MC4R and obesity disorder: MC4R deficiency in rodents and humans (Fan et al., 2000, Farooqi et al., 2003) is characterized by low blood pressure (BP; for the degree of obesity) due to impaired sympathetic nervous system activation (Greenfield et al., 2009, Sayk et al., 2010, Simonds et al., 2014, Tallam et al., 2005).