Quick summary
MGF (Mechano Growth Factor / IGF-1Ec) is a splice variant of IGF-1 produced locally in muscle after mechanical loading or injury. It specifically activates quiescent satellite cells for muscle repair and hypertrophy, working through a unique E-peptide that does not bind the IGF-1 receptor.
Overview
MGF (Mechano Growth Factor), also designated IGF-1Ec, is a splice variant of insulin-like growth factor 1 (IGF-1) produced locally in muscle tissue in response to mechanical loading and injury. Unlike systemic IGF-1, MGF is transiently expressed at the site of damage and specifically activates quiescent muscle satellite cells — the resident stem cells responsible for muscle repair and hypertrophy. It is used in research and by athletes interested in accelerating muscle recovery.
Mechanism of action
MGF arises from alternative splicing of the IGF-1 gene: a 49-base-pair insert in exon 5 causes a reading frame shift, producing a unique carboxy-terminal E-domain peptide (the MGF E-peptide) that does not bind the IGF-1 receptor and signals through distinct, incompletely characterized pathways. When muscle fibers are subjected to mechanical strain or damage, the IGF-1 gene is preferentially spliced toward the MGF (IGF-1Ec/Eb) isoform. The resulting MGF E-peptide activates quiescent satellite cells — inducing proliferation without differentiation — expanding the progenitor pool available for repair. Mature IGF-1 (primarily IGF-1Ea splice variant) then drives satellite cell differentiation, fusion into existing fibers, and net fiber hypertrophy. This two-phase sequence (MGF: proliferate; IGF-1Ea: differentiate) explains why exogenous MGF, timed post-exercise or post-injury, may amplify the hypertrophic response. Pegylated MGF (PEG-MGF) extends the very short half-life of the native peptide from minutes to days.
Dosing protocols
| Purpose | Route | Dosage | Frequency | Notes |
|---|---|---|---|---|
| Muscle recovery / satellite cell activation | intramuscular | 200–400 mcg | 2-3x per week post-workout | Native MGF has a very short half-life (~minutes). Many researchers prefer PEG-MGF for extended action. Inject near the worked muscle group post-exercise. |
| PEG-MGF muscle recovery | subcutaneous | 200–400 mcg | 2-3x per week | PEG-MGF extends half-life significantly, allowing less frequent dosing. Subcutaneous or intramuscular administration. |
Dosing information is for educational purposes only. Consult a qualified healthcare professional before using any peptide.
Research summary
In vitro, the MGF E-peptide significantly increases satellite cell proliferative lifespan and delays senescence at concentrations as low as 3 ng/ml, with maximal effect around 100 ng/ml. Animal studies demonstrate that MGF injection post-muscle injury accelerates fiber repair and increases cross-sectional area in rodent models. A 2017 Molecular Brain study showed MGF promotes neurogenesis in aging mice, suggesting neuroprotective properties beyond muscle. No human clinical trials have been completed. Most human-relevant data comes from in vitro cell culture experiments with primary human satellite cells, which confirm MGF-E peptide activation at multiple age groups.[1][2][3][4][5]
Evidence grading
Each claimed benefit is graded by the strength of available evidence. Grades reflect study quality, not effect size.
Strong = multiple RCTs · Moderate = limited trials or observational · Preliminary = animal or in vitro only · Insufficient = anecdotal or no published data
Side effects
Side effects vary by individual. This is not an exhaustive list. Report unusual symptoms to a healthcare professional.
Common stacks
Peptides commonly paired with MGF for synergistic effects.
Legal status
MGF and PEG-MGF are unscheduled research chemicals with no FDA-approved medical use. Not approved for human administration. Sold legally as research chemicals in many jurisdictions, though the same FDA enforcement actions affecting other peptides have affected MGF availability in the US. Prohibited by WADA in competitive sport.
Sourcing & access
Research compound
MGF is classified as a research compound. Regulatory status varies by jurisdiction. Always verify current legal status and source from vendors providing third-party certificates of analysis (COA).
Frequently asked questions
MGF (Mechano Growth Factor), designated IGF-1Ec, is an IGF-1 splice variant produced locally in muscle tissue in response to mechanical strain or injury. Unlike systemic IGF-1, it specifically activates quiescent satellite cells (muscle stem cells) for repair and growth.
When muscle is strained or damaged, the IGF-1 gene is spliced toward the MGF isoform. The MGF E-peptide activates satellite cells, inducing proliferation without differentiation. Mature IGF-1 then drives differentiation and fiber fusion. This two-phase sequence (MGF: proliferate, IGF-1: differentiate) enables the hypertrophic response.
Side effects include injection site pain or swelling, theoretical hypoglycemia risk (shared with the IGF-1 family), local tissue growth with repeated IM injection, headache, and fatigue. No human clinical trials have been completed and long-term effects are unknown.
Native MGF has an extremely short half-life of minutes, while PEG-MGF (pegylated form) extends the half-life to several days through pegylation. PEG-MGF allows less frequent dosing (2-3x weekly subcutaneously) versus native MGF which is typically injected intramuscularly post-workout.
Research references
- Minireview: Mechano-growth factor: a putative product of IGF-I gene expression involved in tissue repair and regenerationReview
- 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 agesPubMed
- Mechano growth factor promotes proliferation and inhibits differentiation of porcine satellite cells by down-regulation of key myogenic transcriptional factorsPubMed
- Mechano growth factor, a splice variant of IGF-1, promotes neurogenesis in the aging mouse brainPubMed
- Impairment of IGF-I gene splicing and MGF expression associated with muscle wastingPubMed