Body Composition · Musculoskeletal
Follistatin
Also known as: FS, ACE-083 (related construct), FST-344 (isoform), FST-315 (isoform)
An endogenous glycoprotein that binds and inhibits myostatin and activin, investigated in muscle-wasting conditions through both protein and gene therapy approaches.
Sign in to add to watchlistEvidence strength
Strength of human clinical evidence — A (strongest) to D (mostly preclinical). This reflects research maturity, not safety or suitability.
Vial Theory provides educational research summaries only. Content is not medical advice, diagnosis, treatment, dosing guidance, or individualized suitability screening. Regulatory status can change over time and varies by jurisdiction.
Key Takeaways
- ›Follistatin is a natural protein that blocks myostatin and activin, removing a brake on muscle growth.
- ›It has been investigated via gene therapy and protein approaches in muscular dystrophies and inclusion body myositis.
- ›Results show biological plausibility but modest, hard-to-translate functional benefits, and no broad approval.
- ›Related myostatin blockers have raised vascular and reproductive-axis safety concerns.
- ›Gray-market 'follistatin' rarely matches trial molecules. Speak with a licensed healthcare professional.
What It Is
Follistatin is an endogenous glycoprotein that functions as a high-affinity binding protein for several members of the TGF-beta superfamily, most notably myostatin (GDF-8) and activin A. By sequestering these ligands, follistatin prevents their binding to activin type II receptors, which removes a powerful inhibitory signal on muscle growth and contributes to broader regulation of inflammation, fibrosis, and reproductive biology.
Multiple follistatin isoforms exist in humans, including FST-315 (predominantly serum-circulating) and FST-288 (more tissue-bound). Therapeutic development has pursued several approaches: recombinant follistatin protein, fusion constructs (such as FST-Fc), myostatin-binding decoy receptors (ACE-031 and related ActRIIB-based therapeutics), and AAV-mediated gene therapy delivering follistatin to muscle. The 'follistatin' label in compounding-pharmacy and gray-market contexts is generally not specific about which form is sold and rarely matches the molecules used in formal trials.
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Disclaimer: This content is for educational and research purposes only and is not medical advice. Always consult a licensed healthcare professional before making health-related decisions.