The definition of polycystic ovary syndrome (PCOS) has been based on a combination of three characteristics ever since Stein and Leventhal described the first cases in 1935. At that time, no methods for serum androgen measurement were available and the disorder was based on enlarged polycystic ovaries, acne, hirsutism and amenorrhoea. Since then, there have been numerous attempts at defining the syndrome, all of which have attempted to be as inclusive as possible of the myriad of phenotypes that comprise PCOS. There have been three formal definitions over the past two decades that have proposed a combination of clinical, biochemical and imaging criteria (see Table 10.1) but these, as we have argued in the past, are still too vague to pin down the syndrome.

Hyperandrogenism in the context of PCOS is a term used loosely to encompass both the clinical features of acne, hirsuties and androgenic alopecia and the laboratory evidence of hyperandrogenaemia. The clinical features are due to androgenic stimulation of the cutaneous pilosebaceous unit but the nature of acne, hirsuties and balding demonstrates that, even within an individual, the response is heterogeneous, so wide variations between women can only be expected and this defies an easy definition. The problem with hyperandrogenaemia is no easier: which androgen(s) should be measured, how often should it/they be measured and when in the menstrual cycle. There also remains the confusion created by the imprecise use of the terms hyperandrogenism and hyperandrogenaemia.