MGF
A splice variant of IGF-1 (IGF-1Ec) produced by muscle in response to mechanical stress, thought to help activate muscle repair. PEG-MGF is a longer-lasting pegylated version. Evidence is largely preclinical; it is a research compound, not an approved drug.
Quick take
- What it is: a splice variant of IGF-1 (called IGF-1Ec) made by muscle after mechanical stress; PEG-MGF is a longer-lasting pegylated form.
- What people use it for: muscle repair and recovery, based on its proposed role in activating muscle stem (satellite) cells.
- What we actually know: most evidence is preclinical; controlled human data on injected MGF is essentially absent.
- Status: a research compound, not FDA-approved, and prohibited in sport.
What it is
MGF — Mechano Growth Factor — is a splice variant of insulin-like growth factor 1 (IGF-1), formally known as IGF-1Ec. Muscle tissue produces it locally in response to mechanical loading or damage, where it is thought to help kick off the early stages of repair.1 Because it is a naturally occurring splice product, the synthetic peptides sold under this name are attempts to reproduce that local signal.
Natural MGF is cleared from the body very rapidly. To address this, a pegylated variant — PEG-MGF (Peg-MGF) — attaches a polyethylene-glycol molecule that slows clearance and extends its half-life. PEG-MGF is the form most often discussed for injection.
How it works
The proposed mechanism is the activation of muscle satellite cells — the resident stem cells that fuse with muscle fibres to support growth and repair after mechanical stress.1,2 In this model, MGF acts as an early, local trigger distinct from the systemic, liver-derived form of IGF-1. This is a biologically interesting idea, but how completely it translates to a benefit from injected MGF in humans is unestablished.
What the evidence shows
Animal & cell studies
Most of what is known comes from cell-culture and animal studies of the body’s own locally produced MGF, which support a role in satellite-cell activation and early muscle repair.2 These findings are the basis for the compound’s reputation.
Human studies
Controlled human trials of injected synthetic MGF or PEG-MGF are essentially absent. The single most important point is that the appealing muscle-repair story rests on the body’s endogenous, locally acting factor — not on demonstrated benefit from administering the peptide exogenously.3 Reports of benefit are largely theoretical or anecdotal.
Dosages reported in the literature
Informational only. The figures below describe doses reported informally rather than in controlled human trials. They are not a recommendation or a prescription, and appropriate use, if any, should be determined by a qualified healthcare professional who can account for your individual situation.
| Setting | Route | Reported range |
|---|---|---|
| Cell / animal research | Various | Not directly applicable to humans |
| Anecdotal (PEG-MGF) | Subcutaneous / intramuscular | Reported in microgram amounts, sometimes timed around training |
Because there are no dose-finding human trials, no range here should be read as established as safe or effective. Reported protocols vary widely between sources.
Safety & side effects
There is no meaningful long-term human safety data for injected MGF or PEG-MGF. As a member of the IGF-1 family, it raises the same theoretical concerns associated with stimulating growth pathways — including effects on tissue growth and metabolism — that warrant caution in the absence of controlled data.3 Injection-site reactions are plausible.
A practical concern in the unregulated market is product quality. Purity, dose accuracy and the actual identity of the peptide vary between sources.
Legal & regulatory status
MGF / PEG-MGF is not approved by the FDA for any use and is best described as a research compound. As an IGF-1-related growth factor, it is prohibited in sport at all times by the World Anti-Doping Agency (category S2, peptide hormones, growth factors and related substances).4 Rules vary by country and change over time.
References
- Matheny RW Jr, Nindl BC, Adamo ML. Minireview: Mechano-Growth Factor: A Putative Product of IGF-I Gene Expression Involved in Tissue Repair and Regeneration. Endocrinology. 2010;151(3):865-875. [PMID 20130113, doi:10.1210/en.2009-1217]
- Matheny RW Jr, Nindl BC, Adamo ML. Minireview: Mechano-Growth Factor: A Putative Product of IGF-I Gene Expression Involved in Tissue Repair and Regeneration. Endocrinology. 2010;151(3):865-875. [PMID 20130113, doi:10.1210/en.2009-1217]
- Fornaro M, Hinken AC, Needle S, et al. Mechano-growth factor peptide, the COOH terminus of unprocessed insulin-like growth factor 1, has no apparent effect on myoblasts or primary muscle stem cells. Am J Physiol Endocrinol Metab. 2014;306(2):E150-E156. [PMID 24253050, doi:10.1152/ajpendo.00408.2013]
- World Anti-Doping Agency. The 2026 Prohibited List — International Standard. Section S2: Peptide Hormones, Growth Factors, Related Substances and Mimetics (prohibited at all times). WADA; effective 1 January 2026. [wada-ama.org, wada-ama.org]