yperthyroidism has been associated with cardiomyopathy and heart failure (HF). This study aims to evaluate clinical, laboratory and echocardiographic parameters, at admission and 12 months following euthyroidism restoration, in patients with hyperthyroidism-associated HF. Mechanisms underlying hyperthyroidism-associated HF and the outcomes of echocardiographic parameters along the study period are both discussed. Materials & Methods: Patients with newly diagnosed overt hyperthyroidism and HF (Group 1), age and sex-matched euthyroid HF subjects (Group 2), and a control group were enrolled. Results: In the 38-month study period, 56 patients were admitted for hyperthyroidismassociated HF, of whom 71% had a pre-existing, mainly hypertensive, cardiomyopathy vs 68% of Group 2 subjects. Mean heart rate was significantly higher in Group 1 than Group 2 (127±38 vs 110±17bpm; P <0.02); 30 Group 1 (54%) and 16 (29%) Group 2 patients presented with atrial fibrillation. At admission, left ventricular ejection fraction (LVEF), end diastolic (LVEDD) and end systolic (LVESD) diameters were lower, whilst LV mass (LVM), interventricular septum thickness (IVST) and LV posterior wall thickness (LVPWT) were increased in both Groups compared to controls. At the end of the study, despite achievement of euthyroidism in all hyperthyroid patients, mean LVEF was not significantly different in Group 2 but was significantly lower in Group 1 patients compared to controls; LVM, IVST and LVPWT did not change in both study groups. Conclusion: In our series, newly diagnosed hyperthyroidism-associated HF had 2.4% prevalence. At the end of the study, LVEF significantly improved in euthyroid, but not in hyperthyroidism-associated HF patients compared to controls.