Mechano growth factor (MGF) is a splice variant of the IGF-1 gene that muscle produces after stretch or overload; in humans it is called IGF-1Ec.
Geoffrey Goldspink’s group in London cloned the isoform from stretched rabbit muscle in 1996 and detected the human equivalent, IGF-1Ec, in muscle after altered physical activity (Yang et al., 1996). A 1999 follow-up named it mechano growth factor and described it as built for local action within muscle rather than circulation through the bloodstream (McKoy et al., 1999).
The evidence is laboratory and animal work only. A synthetic 24-amino-acid peptide from MGF’s E domain improved engraftment of human muscle precursor cells in mice and appeared to act through a route other than the IGF-1 receptor (Mills et al., 2007). A 2026 review in Frontiers in Endocrinology found no peer-reviewed human studies of MGF or its pegylated form, PEG-MGF, and noted a theoretical proliferative concern because MGF is expressed in some cancer tissue.
MGF is not FDA-approved for any use, and WADA lists mechano growth factors by name as banned at all times under class S2.3.
The 2026 WADA Prohibited List includes “mechano growth factors (MGFs)” among the growth factors in section S2.3, prohibited in and out of competition. The FDA’s compounding safety-risk page, current as of April 22, 2026, lists PEG-MGF among withdrawn compounding nominations and states that the agency has not identified any human exposure data on drug products containing it.
A product labeled MGF can mean the short E-domain peptide or the pegylated form, and pegylation changes the molecule’s mass a great deal. A credible result names which molecule was found and how much, so the label can be checked against what is in the vial.
Before trusting a label, check that batch’s published result on our latest tests page or in Janoshik’s public results database. No results are published for MGF in our index yet. When the first published result arrives, a vendor leaderboard appears above.