ESR1 and pulmonary arterial hypertension: For instance, gene expression data from one patient cohort demonstrated an up-regulation of ESR1 in human PAH subjects relative to controls.21 Polymorphisms in ESR1 have also been associated with an increased risk of developing portopulmonary hypertension independent of gender.4 Uniquely, we report here that ERα expression is markedly increased in human PASMCs from female PAH patients compared with male, while ERβ expression is greatest in PASMCs from male PAH patients.