PEG-MGF
MGF (mechano growth factor) is not a separate molecule the body makes on purpose. It is a name given to an alternative splice variant of the IGF-1 gene, IGF-1Ec in humans and IGF-1Eb in rodents, whose expression in skeletal muscle rises after mechanical loading and local tissue damage. Hill and Goldspink, publishing in the Journal of Physiology in 2003, showed that this splicing shift in rodent muscle tracked with satellite (stem) cell activation after local injury, which is the observation the entire MGF field is built on. Goldspink laid out the broader framing in Physiology in 2005: mechanical signals change how the IGF-1 gene is spliced, and the muscle adapts accordingly.
- class
- synthetic C-terminal E-domain peptide of IGF-1Ec, 24 amino acids, about 2.9 kDa before PEGylation
- modification
- polyethylene glycol chain attached to slow renal clearance and proteolysis
- route
- subcutaneous, sites rotated
- typical dose
- 200–400 mcg per injection, 2–3× weekly in self-directed protocols (no clinical dosing standard exists)
- half-life
- unmeasured for the PEGylated form; the 48–72 hour figure is a vendor claim, not a published PK result (see FAQ)
- storage
- lyophilized refrigerated 2–8°C; reconstituted with BAC water, 2–8°C, 28-day max
- regulatory
- research chemical, not approved for human use, WADA prohibited (S2 growth factors)
PEG-MGF Reconstitution & Dosage Protocol
weekly dose · reduces side effects| Phase | Window | Weekly dose | Draw (U-100, 2mL BAC) | Note |
|---|---|---|---|---|
| Reconstitution + baseline | Day 0 | 0.00 mg | 0 units· 0.00 mL | Reconstitute 2 mg in 2 mL bacteriostatic water for 1000 mcg/mL. At that concentration 200 mcg is 0.2 mL (20 units on a U-100 syringe) and 400 mcg is 0.4 mL (40 units), both well inside the range where a U-100 barrel measures accurately. Add the water slowly down the vial wall and swirl rather than shake: PEGylated peptides foam readily, and foaming is a sign of protein denaturation at the air/liquid interface. Log baseline strength numbers and bodyweight, because the effect this compound is claimed to produce is not something you can feel acutely |
| Opening block | Days 1–14 | 0.20 mg | 20 units· 0.20 mL | 200 mcg on non-consecutive training days, typically 3× weekly (20 units at 1000 mcg/mL). Post-workout is the conventional timing, on the reasoning that native MGF expression in muscle rises after mechanical loading. Unlike IGF-1 LR3, PEG-MGF has no meaningful insulin receptor cross-reactivity, so there is no hypoglycemia risk driving the timing and no requirement to dose with food |
| Standard block | Days 15–28 | 0.40 mg | 40 units· 0.40 mL | 400 mcg on the same 2–3× weekly cadence, the upper end of what appears in self-directed protocols. Doses beyond 400 mcg per injection have no supporting data of any kind, and given that the E-peptide bioactivity question is itself unresolved, raising the dose is not a way to resolve it |
| Washout | Days 29–56 | 0.00 mg | 0 units· 0.00 mL | Four weeks off. There is no receptor desensitization literature for MGF to justify a specific on/off ratio, so this mirrors the general convention applied to growth factor peptides rather than anything measured. Use the break to compare strength and bodyweight logs against the Day 0 baseline |
| Reassess | After week 8 | 0.00 mg | 0 units· 0.00 mL | Judge from the training log, not from pump or soreness. If nothing moved beyond what the training block alone would explain, the most likely reading is the one Fornaro and colleagues reported in 2014: the synthetic E-peptide had no apparent effect on myoblasts or primary muscle stem cells. Anyone with an active or historical malignancy should not restart, since the entire proposed mechanism is stimulation of progenitor cell proliferation |
What is PEG-MGF?
MGF (mechano growth factor) is not a separate molecule the body makes on purpose. It is a name given to an alternative splice variant of the IGF-1 gene, IGF-1Ec in humans and IGF-1Eb in rodents, whose expression in skeletal muscle rises after mechanical loading and local tissue damage. Hill and Goldspink, publishing in the Journal of Physiology in 2003, showed that this splicing shift in rodent muscle tracked with satellite (stem) cell activation after local injury, which is the observation the entire MGF field is built on. Goldspink laid out the broader framing in Physiology in 2005: mechanical signals change how the IGF-1 gene is spliced, and the muscle adapts accordingly.
The peptide sold as MGF is not that splice variant. It is a synthetic 24 amino acid fragment corresponding to the C-terminal E-domain of IGF-1Ec, roughly 2.9 kDa, on the hypothesis that this E-peptide is cleaved off in vivo and acts on its own, separately from the mature IGF-1 portion. PEG-MGF adds a polyethylene glycol chain to that fragment. PEGylation is a standard and well-understood technique for slowing renal filtration and proteolytic degradation of small peptides, and the unmodified MGF peptide clears from serum in minutes, so the rationale for attaching a PEG group is sound in principle.
The evidence for the E-peptide acting on its own is genuinely split, and this is the single most important thing to understand before spending money on it. On the supporting side, Ates and colleagues (FEBS Lett, 2007) reported that the MGF splice variant increased progenitor cell numbers in ALS, dystrophic, and normal muscle, and Kandalla and colleagues (Mech Ageing Dev, 2011) found the MGF-E peptide activated human muscle progenitor cells and raised their fusion potential across age groups. Dłużniewska and colleagues (FASEB J, 2005) separately reported a strong neuroprotective effect for the autonomous C-terminal peptide in a brain ischemia model, which is where the occasional neuroprotection claim comes from.
On the other side, Matheny, Nindl, and Adamo published a minireview in Endocrinology in 2010 whose framing is captured in its own title: MGF is a putative product of IGF-1 gene expression. Their point was that direct evidence for the E-peptide existing as a cleaved, circulating, bioactive entity in vivo was thin. Fornaro and colleagues then tested it directly in the American Journal of Physiology (Endocrinology and Metabolism) in 2014 and found that the synthetic MGF peptide had no apparent effect on myoblasts or primary muscle stem cells. That is a null result on the exact molecule vendors sell, in the exact cell types it is supposed to act on, and no subsequent work has overturned it.
There is no human clinical program for MGF or PEG-MGF, no published pharmacokinetic study of the PEGylated form, and no approved indication. What that means practically: the half-life figures quoted on vendor sites are not measurements, the dosing conventions are inherited from forum practice rather than from dose-finding work, and the local injection claim (that injecting a specific muscle produces growth in that muscle) is undercut by PEGylation itself, since the entire purpose of adding a PEG chain is to keep the peptide in systemic circulation longer. It is prohibited in sport under WADA class S2 as a growth factor. Anyone with an active or historical malignancy should treat the proposed mechanism, progenitor cell proliferation, as a reason to avoid it entirely.