Recently, DRD2 was identified as a gene contributing to PCOS development (polymorphisms in DRD2 may predispose individuals to the development of PCOS), and concomitantly, DRD2 was reported to increase the risk for type 2 diabetes and depression, both of which can coexist with PCOS [79, 80]. Here, DRD2 is linked to type 2 diabetes mellitus.