Abstract
Background: Hyperthyroidism is one of the important causes of high-output failure and reversible pulmonary artery hypertension. Severe pulmonary artery hypertension is rarely found in associated with hyperthyroidism due to the small number of cases reported. We present an interesting case with multiple unexpected findings of the possible causes of severe pulmonary artery hypertension: hyperthyroidism, pulmonary embolism, and ostium secundum atrial septal defect.
Case Report: We present the case of a previously healthy rural Thai man who progressively developed dyspnea on exertion, chronic diarrhea, and jaundice for the previous 3 months. Physical examination revealed right-sided predominate chronic heart failure with signs of pulmonary hypertension. The investigation demonstrated autoimmune hyperthyroidism, cholestatic jaundice, moderate tricuspid regurgitation, ostium secundum atrial septal defect, and severe pulmonary artery hypertension. After treatment with an anti-thyroid drug and closure of the ostium secundum atrial septal defect, his symptoms of jaundice and pulmonary artery pressure were completely resolved.
Conclusions: Severe pulmonary artery hypertension may not solely be a result of hyperthyroidism. Further investigation for other causes is recommended.

Keywords: Hypertension, Pulmonary, Ostium Secundum Atrial Septal Defect, hyperthyroidism, Pulmonary Embolism