To confirm the activation of ER stress and the increased expression of TGF-β1 in granulosa cells of PCOS patients, immunohistochemical analysis was performed to examine the distribution of activated ER stress sensor proteins, inositol-requiring enzyme 1 (IRE1) and double-stranded RNA-activated protein kinase-like ER kinase (PERK), and CHOP, as well as TGF-β1, in the ovaries of PCOS patients. Here, ERN1 is linked to polycystic ovary syndrome.