To test whether there was a difference in serum retinol-binding protein 4 (RBP4) levels between subjects with polycystic ovary syndrome (PCOS) and those with a healthy regular menstrual cycle and, in addition, to correlate serum RBP4 levels with a variety of parameters.
A total of 74 nonobese women were evaluated. Thirty-seven had PCOS, whereas the remaining 37 served as control subjects.
Serum RBP4 levels were analyzed using ELISA.
Serum levels of FSH, LH, TSH, E(2), T, insulin, glucose, cholesterol, triglycerides, and RBP4.
The women with PCOS had higher levels of serum RBP4, waist-to-hip ratio, LH, T, insulin, homeostatic model assessment of insulin resistance, cholesterol, and triglycerides. Logistic regression analyses revealed a significant association between odds ratio (OR) values of PCOS and both T (OR = 1.125; 95% confidence interval [CI] 1.050-1.205), and cholesterol levels (OR = 1.029; 95% CI 1.004-1.056). Age and triglycerides were significantly correlated to serum RBP4 levels by multiple linear regression analysis.
Our study has shown that  elevated RBP4 levels might arise from triglyceride metabolism, and that RBP4 levels might not be influenced by PCOS itself.  RBP4 might not be a useful marker of insulin resistance in subjects with PCOS.