Two things share one name
"MGF" means two different things, and most confusion about it comes from treating them as one.
The body's MGF is a version of IGF-1. The IGF-1 gene can be read in more than one way — biologists call this alternative splicing — and one reading, called IGF-1Ec in humans, rises in muscle after it is stretched, overloaded or injured. Geoffrey Goldspink's group in London found the equivalent form in rabbit muscle under stretch and published it in 1996 (Yang et al., PMID 8884603), naming it mechano growth factor for the stimulus that switched it on.
The sold MGF is a synthetic peptide of 24 amino acids, copied from the far end of that form. It does not contain IGF-1's 70-residue working core at all. PEG-MGF is the same 24-mer with a polyethylene glycol chain bolted on to slow its clearance.
Reading the sequence
UniProt files human IGF-1 as P05019 and lists four isoforms. Isoform 4 — the one whose tail matches — is a 158-residue precursor: a signal sequence, a short pro-region, the 70-residue IGF-1 chain, then a 40-residue E peptide. The E peptide's last 24 residues are:
YQPPSTNKNTKSQRRKGSTFEERK
That is the string sold as MGF. Matching it to isoform 4 is our reading of the UniProt record (2026-10-28); the published literature calls this form IGF-1Ec.
What the human studies actually measure
PubMed returns 194 records for "mechano growth factor" (2026-10-28). Five are tagged as randomised controlled trials. Every one of them measures the body's own MGF:
| Study | What changed | What was measured |
|---|---|---|
| Hameed 2004, J Physiol (PMID 14565994) | Growth hormone + resistance training, elderly men | IGF-1 isoform mRNA in muscle |
| Wilborn 2009, J Strength Cond Res (PMID 19826309) | Resistance-exercise intensity | Muscle growth regulators incl. MGF |
| Strasser 2009, Ann Surg (PMID 19387331) | Electrical muscle stimulation after abdominal surgery | Protein breakdown and IGFs |
| Delgado-Diaz 2011, Am J Sports Med (PMID 21785002) | Therapeutic ultrasound | IGF-1 splice variants |
| Popov 2015, Muscle Nerve (PMID 24916884) | Exercise intensity and metabolic stress | Anabolic signalling genes |
These show that exercise and other loading can turn up MGF production in human muscle. None gives anyone the synthetic peptide. It is a common slide in marketing to move from "your muscle makes MGF when you train" to "injecting MGF builds muscle"; the second claim has no published human test.
PubMed holds one record naming PEG-MGF: a 2026 narrative review from Poznan University of Medical Sciences (Dominikowski et al., Frontiers in Endocrinology, PMID 42395176). It groups PEG-MGF with IGF-1 LR3, the GHRH analogue CJC-1295 and AOD-9604 as GH–IGF-1 axis peptides used in online self-administration, sorts such peptides into evidence tiers down to "a complete absence of human studies", and flags hormonal and "biologically plausible but unproven mitogenic" concerns — growth signals do not choose which cells they reach. ClinicalTrials.gov lists no study of PEG-MGF.
Where it stands
Approved as a medicine: neither MGF nor PEG-MGF, anywhere.
In the body: a real, well-described splice form of IGF-1 that muscle makes under load.
As a sold peptide: a 24-residue fragment with cell and animal work behind it and no human trial.
For the training and recovery questions that usually lead here, MuscleLedger's MGF page covers the athlete's side. Anyone weighing growth-factor peptides for a health reason needs a doctor who can check IGF-1 and glucose.
Last checked
2026-10-28.