Follistatin Like Protein 4 (FSTL4)

FSTL4 encodes a protein with similarity to follistatin, an activin-binding protein. It contains an FS module, a follistatin-like sequence containing 10 conserved cysteine residues.

Follistatin is an autocrine glycoprotein that is expressed in nearly all tissues of higher animals.It was initially isolated from follicular fluid and was identified as a protein fraction that inhibited follicle-stimulating hormone (FSH) secretion from the anterior pituitary, and so was known as FSH-suppressing protein (FSP). Since then its primary function has been determined to be the binding and bioneutralization agent of members of the TGF-β superfamily, with primary focus on activin, a paracrine hormone (TGF-β member) which enhances secretion of FSH in the anterior pituitary.