NRG4 and polycystic ovary syndrome: Moreover, Chi3l1 plays an important role in insulin resistance and diabetes, which closely correlates with glypican-4 (GPC-4), neuregulin-4 (NRG4), body mass index (BMI), the waist-to-hip ratio (WHR), and homeostasis model assessment of insulin resistance (HOMA-IR) in women with PCOS [282].