Follistatin is a naturally occurring glycoprotein researched for its ability to inhibit myostatin and activin, potentially promoting significant muscle growth beyond natural limits. It exists in multiple isoforms (FST-288, FST-303, FST-315, FST-344) with different tissue distributions and binding properties.
Category: Growth & Performance. Evidence rating: C (early/mixed human evidence).
Clinical status: Preclinical and early clinical gene therapy trials for muscular dystrophies. Research compound for performance applications.
Binds to and neutralizes myostatin (a muscle growth inhibitor) and activin. By blocking these TGF-beta superfamily proteins, it may remove natural limits on muscle growth and promote hypertrophy. Also modulates FSH release through activin inhibition.
Safety considerations: Safety profile not well characterized for exogenous administration; Gene therapy trials showed acceptable safety in muscular dystrophy patients; Potential for reproductive effects due to activin/FSH pathway modulation.
Reviewed by the PeptideAtlas Editorial Team. Last reviewed: 2026-07-05.
FST-344 is the full precursor that gets cleaved to FST-315 (the predominant circulating form) and FST-303. FST-315 has a wider tissue distribution, while FST-288 is more tissue-bound. Most research products claim to be FST-344.
Yes, follistatin is a well-established natural myostatin inhibitor. However, exogenous administration effectiveness and the quality of grey-market products are questionable.
Follistatin is a naturally occurring glycoprotein researched for its ability to inhibit myostatin and activin, potentially promoting significant muscle growth. It is one of the most studied compounds for muscle development.
FOLLISTATIN has been studied for: Muscle growth promotion, Myostatin inhibition, Strength enhancement, Body composition improvement. Powerful myostatin inhibitor; significant research interest for muscle wasting conditions.
Binds to and neutralizes myostatin (a muscle growth inhibitor) and activin. By blocking these proteins, it may remove natural limits on muscle growth and development.