The expression of genes associated with the endometrial function (HOXA10, PAX6, ESR1, ESR2, and IGFBP1) and insulin signaling (GAB1, SLC2A4, and IRS1) was evaluated in the mid-proliferative endometrium of PCOS patients and women without the disease (Figure 1). Here, ESR2 is linked to polycystic ovary syndrome.