The main purpose of this clinical trial is to examine the feasibility and effects of
fulvestrant in post-menopausal women with pulmonary arterial hypertension (PAH). The study
will evaluate how well the drug is tolerated. The study will evaluate changes in circulating
hematopoietic progenitor cells, plasma hormone levels, NT-proBNP, and other plasma biomarkers
after the administration of fulvestrant. Changes in tricuspid annular plane systolic
excursion, stroke volume index, right ventricular fractional area change, and other echo
parameters after fulvestrant administration will be evaluated as well as changes in distance
walked in six minutes.