Ghrelin vs MGF

Must be acylated at Ser3 (by GOAT enzyme) for GHSR-1a binding. Receptor activation in the pituitary stimulates GH release; hypothalamic action via NPY/AgRP neurons increases appetite and reduces energy expenditure.

Ghrelin is an endogenous 28-amino-acid peptide hormone produced primarily by X/A-like cells of the gastric fundus, characterized by a unique octanoyl modification at Ser3 required for GHS-R1a receptor binding; it is the endogenous ligand for the growth hormone secretagogue receptor and functions as a dual regulator of GH secretion and energy homeostasis. Ghrelin acts centrally via hypothalamic GHS-R1a receptors to potently stimulate GH release from the pituitary and to promote appetite through NPY/AgRP pathway activation, and has peripheral effects on gastric motility and insulin secretion, establishing it as a key integrator of nutritional status, GH axis activity, and energy balance. The pharmacology of GHS-R1a activation in humans is validated through macimorelin (Macrilen), an FDA-approved oral ghrelin receptor agonist; Phase 1 and Phase 2 randomized controlled trials of macimorelin demonstrated robust and reliable GH stimulation in adults, supporting FDA approval in 2017 for the diagnosis of adult GH deficiency and confirming the human physiological relevance of ghrelin receptor activation. Ghrelin itself is not therapeutically administered; it has a very short plasma half-life and the active acylated form is rapidly degraded in circulation; FDA-approved ghrelin receptor agonists require prescription and are indicated for diagnostic rather than therapeutic use, while ghrelin peptide is used exclusively as a research tool compound in neuroendocrine pharmacology studies.

Splice variant of IGF-1; acts locally at site of muscle damage to activate satellite cells (muscle stem cells) for repair and hypertrophy

Mechano growth factor (MGF), also designated IGF-1Ec, is a splice variant of the IGF-1 gene produced locally in skeletal muscle in response to mechanical loading and tissue microdamage, and is proposed to function as an autocrine/paracrine signal that activates muscle satellite cells and initiates the early repair response, a role distinct from the endocrine actions of systemic IGF-1. The unique C-terminal E-peptide domain of MGF is proposed to be the bioactive moiety responsible for satellite cell activation and progenitor cell proliferation, acting through mechanisms that are at least partially independent of IGF-1R and specific to the mechanical stress response rather than systemic growth signaling. Human muscle progenitor cell studies have demonstrated that the MGF E-peptide activates muscle progenitor cells and enhances their fusion potential across different age groups, suggesting a role in the age-related decline in muscle repair capacity. MGF is a research compound with no regulatory approval in any jurisdiction; exogenous administration is investigational, no human clinical pharmacokinetic or safety data has been established, and published evidence is limited to in vitro and preclinical contexts. MGF vs PEG-MGF: native MGF has a very short half-life in circulation, limiting its duration of action after exogenous administration. PEG-MGF (pegylated MGF) is a chemically stabilized version in which polyethylene glycol is conjugated to the peptide to extend its biological half-life — the same technology used to extend the half-life of therapeutic proteins such as PEG-EPO. Research compound suppliers often offer both forms; PEG-MGF is the more commonly studied variant in animal myopathy models for this pharmacokinetic reason. Neither form has human clinical data. MGF in muscle research: interest in MGF as a research compound centers on its proposed role in the lag phase of muscle repair following eccentric exercise-induced damage — the window when satellite cells are activated before proliferating and fusing into existing myofibers. In aged muscle, MGF expression following mechanical loading is reduced relative to young tissue, and this deficit has been proposed as a contributing factor to age-related sarcopenia in the research literature. Providers offering research peptides in the performance and recovery category are listed in the PeptideBase directory.