TGF-β1 promoter hypomethylation at CpG4 and CpG7 was associated with IR in PCOS patients. Lower methylation levels correlated with higher HOMA-IR and FINS. No significant correlation between TGF-β1 methylation and mRNA/protein expression. Higher testosterone levels were observed in the high-methylation PCOS group. The gene discussed is TGFB1; the disease is polycystic ovary syndrome.