INS and obesity due to melanocortin 4 receptor deficiency: The lack of insulin can be either due to an autoimmune dysfunction resulting in disruption of pancreatic beta-cells with a complete lack of insulin in diabetes mellitus type 1 (DM1) or due to insulin insensitivity in diabetes mellitus type 2 (DM2), most commonly in combination with the metabolic syndrome (obesity, dyslipidemia, hypertension and hyperglycemia).