SERPINE1 and polycystic ovary syndrome: When we analysed individual sized follicles for PAI-1 expression in PCOS and control ovaries, there was a statistically significant increase in this marker as the follicles developed from small (primordial and primary) through to preantral (medium) follicles in both the control (p = 0.03 for % of follicular staining/Area Fraction ROI; p = 0.02 for Mean Colour Intensity of follicles) and in PCOS ovaries (p = 0.01 for % of follicular staining; p = 0.009 for Mean Colour Intensity of follicles) (Table 3 and Fig. 5 a).