Follistatin 344 vs PEG-MGF
A neutral, side-by-side comparison of two performance & growth hormone peptides — their mechanisms, dosing ranges, administration routes, side effects, and research evidence. For research and educational purposes only.
Follistatin 344
Follistatin 344 is a 344-amino acid isoform of follistatin — an endogenous glycoprotein that functions primarily as a myostatin and activin inhibitor. Myostatin (GDF-8) is the body's primary muscle growth suppressor; follistatin binds and neutralizes it with high affinity, removing this brake on muscle protein synthesis. Research and animal data show dramatic increases in muscle fiber size and strength when follistatin is elevated or myostatin is inhibited.
Full profilePEG-MGF
PEG-MGF is Mechano Growth Factor (MGF) conjugated to a polyethylene glycol (PEG) polymer chain. The PEGylation dramatically extends the half-life from ~5 minutes (native MGF) to approximately 24–72 hours, allowing less frequent dosing and systemic distribution rather than purely local action. This trade-off — longer duration vs localized intensity — makes PEG-MGF a different tool than native MGF, better suited for systemic muscle recovery support and convenience-focused protocols.
Full profile| Follistatin 344 | PEG-MGF | |
|---|---|---|
| Category | Performance & Growth Hormone | Performance & Growth Hormone |
| Also known as | FST-344, Follistatin isoform 344, FST | PEGylated Mechano Growth Factor, Polyethylene Glycol-MGF, Long-acting MGF |
| Evidence | Research-stage | Preclinical only |
| Dosing range | 50mcg–200mcg mcg, Once daily or every other day for 10–30 day cycles | 100mcg–400mcg mcg, 2x weekly (Monday/Thursday or similar split) |
| Administration | Subcutaneous injection, Intramuscular injection (into target muscle — local effect hypothesis) | Subcutaneous injection (preferred for systemic distribution), Intramuscular injection |
| Key side effects | Potential FSH suppression (reproductive effects in females — may affect menstrual cycle), Accelerated hair follicle cycling (Wnt pathway involvement — theoretical hair loss concern at high doses), Joint discomfort with rapid muscle tissue growth, Limited long-term human safety data | Hypoglycemia (less pronounced than IGF-1 DES, more than native MGF due to systemic distribution), Generalized fatigue on injection days, PEG accumulation concern with very high doses over long periods (theoretical — not established at research doses), Localized injection site swelling |
| Cited sources | 3 references | 2 references |
Key differences
- Evidence level differs: Follistatin 344 is research-stage, while PEG-MGF is preclinical only.
- Administration: Follistatin 344 — Subcutaneous injection, Intramuscular injection (into target muscle — local effect hypothesis); PEG-MGF — Subcutaneous injection (preferred for systemic distribution), Intramuscular injection.
- Frequency: Follistatin 344 is typically Once daily or every other day for 10–30 day cycles; PEG-MGF is 2x weekly (Monday/Thursday or similar split).
- Research depth: this profile cites 3 sources for Follistatin 344 vs 2 for PEG-MGF.
How each works
Follistatin 344
Follistatin's muscle effects were dramatically illustrated when mice and cattle with follistatin overexpression or myostatin knockouts developed 2–3x normal muscle mass. Human follistatin gene therapy trials (AAV-mediated) are ongoing for Becker Muscular Dystrophy, showing sustained myostatin inhibition and improved muscle function over years from a single injection. Follistatin also inhibits activin A and B (involved in muscle wasting during illness), FSH secretion (reproductive effects), and inflammatory cytokines. The 344 isoform has an extended heparin-binding domain that increases tissue retention compared to the shorter FST-288 isoform.
PEG-MGF
PEGylation is a validated pharmaceutical strategy for extending peptide half-life (used in Pegasys/interferon, Somavert/pegvisomant, and others). The PEG chain shields the MGF peptide from proteolytic degradation and slows renal clearance. Research in rodent models confirms PEG-MGF preserves the biological activity of native MGF (satellite cell activation, muscle repair) with extended duration. Unlike native MGF which requires precise post-workout injection timing, PEG-MGF can be injected on a scheduled basis and still achieves systemic muscle-wide satellite cell effects.
This comparison aggregates public research and structured profile data for informational purposes only. It is not medical advice and does not recommend either compound for human use. Consult a qualified healthcare provider before considering any peptide.