RBP4 and obesity due to melanocortin 4 receptor deficiency: The serum levels of other relevant adipokines, including leptin, retinol-binding protein-4 (RBP-4), resistin and visfatin, are known to increase with obesity.20 These adipokines are involved in different aspects of metabolism, such as regulating energy expenditure and food intake, stimulating insulin resistance through the impairment of insulin signaling in muscle, inducing the expression of hepatic gluconeogenic enzymes, regulating insulin secretion and evoking vascular and endothelial dysfunction.1, 20