All peptides / Muscle and bone
Mechano growth factor
IGF-1 splice variant
Also MGF, MGF peptide, PEG-MGF, PEG MGF, IGF-1Ec, IGF-1 Ec
- Evidence
- CAnimal and cell studies
- FDA status
- Not approvedas of 2026-10-26
- Route
- Injection
- Studies cited
- 1 human2 animal or cell
It is sold as an injection to grow muscle and heal faster. No one has published a trial of it in people; the studies are in lab cells.
Sold for
Mechano growth factor is sold as a muscle-repair peptide that mimics what exercise does, promising faster hypertrophy and recovery after injury.
Studies say
Exercise raises MGF expression in young muscle and the E-domain peptide activates muscle stem cells in a dish, but no one has published a trial of injecting it into people, so the evidence is grade C.
Why grade C. The human evidence is a 2003 biopsy study in 15 volunteers showing that resistance exercise raises MGF gene expression in muscle, which says nothing about injecting the peptide. The rest is cell culture: a 2011 study of human muscle progenitor cells and a 2008 bacterial expression and osteoblast study. No human has received MGF in a published trial, so C. 234
FDA. Not approved by the FDA for any use. Mechano growth factor has never entered a registered clinical trial as a drug; it is sold online as a research chemical and used as a performance drug. 3
Written from 4 cited sources. Last refreshed 2026-10-27. Not physician reviewed.
What this means for you
- What people take it for
- Building muscle and recovering from injury
- Can a US doctor prescribe it?
- No. It is not approved and is sold as a research chemical.
- Properly tested in people?
- Not properly: lab cell studies and one biopsy study of 15 men, with none given the drug.
Evidence checklist
- Randomised controlled trial No trial of injected MGF in humansno
- Human study over 100 people Biopsy study of 15 men, no MGF givenno
- More than one research group A few cell and biopsy studies onlyno
- Clinical outcomes, not surrogate markers No clinical outcomes measuredno
- Human safety data beyond case reports No human safety datano
Drawn from the cited studies below. A dash means the sources give no information.
What it is
Mechano growth factor (MGF) is not a separate gene product. It is a splice variant of insulin-like growth factor 1, called IGF-1Ec in humans, produced when muscle is stretched or damaged. Alternative splicing gives it a different tail region (the E domain) from the liver form of IGF-1. The commercial product called MGF is usually a synthetic 24-amino-acid peptide copying that E domain, sometimes PEGylated to make it last longer. 34
The name comes from Geoffrey Goldspink's group in London, which showed in the late 1990s and 2000s that this splice form appears in muscle after mechanical loading. That work on the natural molecule is what vendors cite when selling the synthetic peptide, which has not been tested in people. 34
How it works
The proposed mechanism has two parts. The mature IGF-1 portion of the full splice variant acts through the IGF-1 receptor like any IGF-1. The E-domain peptide is claimed to act separately, through an unidentified receptor, to activate satellite cells, the muscle stem cells that fuse into damaged fibers to repair them. In cultured human muscle cells, the E peptide increased proliferation and delayed senescence in cells from young donors but not from old donors. 3
What human research shows
The only human study in the citations took muscle biopsies from eight young and seven older men 2.5 hours after a bout of heavy single-leg knee extension. MGF messenger RNA rose significantly in the young men but not in the older men, while the standard IGF-1Ea form did not change in either group. The study measured the body's own gene expression; no MGF was given. 4
There are no published trials, controlled or otherwise, of injected MGF in humans for muscle growth, recovery, or anything else. 34
| Study | Model | Finding |
|---|---|---|
| IGF-1 splice variants after resistance exercise (Hameed 2003) | Humans, n=15 (8 young, 7 older), muscle biopsy after exercise | Exercise raised MGF mRNA in young but not older muscle; no peptide was administered. 4 |
| MGF E-peptide on human muscle progenitor cells (Kandalla 2011) | Cell culture, primary human muscle cells of different donor ages | The E peptide increased proliferation and delayed senescence in cells from young donors, not old donors. 3 |
| Recombinant MGF expression and osteoblast assay (2008) | Cell culture, mouse MC3T3-E1 osteoblast-like cells | A bacterially produced E-domain fragment increased osteoblast proliferation and migration. 2 |
Safety
No human safety data exist. The theoretical concern follows from IGF-1 biology: IGF-1 signaling promotes cell growth, and the 2011 cell study itself framed the E peptide's appeal as avoiding the oncogenic side effects of IGF-1, a claim not tested in any organism. Products sold as MGF or PEG-MGF are unregulated, with no assurance of identity, purity, or sterility. 3
Questions for your clinician
- Has injected MGF ever been tested in a controlled human trial?
- What does IGF-1 signaling mean for my cancer risk?
- How could I know that a product labeled MGF or PEG-MGF is what it says?
Questions people ask
Is mechano growth factor FDA-approved?
No. It has no approval and no registered clinical trials. It is sold as a research chemical. 3
Has MGF been tested in humans?
Not as an injected drug. The one human study measured how exercise changes the body's own MGF gene expression in muscle biopsies from 15 men. 4
Does MGF build muscle?
In cell culture, the E-domain peptide activates muscle stem cells from young donors. Whether injecting it does anything in a living person has not been studied. 3
Citations
- Kandalla 2011, Mech Ageing Dev: MGF-E peptide activates human muscle progenitor cells (DOI record) doi.org
- 2008, Chin J Biotechnol: Expression of mechano-growth factor in E. coli and activity analysis pubmed.ncbi.nlm.nih.gov
- Kandalla 2011, Mech Ageing Dev: MGF-E peptide activates human muscle progenitor cells at different ages pubmed.ncbi.nlm.nih.gov
- Hameed 2003, J Physiol: IGF-I splice variants in young and old human muscle after resistance exercise pubmed.ncbi.nlm.nih.gov