MTHFR and hyperhomocysteinemia: It turned out that individuals with either heterozygous “CT” or homozygous “TT” variant genotype of MTHFR 677 who also had blood Pb levels greater than 10 μg/dL, had significantly increased risk for hyperhomocysteinemia [OR (95% CI) 2.36 (1.42–3.9); p value = 0.001] compared with those having “CC” genotype of MTHFR 677 with blood Pb levels less than or equal to 10 μg/dL, even when the model was adjusted for age, gender, folate and vitamin B12 (Table 7).