C3 and diabetes mellitus: Increased levels of complement C3 have a greater association with insulin resistance than markers of inflammation such as C-reactive protein [55], and a recent study has shown a strong association of serum complement C3 with serum insulin and insulin resistance in subjects with PCOS, suggesting that this inflammatory marker might predict future diabetes and CVD complication risk in subjects with PCOS [56]; therefore, it is not surprising that, in this study, complement C3 was also elevated in PCOS versus controls.