Follistatin is a follicle-stimulating hormone (FSH) inhibiting substance which was first mentioned in 1987 [Phillips et al., 1998]. In addition, follistatin is expressed around the developing muscle [Amthor et al., 2004]. Follistatin was originally isolated from the follicular fluid of ovary in which this action inhibited the secretion of FSH [Chen et al., 2014]. In addition to its role as an activin-binding protein, it is considered an autocrine glycoprotein which is expressed in almost all tissues.
How it works
Follistatin is known as a single-chain glycoprotein in which its molecular weight can vary between 31 and 49 kDa [Krester et al., 2002]. Based on what happens once Follistatin is encoded by a cell’s machinery, two versions of follistatin appear: follistatin 315, and follistatin 288 [Krester et al., 2002] (the numbers indicate the number of amino acids in that particular sequence). Follistatin binds and neutralizes activin, in addition to this follistatin is involved in binding of other proteins that influence the bioavailability of other growth factors [Keutmann et al., 2004]. Moreover, follistatin is known as an antagonist of myostatin and activin A [Sepulveda et al., 2015].