What is it?
Follistatin is a naturally occurring human peptide and a potent inhibitor of myostatin. Myostatin encourages the degradation of myotubes (skeletal muscle fibers), and therefore inhibition of myostatin will ultimately result in increased muscle mass by preventing degradation. It is an autocrine glycoprotein that is expressed in nearly all tissues of higher animals. An earlier name for the same protein was SH-suppressing protein.
How does it work?
Follistatin binds directly to activin and functions as an activin antagonist. Activin is one of two dimeric proteins: it is a placental hormone that reaches maximum levels in maternal serum during labor or a nonsteroidal regulator synthesized in the pituitary glands that stimulates the secretion of follicle-stimulating hormone.
It is secreted protein that binds to ligands of the TGF-beta family and regulates their activity by inhibiting their access to signaling receptors. Follistatin is expressed in the pituitary, ovaries, decidual cells of the endometrium, and in some other tissues.
It prevents the breakdown of muscle tissue, which allows adipose, or fat, tissue to be more selectively targeted for energy reserves. This causes an increase in lean muscle mass and a decrease in fat tissue. Overall, this creates a very attractive combination for changing body composition. It must be used sparingly, so that tendons and ligaments have time to adjust.
In the blood, Follistatin and activin are both known to be involved in the inflammatory response following tissue injury or pathogenic incursion. It is also being studied for its role in regulation of muscle growth, as an antagonist to myostatin, which inhibits excessive muscle growth. Myostatin is a protein that acts on myocytes cells autocrine function to inhibit muscle cell growth and differentiation.
It must be used sparingly, so that tendons and ligaments have time to adjust to more muscle strain and stress. Injection site irritations has been reported by some and soreness at or near the injection site is normal.