Follistatin
FST · FS-344 · Follistatin 344 · Myostatin Inhibitor
The myostatin blocker that unlocks muscle growth potential — the 'Belgian Blue' gene in a vial.
What is Follistatin?
If you have ever seen photos of Belgian Blue cattle — those absurdly muscular cows that look like they bench press tractors — you have seen what happens when myostatin is inhibited. Myostatin is your body's brake pedal on muscle growth, and Follistatin is its natural antagonist. By binding and neutralising myostatin, Follistatin removes the ceiling on muscle protein synthesis. Your muscles can grow beyond their normal genetic set point.
Follistatin 344 is the full-length form of this naturally-occurring protein. Your body produces it endogenously, and levels increase after resistance exercise (this is part of how exercise stimulates muscle growth). Exogenous Follistatin administration aims to push myostatin inhibition beyond what your body achieves naturally — potentially unlocking dramatic muscle hypertrophy.
The reality is more nuanced than the hype. While animal studies and rare genetic cases (the famously muscular toddler with myostatin deletion) prove the concept, human data with exogenous Follistatin is limited. The delivery challenge is significant — it is a large protein that does not survive oral delivery and has a short half-life. Gene therapy approaches (AAV-Follistatin) have shown promise in muscular dystrophy trials, but injectable Follistatin peptide products have uncertain pharmacokinetics.
How Does It Work?
Follistatin binds directly to myostatin (GDF-8) and activin A, neutralising their biological activity. Without myostatin signalling:
1. Muscle satellite cells proliferate more readily. 2. Muscle protein synthesis ceiling is raised. 3. Muscle fibre hyperplasia (new fibre formation) may occur — not just hypertrophy. 4. Anti-catabolic effect — reduced muscle breakdown signalling.
Follistatin also binds activin A, which has additional effects on FSH (fertility), inflammation, and fibrosis. This broader activity profile means effects are not muscle-specific.
Delivery: FS-344 is a large protein (~35kDa). Subcutaneous injection provides systemic exposure but half-life is short. Gene therapy (AAV-FS) provides sustained expression.
What Does The Research Say?
Limited evidence. Mostly animal studies and anecdotal reports.
Gene therapy: AAV-Follistatin has completed human trials for muscular dystrophies (Becker, inclusion body myositis) with demonstrated safety and muscle volume increases. This is the most rigorous human data available.
Myostatin biology: Extensively validated. Myostatin-null animals across species show dramatic muscle hypertrophy. Human myostatin mutations produce extraordinary muscularity.
Injectable Follistatin: Very limited human data. Pharmacokinetics of injected protein are challenging — rapid clearance, potential immunogenicity. Most 'Follistatin' products from peptide suppliers are of uncertain bioactivity.
Exercise: Resistance training naturally increases Follistatin and decreases myostatin — this is one mechanism by which training promotes muscle growth.
Reported Dosages
These are dosages reported in research literature and community reports. They are NOT medical recommendations. Always consult a healthcare professional.
Injectable FS-344: Protocols vary widely — 100mcg daily subcutaneous is commonly discussed, but pharmacokinetic data to support this is essentially absent.
Some protocols suggest higher doses (100-200mcg) for short courses.
Bioavailability and actual in-vivo activity of injectable products is highly questionable.
DISCLAIMER: This is one of the most uncertain compounds in this database. The CONCEPT is validated (myostatin inhibition builds muscle) but whether injectable Follistatin products actually deliver meaningful myostatin inhibition in humans is genuinely unclear. Peptide quality concerns are significant. This is experimental in the truest sense.
Side Effects & Risks
Theoretical and observed (from genetic/gene therapy data): joint and tendon issues (muscle growth outpacing connective tissue adaptation), potential effects on reproductive hormones (Follistatin binds activin A, which regulates FSH), potential cardiac hypertrophy concerns (myostatin inhibition affects cardiac muscle too).
From injectable use: limited reports — mostly injection site reactions. Long-term safety of chronic myostatin inhibition is unknown. The body may have myostatin for good reasons beyond just limiting muscle size.
Legal Status by Country
Research peptide. Not approved for human use. Not specifically controlled.
Research chemical. Not FDA-approved. WADA-banned in sport.
Research peptide. Not approved as medication.
Not TGA-approved. WADA-banned. Research chemical.
Important Disclaimer
This profile is for educational and research purposes only. It does not constitute medical advice. Follistatin may be regulated or illegal in your jurisdiction. Do not use any compound without consulting a qualified healthcare professional. StackPedia does not sell, supply, or promote the use of any controlled substance.