Effects of TSH-suppressive therapy on cardiac morphology and function: beneficial effects of the addition of beta-blockade on diastolic dysfunction

OBJECTIVE: To investigate the effects of long-term levothyroxine (LT4) suppressive therapy on the heart and the effects of beta-blockade on cardiac functions. DESIGN: Twelve female patients receiving LT4, selected from a group of patients with TSH levels of 0.1-0.4 microU/ml, were evaluated. The control group consisted of 11 healthy subjects and 12 patients with TSH levels <0.05 microU/ml. METHODS: Cardiac evaluation consisted of a 12-lead electrocardiogram and an echocardiographic study. Left ventricular mass index (LVMI), isovolumetric relaxation time (IVR), left ventricular end systolic (LVESD) and diastolic diameters, early (VE) and late (VA) diastolic flow velocities and fractional shortening were evaluated. Exercise capacity was assessed with a bicycle ergometer. Both work load and maximal exercise time were measured. Atenolol was given to the patient group at a dosage of 50 mg/day for 3 months and evaluations were repeated. RESULTS: On basal evaluations, LVMI (96+/-17 vs 78+/-21 g/m(2)) and IVR (101+/-9 vs 91+/-4 ms) were found to be increased in the patients taking LT4 (P<0.01). LVESD was also lower than controls (P<0.05). A decrease in VE and an increase in VA were also observed in the patients (P<0.01). IVR decreased after atenolol (92+/-10 vs 101+/-9 ms, P<0.05). LVMI decreased and VE and VA improved but did not reach statistical significance after beta-blockade. Baseline work load and maximal exercise duration were significantly lower in the patients and improvements were observed after atenolol treatment. CONCLUSIONS: These results indicated that cardiac dysfunction may occur even when TSH is suppressed to 0.1-0.4 microU/ml with LT4. beta-blockade improved the cardiac functions.