GDF9 and polycystic ovary syndrome: Reduced expression of BMP15 and GDF9 has been reported in ovaries of women with polycystic ovary syndrome (PCOS) (Teixeira Filho et al. 2002, Zhao et al. 2010, Wei et al. 2011, 2014), and these studies agree that this is directly related with the aberrant follicle development and infertility observed in these women; consistent with the arrest of follicle development and infertility observed in 9-week DM ovaries.