VDR and obesity due to melanocortin 4 receptor deficiency: As metabolic disorders have become much more prevalent recently [23], more genome-wide association and cohort studies were conducted and more variant genes and novel single nucleotide polymorphisms (SNPs) are found in large Chinese PCOS population [24,25], which have been confirmed later by multi-ethnic studies [26,27], including thyroid associated protein gene [28], Fat Mass and Obesity (FTO) gene [29,30], Follicle-stimulating Hormone Receptor (FSHR) gene [31,32], DENN/MADD domain containing 1A gene [33], Vitamin D Receptor (VDR) gene [34–36] and so on.