MTHFR and essential hypertension: The results of genetic balance test showed that the distribution of MTHFR C677T genotype in the four groups was in genetic balance (H-type hypertension group, χ2 = 2.089, p = 0.352; essential hypertension group, χ2 = 0.288, p = 0.866; isolated Hyperhomocysteinemia group, χ2 = 0.380, p = 0.827; control group, χ2 = 1.612, p = 0.447), indicating that the enrolled subjects were genetically, representative of the Tibetan population in Tibet.