NKX2-2 and obesity due to melanocortin 4 receptor deficiency: Regarding obesity, its pathogenesis may be linked to higher levels of ghrelin, an orexigenic hormone, most likely subsequent to the change of pancreatic islet cell differentiation, due to the absent NKX2.2 function, in favor of ghrelin-producing cells rather than the α-, β-, and PP cells [29,31].