Retinol binding protein (RBP) 4 is a vitamin A transport protein that acts as an adipokine when secreted from adipose tissue. Increased circulating RBP4 concentrations have been reported in several metabolic complications such as obesity, insulin resistance, metabolic syndrome, and cardiovascular disease. Increased expression of RBP4 positively correlates with increases in pro-inflammatory cytokines and LDL cholesterol in diet-induced obese and hyperlipidemic mice. Reduction of RBP4 has been shown to improve insulin resistance and dyslipidemia. This implicates RBP4 in regulating systemic insulin sensitivity and lipid metabolism, making measurement of serum or plasma RBP4 a useful means to monitor metabolic disorders and to possibly indicate cardiovascular disease risk. Cayman's RBP4 (human) Competitive EIA Kit is a competitive assay which can be used to measure RBP4 in human plasma, serum, urine, and cell culture supernatants.