C3 and Insulin resistance: In conclusion, in a non-obese PCOS population matched for age, insulin resistance, and inflammation, initiating proteins of the classical and alternate complement cascades were increased in women with PCOS, but their positive correlation with 25(OH)D3 was only seen for C3b in control women, with no correlation to 1,25(OH)2D3, suggesting that the increase in complement proteins in women with PCOS is independent of vitamin D.