The Effect of Bosentan and Pioglitazone on Insulin Resistance in Pulmonary Arterial Hypertension ,is a study evaluating the incidence of insulin resistance in patients with pulmonary hypertension and testing the utility of a validated PH therapy(Tracleer) versus Pioglitazone in the treatment of those patients found to have insulin resistance.Patients with PAH must be stable on therapy for at least 3 months are considered for enrollment in this study.With the exception of PAH, subjects must be free of major medical illnesses, including diabetes mellitus ,malignancy or significant hepatic or renal disease.