RBP4 and polycystic ovary syndrome: The heterogeneity of results obtained in studies of RBP4 in women with PCOS may be attributed to factors including different cohorts studied (obese vs non-obese; normoandrogenic vs hyperandrogenic; normal vs IGT; population-based vs hospital-based study population), differences in criteria in selection of women with PCOS (either Rotterdam or NIH criteria), methodological differences in measurements of RBP4 levels (Western blot vs ELISA) and differences in the methodologies used for assessing insulin resistance (OGTTs vs clamp studies) (15).