Follistatin 344 vs 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 profileMGF
MGF (Mechano Growth Factor) is a splice variant of IGF-1 produced locally in muscle tissue in response to mechanical loading (exercise, especially eccentric loading). Unlike circulating IGF-1 which is produced primarily by the liver, MGF is generated within the muscle itself and acts locally to activate satellite cells (muscle stem cells) — the cells responsible for muscle repair, growth, and adaptation. It is considered the primary local anabolic signal generated by resistance training.
Full profile| Follistatin 344 | MGF | |
|---|---|---|
| Category | Performance & Growth Hormone | Performance & Growth Hormone |
| Also known as | FST-344, Follistatin isoform 344, FST | Mechano Growth Factor, IGF-1Ec, Insulin-like Growth Factor splice variant |
| Evidence | Research-stage | Preclinical only |
| Dosing range | 50mcg–200mcg mcg, Once daily or every other day for 10–30 day cycles | 100mcg–300mcg mcg, Post-workout (within 30–60 minutes of training), 3–4x weekly |
| Administration | Subcutaneous injection, Intramuscular injection (into target muscle — local effect hypothesis) | Intramuscular injection (into worked muscle — critical for local effect), Subcutaneous injection (produces more systemic distribution) |
| 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 | Localized muscle swelling at injection site (normal response), Hypoglycemia (less pronounced than IGF-1 DES but present), Very short half-life means side effects are brief, Potential overuse injury if post-workout injection is used consistently without adequate recovery |
| Cited sources | 3 references | 3 references |
Key differences
- Evidence level differs: Follistatin 344 is research-stage, while MGF is preclinical only.
- Administration: Follistatin 344 — Subcutaneous injection, Intramuscular injection (into target muscle — local effect hypothesis); MGF — Intramuscular injection (into worked muscle — critical for local effect), Subcutaneous injection (produces more systemic distribution).
- Frequency: Follistatin 344 is typically Once daily or every other day for 10–30 day cycles; MGF is Post-workout (within 30–60 minutes of training), 3–4x weekly.
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.
MGF
MGF is encoded by the IGF-1 gene but produced via alternative splicing that generates a unique 49-amino acid C-terminal E-peptide (Ec peptide). The Ec peptide has distinct biological activity from the IGF-1 domain — it directly activates satellite cell proliferation through a receptor pathway separate from the standard IGF-1R. Studies in rodents show that local MGF injection produces significant muscle hypertrophy in the injected limb without systemic IGF-1 elevation. MGF expression spikes within 30 minutes of resistance exercise and declines over 24–48 hours — aligning precisely with the post-exercise anabolic window.
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.