After confirming that the haptoglobin genotype was distributed according to Hardy-Weinberg equilibrium in both PCOS patients and controls (data not shown), we found that the Hp2 allele was more frequent in the former (62% vs 52%, χ2 = 5.191, P = 0.023), explaining a borderline significant tendency towards a higher frequency of Hp2/Hp2 genotype, and to a reduced frequency of the Hp1/Hp1 genotype, in PCOS patients compared with the controls (Table 3). This evidence concerns the gene HP and polycystic ovary syndrome.