Follistatin

Research dosing is poorly standardized for exogenous follistatin peptide. Animal studies have used 0.75 mg/kg intraperitoneally twice daily, with dose-range studies testing 1-10 mg/kg every other day. Research-grade vials are commonly sold as 1 mg lyophilized powder. Follistatin 344 (FST-344) and Follistatin 315 (FST-315) are the same protein at different processing stages. Human dosage data is extremely limited; this peptide is restricted to licensed research use.

Binds activin in the extracellular space, blocking its type II receptor-binding site and inhibiting downstream Smad-dependent signaling. This is the primary mechanism of action.

Binds and neutralizes myostatin (GDF-8), a negative regulator of muscle growth, thereby removing the brake on muscle protein synthesis and hypertrophy.

By neutralizing activin, follistatin indirectly suppresses follicle-stimulating hormone (FSH) secretion from the pituitary.

Broadly binds and bioneutralizes multiple members of the TGF-beta superfamily beyond activin and myostatin, modulating cell differentiation and proliferation.

By inhibiting myostatin, follistatin removes a key negative regulator of skeletal muscle mass. Animal studies show significant increases in muscle fiber size and number.

Transgenic animal models expressing follistatin showed reduced fat deposition and improved metabolic profiles alongside increased muscle growth.

Improved metabolic profiles observed in animal models with elevated follistatin, including better glucose handling and energy expenditure.

Regulation of FSH levels through activin neutralization, influencing reproductive function.

Study 41750266

Study 41740294

Study 41738163