Compound profile
MGF (Mechano Growth Factor)
EmergingAlso known as: IGF-1Ec · IGF-1Eb (rodent) · Mechano growth factor
A splice variant of IGF-1 that muscle tissue produces locally in response to mechanical stretch, stimulation, or injury. Studied mainly in animal and cell models of muscle repair and regeneration; sold as a synthetic research peptide despite very limited direct human data.
Overview
MGF is not a separate hormone but an alternative splice variant of the IGF-1 gene, meaning the body's own cells produce it by reading the IGF-1 gene differently under certain conditions. Researchers first identified this stretch-induced isoform in rabbit skeletal muscle in the late 1990s, distinguishing it from the liver-derived IGF-1Ea that circulates systemically, and named it mechano growth factor because muscle tissue only ramps up its production in response to mechanical loading, stretch, or damage.
Because of that local, injury-triggered expression pattern, MGF has been studied mainly as a signal for muscle repair and satellite cell activation, the process by which muscle stem cells are recruited to rebuild damaged fibers. This body of research is almost entirely preclinical, based on animal muscle models, cell culture, and a smaller amount of human muscle biopsy work looking at gene expression after exercise, not on injecting synthetic MGF into people.
The synthetic peptide sold under the name MGF in research-chemical markets is a lab-made version of the carboxy-terminal fragment of this splice variant. It has an extremely short half-life in circulation, on the order of minutes, which has driven interest in the pegylated version, PEG-MGF, as a longer-acting alternative, though that modification carries its own separate and even thinner evidence base.
Mechanism (plain language)
Locally produced in mechanically stressed or damaged muscle, where it is thought to activate satellite (muscle stem) cells and promote their proliferation, an early step in muscle repair and hypertrophy that differs from the muscle-maturation role of liver-derived systemic IGF-1.
How it works
When skeletal muscle is stretched, loaded, or damaged, local tissue shifts how it splices the IGF-1 gene, producing this alternate isoform instead of, or alongside, the liver-type IGF-1Ea that circulates in blood. Preclinical work suggests MGF's distinct carboxy-terminal E-domain peptide, once cleaved from the parent molecule, acts locally to activate quiescent satellite cells, the muscle-resident stem cells that proliferate and then differentiate to repair or add muscle fibers. This is proposed as an early-response signal, distinct from the later role systemic IGF-1 plays in helping those activated cells mature and fuse into muscle fibers.
Human muscle biopsy studies after resistance exercise have found expression of the IGF-1Ec splice variant increases in exercised muscle, including in older adults, supporting the idea that this pathway is physiologically active in humans. However, that is expression of the body's own gene product after exercise, not evidence about what happens when a synthetic peptide fragment is injected, which is a distinct and far less studied question.
What research suggests
Animal and cell-culture studies consistently link MGF expression to satellite cell activation and muscle repair after mechanical damage. There is essentially no controlled human data on injecting the synthetic peptide fragment sold under this name.
Reported benefits
What studies, case reports, and the research literature describe, not guaranteed outcomes. The trials behind these findings are in the studies below.
Satellite cell activation in animal and cell models
Preclinical studies link MGF expression after muscle stretch or damage to proliferation of satellite cells, the muscle-resident stem cells involved in repair and hypertrophy.
Confirmed expression in human muscle after exercise
Biopsy studies report that IGF-1Ec splice variant expression rises in human skeletal muscle after high-resistance exercise, including in older adults, supporting that this pathway is physiologically active in people even though the injectable peptide itself remains untested.
Uncertainties & risks
Nearly all the underlying science describes the body's own gene splicing response to exercise or injury, not the pharmacology of the injected synthetic peptide, which has an extremely short half-life and no established human dosing or safety data. As an IGF-1-related growth factor, it carries the same theoretical long-term concerns about cell proliferation as other IGF-axis peptides.
The gap between what has actually been studied, the body's own splice-variant expression after exercise, and what is sold as an injectable research peptide is unusually wide for MGF, and that distinction should shape how the existing evidence is read. Because native MGF acts locally and degrades within minutes, it's unclear how much of that biology is reproduced by injecting a synthetic fragment into the bloodstream rather than having it produced in situ by mechanically stressed tissue. No controlled human trials have tested injectable MGF for muscle growth, recovery, or any other outcome, and safety data specific to the synthetic peptide does not exist.
STACKD study summaries
Start with our in-house roundups, plain-language synthesis of the research, with primary sources cited at the bottom of each.
Primary sources
Secondary citations for verification. Prefer the STACKD summary above for context before opening these.