We found that vitamin D supplementation at a dosage of 4000 IU/day for 12 weeks to insulin-resistant women with PCOS had beneficial effects on total testosterone, SHBG, FAI, hs-CRP and TAC levels compared with 1000 IU/day of vitamin D and placebo groups, but did not affect DHEAS, NO, GSH and MDA levels. This evidence concerns the gene SULT2A1 and polycystic ovary syndrome.