VialOwlLibrary / Growth hormone
PEG-MGF
Also known as Pegylated mechano growth factor, MGF, IGF-1Ec
Animal studies only
Pegylated form of a splice variant of insulin-like growth factor 1 produced in muscle. Studied in cell and animal models only; FDA noted no human exposure data.
Not an approved medicine. PEG-MGF is not an approved medicine for this use in Australia or the United States. This page summarises published research for information only. It is not a recommendation to use PEG-MGF, and VialOwl does not sell or supply it.
Background
Mechano growth factor (MGF) is the name given in the 1990s by Geoffrey Goldspink's group in London to a splice variant of the IGF-1 gene (IGF-1Ec in humans) that rises in muscle after stretch or damage. The synthetic MGF sold today is a 24 amino acid tail peptide from that variant; PEG-MGF has polyethylene glycol attached to make it last longer.
How it is thought to work
Early lab studies claimed the MGF tail peptide activates muscle stem cells and delays their fusion, separately from mature IGF-1. Later independent testing by two drug companies could not reproduce these effects, and no natural MGF peptide has been isolated from tissue.
What is claimed, and the evidence
| Claim | Evidence | Notes |
|---|---|---|
| Muscle repair and growth after exercise or injury | Animal studies only | Early cell and animal studies; a 2014 independent study found no effect of MGF peptide on human or mouse muscle cells. |
| Cartilage and bone repair | Animal studies only | Cell and animal studies only; its role is described as still controversial. |
| Bodybuilding muscle gain and fat loss | No published evidence | Popular performance claims; no human studies of any kind. |
Side effects
| Effect | How often | Notes |
|---|---|---|
| Any human side effects | Frequency unknown | FDA identified no human exposure data on PEG-MGF by any route. |
| Low blood sugar, fluid retention, joint pain | Frequency unknown | Described generally for IGF-1 axis peptides in a 2026 review; not measured for PEG-MGF. |
| Theoretical cancer growth concern Serious | Frequency unknown | IGF-1 related peptides carry a biologically plausible but unproven mitogenic concern. |
| Immune reactions to the product Serious | Frequency unknown | FDA flagged a significant immunogenicity risk and peptide impurity concerns. |
Warnings
- FDA has found no human exposure data for PEG-MGF and does not know whether it would cause harm.
- Independent lab testing has questioned whether the MGF peptide has any biological effect at all.
- Unapproved products are not assessed by the TGA for quality, safety or efficacy and may be contaminated, non-sterile, underdosed, overdosed or contain a different substance altogether.
Regulatory status
- Australia
- Not included on the ARTG (unapproved). Likely captured by the Schedule 4 insulin-like growth factor class entry (Not verified).
- United States
- Not FDA approved. PEG-MGF nomination withdrawn and removed from 503A Category 2 in April 2026; MGF is in 503A Category 3.
Sources
- PubMed: Mechano-growth factor peptide has no apparent effect on myoblasts or primary muscle stem cells
- PubMed: Minireview: Mechano-growth factor: a putative product of IGF-I gene expression
- PubMed: The role of mechano growth factor in chondrocytes and cartilage defects: a concise review
- FDA: Certain bulk drug substances for use in compounding that may present significant safety risks (updated 22 April 2026)
Also in Growth hormone
From the VialOwl library, reviewed 26 September 2026. For education and general information. It is not medical advice and not a recommendation to use PEG-MGF.