It was reported that serum RBP4 levels associated negatively with insulin sensitivity (determined by a hyperinsulinemic euglycemic clamp) in non-diabetic [5] or impaired glucose metabolism participants [6] and in women with polycystic ovary syndrome [7] or in women with normal glucose tolerance with different obesity [8]. The gene discussed is RBP4; the disease is obesity due to melanocortin 4 receptor deficiency.