Gsx disrupts the endocrine milieu, including that of circulating hormones regulating food intake and energy balance such as the orexigenic and pro-obesity hormone ghrelin (Ariyasu et al., 2001; Dornonville de la Cour et al., 2001) and also the anorexigenic hormones cholecystokinin (CCK; Inoue et al., 1987) and leptin (Furnes et al., 2008a). This evidence concerns the gene CCK and obesity due to melanocortin 4 receptor deficiency.