MC4R and obesity due to melanocortin 4 receptor deficiency: Other genes associated with obesity have since been reported, including the melanocortin-4 receptor (MC4R) [5], adiponectin, C1Q and collagen domain containing [6], brain-derived neurotrophic factor [7], leptin [8], peroxisome proliferator-activated receptor gamma-2 [9] and SH2B1 genes [10].