MSTN and polycystic ovary syndrome: Fang and colleagues (38) showed that, compared with women not suffering from PCOS, the serum GDF-8 concentration of PCOS patients was higher on GnRH-a day, Gn day, hCG day, 12 h after hCG administration, OPU day, 48 h after OPU and 14 days after ET.