C3 and obesity due to melanocortin 4 receptor deficiency: In the obese control women, BMI correlated with C3, C3desArg, C3a, C3d, C4, factor I, factor B, C5a and C5 whilst, in the nonobese control women, BMI only correlated negatively with C1q, again suggesting that the complement protein changes are due to a combination of those inherent in the pathophysiology of PCOS as well as due to additional physiological factors such as obesity.