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). This evidence concerns the gene ESR1 and polycystic ovary syndrome.