ALOX5 and pulmonary arterial hypertension: The increased level of 13(S)-hydroperoxy-9Z,11E-octadecadienoic acid (E,E-13-HpODE) in the group of men with PAH compared to healthy men may suggest increased oxidation of linoleic acid (LA) by enzymes such as 5-lipoxygenase (5-LOX) and 15-lipoxygenase (15-LOX) to compounds such as 9-hydroxyoctadecadienoic acid (9-HODE) and 13-hydroxyoctadecadienoic acid (13-HODE).