Follistatin

Follistatin (FST) is a naturally occurring protein that regulates cell growth and differentiation by binding and inhibiting members of the TGF-β superfamily, particularly activin and myostatin, leading to increased muscle mass, FSH suppression, and roles in development. It's crucial for embryonic muscle development, where it promotes muscle growth by blocking myostatin, a muscle growth inhibitor. Due to its muscle-enhancing effects, it's a banned substance in sports, but research explores its potential for treating muscle wasting diseases like Becker muscular dystrophy.