Beyond its role as an orexigenic signal, ghrelin signaling has been recognized as a key regulator of obesity, insulin resistance and diabetes (Vijayakumar et al., 2011; Pradhan et al., 2013) and may involve in the pathological mechanisms of MetS (Langenberg et al., 2005). The gene discussed is GHRL; the disease is obesity due to melanocortin 4 receptor deficiency.