GSTM1 and essential hypertension: Some studies have shown that GSTM1 [25, 26, 47, 48] and/or GSTT1 [26, 27, 48–51] were associated with essential hypertension risk, other authors have shown that only the double deletion GSTM1/GSTT1 was associated with essential hypertension risk, and other failed to confirm any association [29].