IRS1 and polycystic ovary syndrome: In a few cases, genome variation in susceptible genes such as cytochrome P1A1, CYP17A1, (CYP1A1), CYP11A, CYP19, 17β-hydroxysteroid dehydrogenase (HSD17B6), androgen receptor (AR), insulin receptor (INSR), sex hormone-binding globulin (SHBG), insulin receptor substrate 1 (IRS1) and peroxisome proliferator-activated receptor gamma (PPAR-γ) [17] is responsible for PCOS.