MGF
A locally acting IGF-1 splice variant that switches muscle satellite cells out of quiescence to drive the earliest phase of muscle repair after mechanical loading.
MGF (Mechano Growth Factor), 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. It acts 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. Native MGF has an extremely short serum half-life (roughly 5-7 minutes), so research suppliers typically offer PEG-MGF, a pegylated form with extended action. MGF is a research compound with no regulatory approval and no established human clinical pharmacokinetic or safety data.
Class
Locally acting IGF-1 splice variant (non-PEGylated Mechano Growth Factor peptide)
Half-life
~5-7 minutes native; ~24-48 hours as PEG-MGF
Routes
Intramuscular, Subcutaneous
Category
Growth Hormone & Performance
Researched benefits
What it's studied for
Satellite cell activation
MGF drives skeletal muscle satellite (stem) cells out of quiescence and into the cell cycle following mechanical loading, initiating the earliest phase of muscle repair more rapidly than systemic IGF-1. This is its most consistently documented preclinical effect.
Local autocrine/paracrine repair signal
Unlike endocrine IGF-1, MGF acts locally at the site of muscle damage, functioning as an autocrine/paracrine signal that coordinates the initial repair response. Its unique C-terminal E-peptide domain is proposed to be the bioactive moiety responsible for this action.
Progenitor cell proliferation and fusion
In primary human muscle cell cultures, the MGF E-peptide extended the proliferative lifespan of satellite cells and enhanced their fusion potential across different age groups, supporting a role in muscle regeneration.
Post-exercise hypertrophy candidate
By activating satellite cells and promoting myonuclear donation into existing fibers, MGF is studied as a candidate for post-exercise hyperplasia/hypertrophy protocols, particularly during the lag phase before satellite cells proliferate and fuse.
Tissue repair adjunct
MGF is investigated as an adjunct for repair of muscle and tendon tissue, capitalizing on its role in the early injury-response window.
Potential role in age-related muscle decline
MGF expression after mechanical loading is reduced in aged muscle relative to young tissue, and this deficit has been proposed as a contributing factor to age-related sarcopenia, making synthetic MGF a research candidate for countering declining regenerative capacity.
Mechanism
How it works
Skeletal muscle exposed to mechanical stress triggers alternative splicing of the IGF-1 gene, producing the IGF-1Ec isoform (MGF) rather than the systemic IGF-1Ea variant. This makes MGF a stress-responsive, locally produced signal distinct from circulating growth hormone-driven IGF-1.
MGF acts at the site of muscle microdamage to activate satellite cells, driving them out of quiescence into the cell cycle. The result is increased proliferation of muscle progenitor cells and their eventual fusion into existing myofibers (myonuclear donation), a process central to muscle repair and hypertrophy.
The unique C-terminal E-peptide domain of MGF is proposed to be the bioactive moiety responsible for satellite cell activation, acting at least partially independently of the IGF-1 receptor and specific to the mechanical stress response rather than to systemic growth signaling. This mechanistic separation distinguishes MGF's early repair function from the later differentiation role mediated by the mature IGF-I isoform.
Native MGF is rapidly degraded in circulation (half-life on the order of minutes), which limits duration of action after exogenous administration. PEG-MGF conjugates polyethylene glycol to the peptide to extend its biological half-life to roughly one to two days, the same stabilization technology used for other therapeutic proteins; PEG-MGF is the more commonly studied variant in animal myopathy models for this reason.
Dosing protocols
Dosing & administration
Dosing reflects protocols reported in research and community literature for educational purposes. It is not medical advice or a recommendation. Most peptides here are not approved for human use.
Reconstitution
Reconstitute with bacteriostatic water. A 2 mg vial + 1 mL BAC water = 2000 mcg/mL, so 5 units (0.05 mL) on an insulin syringe delivers 100 mcg. Refrigerate after mixing and use within 28 days.
Beginner
- Dose
- 100 mcg (PEG-MGF)
- Frequency
- 2x per week
- Timing
- Post-workout
- Duration
- 4 weeks
- Route
- Intramuscular
Entry-level protocol into the trained muscle following exercise.
Intermediate
- Dose
- 200 mcg (PEG-MGF)
- Frequency
- 2-3x per week
- Timing
- Post-workout
- Duration
- 6 weeks
- Route
- Intramuscular or subcutaneous
Often paired with creatine and adequate protein intake for synergy.
Advanced
- Dose
- 300 mcg (PEG-MGF)
- Frequency
- 3x per week
- Timing
- Post-workout, at injury or hypertrophy target site
- Duration
- 4-6 weeks
- Route
- Intramuscular
Injected at the target muscle or injury site; typically run 4-6 weeks on, 4 weeks off.
- Native MGF must be injected immediately post-workout into the trained muscle because of its 5-7 minute half-life; PEG-MGF can be dosed within hours of training and circulates far longer.
- Reported dose range is 100-300 mcg per injection (PEG-MGF), 2-3x per week post-workout.
- Cycle guidance is 4-6 weeks per cycle followed by roughly 4 weeks off.
- No human clinical pharmacokinetic or safety data has been established for either native MGF or PEG-MGF; all dosing is derived from community and preclinical research contexts.
Evidence
Research & clinical studies (2)
Mechano Growth Factor E peptide (MGF-E), derived from an isoform of IGF-1, activates human muscle progenitor cells and induces an increase in their fusion potential at different ages
In primary human muscle cell cultures, the MGF-E peptide significantly extended the proliferative lifespan of satellite cells from neonatal and young adult donors and enhanced their fusion potential across all age groups, suggesting synthetic MGF could help counter age-related decline in muscle regenerative capacity.
PMID 21354439Minireview: Mechano-growth factor: a putative product of IGF-I gene expression involved in tissue repair and regeneration
Summarizes evidence that MGF, an IGF-I splice variant up-regulated by mechanical stress in skeletal muscle, plays a distinct role in satellite cell and myoblast proliferation during the early phase of the muscle injury response, separate from the mature IGF-I isoform that mediates later differentiation.
PMID 20130113Combinations
Stacking & blends
MGF + Creatine + Protein
Support hypertrophy and recovery
Pairing MGF with creatine and adequate protein intake is suggested at the intermediate tier to provide substrate and cellular support alongside satellite cell activation.
MGF with IGF-1 LR3 (caution)
Combined growth-factor signaling
MGF and IGF-1 LR3 have overlapping growth-factor activity; sources flag this combination as requiring caution rather than recommending it, given additive IGF signaling.
Safety
Side effects & considerations
Commonly reported effects
Contraindications & cautions
- Active malignancy or cancer history (relative)
- Elevated IGF-1
- Pregnancy and breastfeeding
- Active diabetic ketoacidosis
- Caution with concurrent IGF-1 LR3 due to overlapping growth-factor activity
MGF carries a moderate risk profile in research contexts. Because it is a growth factor, there is a theoretical risk in active malignancy. No long-term human safety data exists. Review contraindications and consult a qualified professional before use.
FAQ
MGF — common questions
What is MGF?
MGF (Mechano Growth Factor), also called IGF-1Ec, is a splice variant of the IGF-1 gene produced locally in skeletal muscle in response to mechanical loading and tissue microdamage. It acts as an autocrine/paracrine signal that activates muscle satellite cells to initiate the early repair response, distinct from the endocrine actions of systemic IGF-1.
How is MGF different from PEG-MGF?
Native MGF has a very short serum half-life (about 5-7 minutes), which limits its duration after injection. PEG-MGF is a pegylated version with polyethylene glycol conjugated to the peptide to extend half-life to roughly 24-48 hours. Research suppliers often offer both; PEG-MGF is the more commonly studied form. Neither has human clinical data.
What is MGF primarily studied for?
It is studied for muscle satellite cell activation following mechanical loading, as a local muscle repair signal distinct from systemic IGF-1, and for progenitor cell proliferation and fusion in vitro. It is a candidate for post-exercise hypertrophy and tissue repair research.
How is MGF dosed in research protocols?
Reported protocols use 100-300 mcg of PEG-MGF, 2-3 times per week post-workout, over cycles of about 4-6 weeks. Beginner protocols start at 100 mcg twice weekly; advanced protocols use 300 mcg three times weekly at the target muscle. Native MGF must be injected immediately post-workout into the trained muscle due to its short half-life.
How do I reconstitute MGF?
Reconstitute with bacteriostatic water. A 2 mg vial plus 1 mL of BAC water yields 2000 mcg/mL, so 5 units (0.05 mL) delivers 100 mcg. Refrigerate after mixing and use within 28 days.
What are the side effects of MGF?
Commonly reported effects include injection site irritation, transient hypoglycemia, and mild water retention. It is contraindicated with active or prior malignancy, elevated IGF-1, pregnancy and breastfeeding, and diabetic ketoacidosis, and should be used cautiously alongside IGF-1 LR3.
Is MGF legal or approved?
No. MGF has no FDA approval and has not been evaluated by the FDA. It is sold as a research chemical only and is prohibited by WADA for athletes.
