PEG-MGF vs Follistatin 315
Side-by-side comparison of key properties, dosing, and research.
Anabolic & IGF
PEG-MGFAnabolic & IGF
Follistatin 315- Summary
- PEG-MGF (Pegylated Mechano Growth Factor) is a modified form of MGF (Mechano Growth Factor) where polyethylene glycol (PEG) chains have been attached to extend its half-life from minutes to days. Native MGF is released locally in muscle in response to mechanical stress and quickly degrades. PEGylation allows systemic administration with sustained circulation, enabling whole-body muscle repair and anabolic signaling rather than the purely local effect of native MGF.
- Follistatin 315 is a splice variant isoform of follistatin produced by alternative mRNA processing. Unlike Follistatin 344 which is tethered to cell surfaces via heparan sulfate proteoglycans, FST-315 circulates freely in the bloodstream and has broader systemic distribution. It is the predominant circulating form and exerts systemic myostatin inhibition as well as FSH suppression, making it relevant to both muscle growth and reproductive endocrinology.
- Half-Life
- ~3 days (due to PEGylation)
- ~3–5 hours (longer systemic circulation vs FST-344)
- Admin Route
- SubQ
- SubQ, IM
- Research
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- Typical Dose
- 200–400 mcg
- No established human dosing protocol
- Frequency
- 2–3x per week
- Research use only
- Key Benefits
- Extended half-life (~3 days) vs native MGF (minutes)
- Systemic muscle satellite cell activation via subcutaneous injection
- Promotes muscle fiber repair and hypertrophy throughout the body
- Enhanced recovery from intense training or muscle injury
- Synergistic with IGF-1 LR3 and growth hormone peptides
- Useful in sarcopenia, post-injury recovery, and athletic performance
- Single injection provides multi-day anabolic signaling
- Systemic myostatin inhibition for whole-body muscle growth
- Freely circulating — broader tissue distribution than FST-344
- Strong FSH-suppressive activity useful in certain hormonal protocols
- Potential for greater anabolic effect across multiple muscle groups simultaneously
- May be more relevant to reproductive endocrinology applications
- Studied in gene therapy approaches for muscular dystrophy
- Side Effects
- Water retention and localized swelling
- Potential hypoglycemia at high doses
- Theoretical cancer growth risk (growth factor)
- Injection site reactions
- +1 more
- Systemic FSH suppression — significant concern for fertility
- Greater potential for off-target effects vs FST-344 due to systemic distribution
- Limited human safety data
- Potential cardiac hypertrophy with prolonged high-dose exposure
- Stacks With
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