MC3R and Obesity: MC2R is required for adrenocortical steroidogenesis in the adrenal gland, and melanocortin-3 receptor (MC3R) and MC4R are essential for appetite control and energy homeostasis in the central nervous system.Mutations of MC4R have been reported as the most prevalent forms of monogenic obesity in humans, and the physiological roles of MC4R in regulating energy balance are well known and widely reported (4, 5).