In ovarian cells, the expression of KLF4 and KLF13 mRNA is regulated by luteinizing hormone (LH) or/and insulin-like growth factor 1 (IGF1) in follicular granulosa cells (Natesampillai et al. 2008), while the dysregulation of KLF2 and KLF4 expression was noticed in polycystic ovary syndrome (PCOS) compared with the normal ovaries (Jansen et al. 2004). Here, KLF4 is linked to polycystic ovary syndrome.