C3 and polycystic ovary syndrome: C3a acts as an inflammatory mediator and was elevated in both obese and nonobese PCOS, whilst C3b did not differ in either obese or nonobese PCOS; however, its cleavage product iC3b, which prevents amplification of the alternative pathway [22], was increased in both obese and nonobese PCOS, thereby inhibiting the alternative pathway.