PEG-MGF
PEGylated Mechano Growth Factor (IGF-1Ec C-terminal E peptide) · Pegylated MGF · MGF · IGF-1Ec · Mechano Growth Factor E peptide · MGF C-25E
PEGylated IGF-1Ec E-peptide used after training to extend satellite-cell signalling.
Typical dose
200 mcg
2x weekly
Range
100–400
mcg
Half-life
—
see Dosing
Evidence
Animal only
Subcutaneous · Intramuscular
What it is
Mechano growth factor is not a separate gene. It is a splice variant of IGF-1 produced by muscle after mechanical loading or damage, in which a frameshift in the E domain yields a distinct 24-amino-acid C-terminal peptide. That peptide, synthesised on its own, is what is sold as MGF.
Raw MGF is destroyed in circulation within minutes, which makes injectable use awkward. PEG-MGF attaches a polyethylene glycol chain (commonly around 5 kDa) to the peptide to slow renal clearance and proteolysis, which is why it is dosed twice weekly rather than daily.
The honest position: the E peptide has in vitro and rodent data suggesting satellite cell activation, and it is usually said to act through some target other than the IGF-1 receptor - but that receptor has never been identified, and the most careful replication attempt (Fornaro et al., Am J Physiol Endocrinol Metab 2014, PMID 24253050) found the synthetic MGF peptide had no apparent effect on myoblasts or primary muscle stem cells at all. The PEGylated version specifically has no published pharmacokinetics and no human trials at all. The half-life figures vendors quote are marketing, not measurement.
How it works
The MGF E peptide acts separately from mature IGF-1. Rather than binding the IGF-1 receptor, it appears to signal through a distinct, still incompletely characterised membrane target that pushes quiescent satellite cells into the cell cycle and delays their differentiation, expanding the pool of myonuclei available to fuse into damaged fibres. In cell culture, mature IGF-1 drives differentiation while the E peptide drives proliferation, and the two are complementary rather than redundant.
PEGylation does nothing to the mechanism. The PEG chain is inert bulk that increases hydrodynamic radius, slowing filtration by the kidney and shielding the peptide from peptidases so more of an injected dose survives long enough to reach tissue.
Dosing
Non-PEGylated MGF is a different protocol entirely: it is dosed immediately post-workout on training days because it is gone within minutes. Do not carry PEG-MGF's twice-weekly schedule over to plain MGF or vice versa.
Reconstitution calculator
Pre-loaded with PEG-MGF’s vial size, water volume and typical dose. Change anything.
Typical: 200 mcg · range 100–400
Draw to
20 u
0.2 mL · 200 mcg
Concentration
1 mg/mL
10 mcg per unit
Doses per vial
10
Vial lasts
5 weeks
Draw to 20 units on the barrel.
Once mixed
Refrigerate at 2-8C and use within 3-4 weeks; discard sooner if the solution clouds or the pellet fails to fully dissolve. This vial would take about 5 weeks to finish — check that against the storage window before mixing the whole thing.
2 mL of bacteriostatic water into a 2 mg vial gives 1000 mcg/mL, so a 200 mcg dose is 20 units on a U-100 insulin syringe. Run the water down the inside wall of the vial and swirl gently; PEGylated peptides foam readily and shaking will denature the peptide portion.
Storage
Before mixing
Stable 18-24 months at -20C, or several weeks in the fridge at 2-8C while in use.
After mixing
Refrigerate at 2-8C and use within 3-4 weeks; discard sooner if the solution clouds or the pellet fails to fully dissolve.
Reported benefits
- ▪Activates satellite cells and expands the myonuclear pool after training damage
- ▪Delays satellite cell differentiation, keeping more cells proliferating
- ▪PEG chain removes the need for daily or peri-workout-only dosing
- ▪Acts independently of the IGF-1 receptor, so it does not carry IGF-1's hypoglycaemic effect
- ▪No suppression of endogenous GH or IGF-1 production
- ▪Rodent data support a role in repair of damaged muscle and cardiac tissue
Side effects
- ▪Injection-site redness, itching or a persistent lump, more common with PEGylated peptides
- ▪Transient flushing or warmth after injection
- ▪Headache and lethargy reported anecdotally in the hours after dosing
- ▪Possible immune response to the PEG moiety itself; anti-PEG antibodies are documented for PEGylated drugs
- ▪No human safety data of any kind, so unknown long-term risk
- ▪Frequently misidentified or underdosed on the grey market, since PEGylation is hard to verify by eye
Do not use if
- ▪Active malignancy, given the compound's proliferative signalling
- ▪Known hypersensitivity to PEGylated drugs
- ▪Pregnancy and breastfeeding, with no data at all
- ▪Active systemic infection, where you do not want to add an unquantified proliferative stimulus
Evidence level — Animal only
Preclinical animal data — no meaningful human trials.
Not approved by any medicines regulator, sold as a research chemical, and prohibited in sport under the WADA code as a growth factor.
Commonly run with
IGF-1 DES
Truncated IGF-1 analogue with roughly 10x potency and a 20-30 minute window of action.
100 mcg · Once daily
IGF-1 LR3
Modified IGF-1 that evades its binding proteins, making it far more potent than the native hormone.
40 mcg · Once daily
HGH
Recombinant human growth hormone, the reference compound every GH peptide tries to imitate.
2 IU · Once daily, split into two injections above about 4 IU
BPC-157
Gastric-juice-derived pentadecapeptide studied for tendon, ligament and gut healing.
250 mcg · 1x daily (some split into 2x daily during an acute injury)
PEG-MGF FAQ
Is PEG-MGF better than plain MGF?+
It is more practical, not necessarily more effective. Plain MGF is cleared in minutes, so it only makes sense injected immediately post-workout; the PEG version survives long enough that twice-weekly dosing is workable. No head-to-head data exists in humans.
How long is the half-life really?+
Nobody has published a measured value for PEG-MGF. Unmodified MGF is gone in minutes, and a 5 kDa PEG chain typically extends peptide half-life by an order of magnitude or more, but the 48-72 hour figure on vendor pages has no measurement behind it.
Will it lower my blood sugar like IGF-1?+
No. The E peptide does not act on the IGF-1 receptor or cross-react meaningfully with the insulin receptor, so the hypoglycaemia seen with IGF-1 DES and LR3 is not part of this compound's profile.
Can it be injected into a specific muscle for local growth?+
People do it, but there is no human evidence that site injection produces localised hypertrophy. The rodent work involves direct intramuscular delivery, and even there the effect is on repair capacity rather than dramatic local size.
References
- 1.Different roles of the IGF-I Ec peptide (MGF) and mature IGF-I in myoblast proliferation and differentiation — FEBS Letters (2002) PMID 12095637
- 2.Muscle satellite (stem) cell activation during local tissue injury and repair — Journal of Anatomy (2003) PMID 12892408
- 3.Mechano Growth Factor E peptide (MGF-E), derived from an isoform of IGF-1, activates human muscle progenitor cells and induces an increase in their fusion potential at different ages — Mechanisms of Ageing and Development (2011) PMID 21354439
- 4.Mechano-growth factor peptide, the COOH terminus of unprocessed insulin-like growth factor 1, has no apparent effect on myoblasts or primary muscle stem cells — American Journal of Physiology-Endocrinology and Metabolism (2014) PMID 24253050
More growth factors
ACE-031
Myostatin and activin decoy receptor; human trials were halted over bleeding side effects.
1 mg · Once weekly
Follistatin 344
Activin- and myostatin-binding protein run in short daily courses; data are animal-only.
100 mcg · Once daily
IGF-1 DES
Truncated IGF-1 analogue with roughly 10x potency and a 20-30 minute window of action.
100 mcg · Once daily
IGF-1 LR3
Modified IGF-1 that evades its binding proteins, making it far more potent than the native hormone.
40 mcg · Once daily