MC4R and obesity due to melanocortin 4 receptor deficiency: Xia et al. [12,13] reported obesity and T2DM shared a common genetic basis to PCOS through serval loci (ERBB3, FTO, PROX1, GIPR, and MC4R for obesity [12], and ADCY5, FTO, GIPR, and PPARG for T2DM [13]).