In women with PCOS, the impact of metformin on testosterone and FAI positively correlated with the changes in LH (testosterone: r = 0.40 (p = 0.0004); FAI: r = 0.46 (p = 0.0002)) and with the changes in the LH/FSH ratio (testosterone: r = 0.38 (p = 0.0015); FAI: r = 0.41 (p = 0.0006)). This evidence concerns the gene PLOD1 and polycystic ovary syndrome.