MTHFR and hypertensive disorder: After stratification by rs1801133 genotypes, lower MTHFR promoter methylation quartiles (<Q1, Q1–Q2, Q2–Q3) compared to ≥Q3 were significantly associated with a higher risk of hypertension among individuals carrying the CC genotype: ORs (95% CIs) = 3.225 (1.140–9.124), 4.177 (1.424–12.247), and 8.645 (2.513–29.739) for Q2–Q3, Q1–Q2, and <Q1, respectively.