increased hunger and encouraging dietary intake. Moreover, GHRP-2 might affect the mesolimbic reward system, a neural pathway associated with regulating the craving for food, via the activation of GHSR-1a receptors. This action might theoretically heighten the drive for food consumption, potentially through the activation of cyclic adenosine monophosphate (cAMP) pathways, further implicating GHRP-2 in the modulation of feeding behavior and reward-based eating.Chemical Makeup
Molecular Formula: C45H55N9O6 Molecular Weight: 817.97 g/mol Other Known Titles: pralmorelinResearch and Clinical Studies
GHRP-2 Peptide and Growth Hormone Synthesis
This study(7) was conducted to understand the action of two synthetic GHRPs, GHRP-2 and Hexarelin (HEX), on growth hormone, prolactin, adrenocorticotropic hormone (ACTH), and cortisol concentrations. Two groups of various stages of mature development were evaluated, and both groups experienced a higher GH increase compared to the physiological increase induced by native growth hormone-releasing hormone (GHRH). Unfortunately, GHRP-2 also may induce an apparent increase in the levels of ACTH and cortisol. Further studies have reported that exposure to GHRP-2 in laboratory settings may induce a significant increase in peak GH levels, mean pulsatile GH secretion by the anterior pituitary gland cells, and may potentially upregulate mediators of GH’s anabolic actions such as insulin-like growth factor-1 (IGF-1):- In one trial, GHRP-2 was suggested to induce up to 181-fold higher spike in GH production by the anterior pituitary gland cells.(17)
- Another experiment posited that the peptide may induce a 47-fold increase in mean 2.5-hour pulsatile GH secretion by the anterior pituitary gland cells compared to placebo.(18)
- A third trial on prolonged GHRP-2 exposure reported that the peptide may have induced an apparent increase in GH levels between 3-fold and 5-fold. Moreover, IGF-1 levels apparently increased from an average of 100mcg/l at baseline to a plateau value of around 180mcg/l.(19)




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