SERPINE1 and idiopathic pulmonary arterial hypertension: Our hypothesis is supported by a previous study where significantly increased t-PA antigen and t-PA activity in correlation with mPAP, as well as increased PAI-1 activity, was reported in women with IPAH, and this presence of gender differences in the plasmin- and thrombin-activation system in IPAH leading to an antifibrinolytic/prothrombotic state was suggested as a possible explanation for the female predominance in the disease.[15]