INSR and obesity due to melanocortin 4 receptor deficiency: It is believed that multiple, instead of single genes, such as fibrillin-3 (FBN3), fat and obesity associated gene (FTO), insulin (INS), insulin receptor (INSR), insulin receptor substrate 1 (ISR1), DENN/MADD domain containing 1A (DENND1A), thyroid adenoma associated protein (THADA), and luteinizing hormone receptor (LHR), may contribute to the development of PCOS [7,8].