Abstract： Objective To analyze changes of cardiac enzyme and euthyoid function variation in hypertension patients treated with oral pioglitazone.Methods Indications of pioglitazone,characteristics of cardiac injury and prognosis of patients were reviewed in 5 CaSeS between 2002 March and 2006 May.Free tfiiodothyronine (FT3),Free thyroxine(FT4),cardiac enzyme and were determined in patients.Results Five patients had an chronic increase in cardiac enzyme within(90-120)days of starting oral pioglitazone.The peak of GOT was(180±45)U/L and CPK was(540±60)U/L.Discontinuation of pioglitazone resulted in decrease in cardiac enzyme levels to baseline values within(24±7)days.Drugs cardiotoxicity showed decrease of Free triiodothyronine and Free thyroxine.Conclusion It is important to identify pioglitazone as a potential cause of euthyoid function variation and cardiace enzyme.Accordingly,it is necessary to monitor cardiac function and the change of myocardium enzyme after longterm oral pioglitazone.