In rodent models of PAH secondary to serotonergicexcess—including after administration of the anorexigen dexfenfluramineimplicated in drug-induced PAH—CYP1B1 and 16-estrogen levels are increased,while genetic knockout or pharmacologic inhibition of CYP1B1 prevents disease[82, 83]. This evidence concerns the gene CYP1B1 and pulmonary arterial hypertension.