A sterol; an intermediate in cholesterol biosynthesis from lanosterol; found at high concentrations in mammalian ovarian follicular fluid; increases survival of human oocytes isolated from patients with PCOS; improves cytoplasmic maturation of immature rodent and porcine oocytes in vitro; promotes completion of meiotic maturation to metaphase II and increases the rate of successful IVF in isolated mouse oocytes,