SLC2A4 and polycystic ovary syndrome: Another recent study observed that metformin improved the endometrial function of patients with Polycystic Ovarian Syndrome (PCOS) by modulating the DNA methylation of the gene promoter of HOXA10 and the expression of genes implicated in insulin signaling such as SLC2A4 and endometrial receptivity such as GAB1 [16].