LEP and rheumatoid arthritis: Serum leptin concentrations expressed in three ways were all significantly higher in patients with RA than those in controls [median 18.9 ng/mL (interquartile range: IQR 10.9–28.2 ng/mL) vs. 13.8 ng/mL (8.7–23.3 ng/mL), P = 0.021; 0.84 ng/mL/BMI (0.49–1.25 ng/mL/BMI) vs. 0.56 ng/mL/BMI (0.40–0.90 ng/mL/BMI), P = 0.002; 1.24 ng/mL/kg fat (0.82–1.72 ng/mL/kg fat) vs. 0.76 ng/mL/kg fat (0.54–1.23 ng/mL/kg fat), P < 0.001].