How much insulin resistance in polycystic ovary syndrome? Comparison of HOMA-IR and insulin resistance (Belfiore) index models

INTRODUCTION: Polycystic ovary syndrome (PCOS), the commonest endocrinopathy of women in reproductive age, is often accompanied by insulin resistance (IR), hirsutism and/or fertility problems. The aim of the study was to assess the prevalence of IR in women diagnosed with PCOS. MATERIAL AND METHODS: The study involved 137 women diagnosed with PCOS, according to the Rotterdam consensus criteria (2003). Insulin resistance was assessed according to the HOMA-IR method and insulin resistance (Belfiore) index (IRI) derived from glucose and insulin during the oral glucose tolerance test. RESULTS: There was a significant (p < 0.0001) but relatively moderate correlation between IRI and HOMA-IR (r = 0.5 and r = 0.57 for a linear and non-linear model, respectively). Insulin resistance was more prevalent according to IRI (49.6%) than according to HOMA-IR (22.6% and 15.8% for 3.46 and 3.8 cut-off points, respectively, p < 0.01). The majority of patients with high HOMA-IR also had high IRI (e.g. 86%, for HOMA > 3.8), but the majority of patients with raised IRI would not be diagnosed as insulin resistant according to HOMA (61.7% and 73.5%, for HOMA-IR(3.46) and HOMA-IR(3.80), respectively). CONCLUSIONS: The insulin resistance (Belfiore) index indicates more cases of insulin resistance than HOMA-IR in women with PCOS. Therefore, detection of insulin resistance among women with PCOS is highly method-dependent with more severe cases being detected with HOMA-IR than with IRI.