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Growth Hormone Axis

PEG-MGF

Pegylated fragment of the IGF-1 variant muscle makes after loading; preclinical only, with unresolved questions about whether it works.

RestrictedEvidence level 1 of 5: Preclinical / anecdotalAlso: Pegylated Mechano Growth Factor, PEG-IGF-1Ec E-peptide, Mechano Growth Factor, Pegylated

Overview

Mechano growth factor (MGF) is a splice variant of IGF-1 that muscle produces after mechanical loading or injury. The research peptide is a synthetic fragment of MGF's unique E-domain, and PEG-MGF attaches polyethylene glycol to extend its half-life from minutes to roughly a day or more. Early laboratory work suggested it activates muscle stem (satellite) cells and supports repair, which led to its use after training or injury. However, the evidence is entirely preclinical, several groups have failed to reproduce key findings, and there are no human studies. Because it belongs to the IGF-1 family, it is avoided in anyone with a cancer history.

Classification
PEGylated synthetic peptide derived from the E-domain of the IGF-1Ec (MGF) splice variant
Route
Subcutaneous or intramuscular
Half-life
Native MGF: minutes; PEG form: ~24–48 hours (estimated)

Mechanism of action

Primary targetSatellite cells via IGF-1Ec E-peptide signaling (receptor not fully defined)
  1. Released after loadingNative MGF rises in muscle after mechanical stress or damage.
  2. PEG extends exposurePegylation slows clearance, allowing intermittent dosing.
  3. Satellite cell activationProposed to wake quiescent Pax7-positive muscle stem cells.
  4. Myoblast proliferationExpands the pool of muscle precursor cells before differentiation.
  5. Fiber repairPrecursors fuse with damaged fibers, supporting repair and remodeling.
Downstream effects
  • Muscle repair (preclinical)
  • Satellite cell activity
  • Recovery support (theoretical)

Researched for

  • Muscle repair after injury (preclinical)
  • Age-related muscle loss (in vitro)
  • Cardiac protection after infarction (animal)
  • Hypertrophy with resistance training

Research notes

  • Human muscle biopsies (Hill & Goldspink 2003) show the IGF-1Ec splice variant rises after loading — endogenous MGF, not the drug.
  • Cell studies (Kandalla 2011) reported improved function of aged human muscle precursor cells.
  • Independent groups (e.g., Fornaro 2014) found no myogenic effect of the synthetic E-peptide, questioning the mechanism.
  • No human pharmacokinetic, efficacy or safety studies of PEG-MGF exist.

Reported side effects

  • Injection-site soreness or lumps
  • Mild hypoglycemia (possible)
  • Fatigue
  • Unknown long-term effects

Contraindications & cautions

  • Current or prior malignancy
  • Pregnancy or breastfeeding
  • Untreated proliferative retinopathy
  • Severe cardiac disease (caution)

Lab monitoring

  • IGF-1
  • Fasting glucose and HbA1c
  • CBC and CMP
  • Lipid panel
  • Age-appropriate cancer screening

Dosing and pricing for PEG-MGF

Dosing references and compound pricing are available to established patients in the secure portal after a medical evaluation.

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