RBP4 and obesity disorder: RBP4 levels were the highest in the subjects with both obesity and the low estrogen level (37.08 ± 7.29 μg/ml vs. 26.77 ± 3.47 μg/ml, 29.64 ± 7.8 μg/ml, and 30.9 ± 7.18 μg/ml, P for trend <0.001, respectively), compare to those with neither obesity nor low estrogen levels, individuals with no-obese but low estrogen levels, and individuals with obesity but high estrogen levels.