LEP and obesity due to melanocortin 4 receptor deficiency: Impaired hypothalamic regulation of energy balance is found in numerous genetic forms of human obesity, including congenital deficiency of leptin (MIM 164160) [9], leptin receptor mutations (MIM 601007) [10], MC4R melanocortin receptor mutations (MIM 601665) [11], and Bardet-Biedl Syndrome (MIM 209900) [12].