Prevalence and Features of the Polycystic Ovary Syndrome
This article suggests a prevalence as high as 8% of PCOS which puts it as the most common endocrine abnormality of reproductive aged women in the US. PCOS has been linked very strongly to insulin resistance.
This link seems to come from elevated insulin affecting 15,20 lyase, the enzyme that converts testosterone to estrogen. So, elevated insulin slows conversion to estrogen, essentially rising levels of testosterone which messes up the ovulation process. The problem is that PCOS has traditionally been treated with oral contraception, which is know to worsen insulin resistance. Another perfect example of how we can actually screw the body up worse if we try to override human physiology instead of balance it.
JCEM — Abstracts: Azziz et al. 89 (6): 2745 –