MC4R and obesity due to melanocortin 4 receptor deficiency: Similar to the FTO gene, the MC4R gene is also highly expressed in the central nervous system, which regulates the energy metabolism.[19] It was reported that MC4R may regulate food choice and intake, and energy expenditure through a distinct pathway.[20,21] However, further studies are needed to clarify the potential biological pathways through which these MC4R SNPs increase the risk of obesity and cancer.