This MAb reacts with a protein of 22kDa, identified as a beta subunit of FSH. It does not cross-react with the alpha subunit. Follicle stimulating hormone (FSH) is a hormone synthesized and secreted by gonadotrophs in the anterior pituitary gland. In the ovary, FSH stimulates the growth of immature Graafian follicles to maturation. As the follicle grows, it releases inhibin, which deactivates the FSH production. In men, FSH enhances the production of androgen-binding protein by the Sertoli cells of the testis and is critical for spermatogenesis. FSH and LH act synergistically in reproduction. FSH is a useful marker in the classification of pituitary tumors and the study of pituitary disease.