Commonalities in fluctuations in signal transduction pathways in human IPAH and the mouse PAH model were confirmed in the following pathways: upregulation of Janus kinase/signal transducers and activators of the transcription (JAK/STAT) pathway, the hemostasis pathway, the estrogen receptor pathway, and the serotonin receptor pathway, and down-regulation of the vascular endothelial growth factor (VEGF) pathway, the platelet-derived growth factor (PDGF) pathway, apoptosis, and the BMP signaling pathway. This evidence concerns the gene ESR1 and idiopathic pulmonary arterial hypertension.