The level of endothelin-1 constantly rose from subjects with mild PAH, moderate PAH, to severe PAH (mean ± SD: 587.52 ± 388.93 pg/dL, 613.57 ± 297.38 pg/dL to 948.09 ± 563.13 pg/dL, consecutively, p value = 0.071). This evidence concerns the gene EDN1 and pulmonary arterial hypertension.