Fibroblast growth factor 21 (FGF21) belongs to a subfamily of the FGFs that function as the endocrine,which exerts wide-range effects on carbohydrate and lipid metabolism[1].For instance, FGF21-overexpressing mice were protected from diet-induced obesity, and therapeutic administration of FGF21 improved plasma glucose and triglyceride concentrations both in ob/ob and db/db mice[2]. The gene discussed is FGF21; the disease is obesity due to melanocortin 4 receptor deficiency.