Hyperthyroidism: a rare cause of reversible pulmonary hypertension.

We describe a case of pulmonary hypertension and high-output heart failure in a 61-year-old woman suffering from relapsing Graves disease. The patient experienced prompt hemodynamic and symptomatic recovery after normal thyroid function was restored. Possible mechanisms for the development of pulmonary arterial hypertension due to hyperthyroidism include damage to pulmonary vascular endothelium due to high cardiac output or an autoimmune process or increased metabolism of intrinsic pulmonary vasodilators. Another possible mechanism is vascular vasoconstriction due to decreased cholinergic output.