Follistatin
unknown riskAlso: FST · Follistatin-344 · FST-344
Follistatin is an endogenous glycoprotein that binds and inhibits myostatin (GDF-8) and activin — two potent inhibitors of muscle growth. Gene therapy with follistatin produces dramatic muscle hypertrophy in animal models. Not a peptide in the strict sense; included because it's grouped with muscle growth peptides.
Reported Benefits
Myostatin inhibition / muscle growth
Gene therapy (AAV-FST344) Phase I/II in muscular dystrophy shows significant muscle mass increases.
Mechanism of Action
Binds and neutralizes myostatin (GDF-8) and activins; removes brake on muscle hypertrophy; also suppresses FSH (fertility implications); promotes smooth muscle growth.
Key Clinical Studies
Mendell et al. (2015)
Open-label Phase I/II · n=6
Significant muscle mass increase in BMD patients with AAV-follistatin gene therapy
Gene Therapy, Not Injectable Peptide
Follistatin as a simple injectable peptide has poor pharmacokinetics. The clinically relevant administration is via AAV gene therapy — not the peptide itself. Claims of injectable follistatin effectiveness for bodybuilding extrapolate far beyond available evidence.
Muscular Dystrophy Application
Follistatin gene therapy has genuine clinical merit for Duchenne and Becker muscular dystrophy, where myostatin inhibition could preserve muscle function. This is the legitimate clinical development path.
Regulatory Status
Research OnlySafety Profile
Side Effects
- •Muscle hypertrophy without corresponding structural support
- •Reproductive effects (FSH suppression)
Contraindications
- •Hormone-sensitive conditions
- •Pregnancy
Primary Uses
Related Peptides
Weekly Briefing
Regulatory updates + new study breakdowns.
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