Objectives To evaluate the effect of thyroid hormone therapy with low dose of thyroxin on cardiac function in elderly patients with heart failure and sick euthyroid syndrome.Methods Forty-seven patients(33 males and 14 females,mean age 85.9±4.6 years, ranging from 80 to 99 years)with chronic heart failure(NYHAⅡ-Ⅳ)and low triiodothyronine(T_3)state were randomly allocated to the treatment group or control group.The treatment group patients received oral administration of levothyroxine sodium(Euthyrox)25-50 mg/d in addition to conventional therapy of heart failure,whereas patients in control group were given conventional therapy only.Serum level of total T_3(TT_3),free T_3(FT_3),total thyroxine(TT_4),free thyroxine(FT_4),and thyroid-stimulating hormone(TSH)were determined.For both groups,left ventricular ejection fraction(LVEF)and stroke volume(SV)were assessed by two-dimensional echocardiography before and at 8 weeks after treatment.The changes of these parameters after the treatment were evaluated by adjusting heart rate in the two groups.Results The reduced serum T_3 level in the treatment group was corrected after thyroid hormone therapy, and these patients had a significant improvement in cardiac function after treatment.By contrast,in the control group only changes of serum TT_3 and TT_4 levels and SV and LVEF after treatment were statistically significant.The heart rate-adjusted mean SV and LVEF in both groups were also increased,which was significantly greater in the treatment group than in the control group.Conclusion In the elderly patients with heart failure and sick euthyroid syndrome,addition of thyroxine at a low dosage to the conventional treatment could effectively improve the low T_3 state and cardiac function independent of changes of heart rate. Objectives To evaluate the effect of thyroid hormone therapy with low dose of thyroxin on cardiac function in elderly patients with heart failure and sick euthyroid syndrome. Methods Forty-seven patients (33 males and 14 females, mean age 85.9 ± 4.6 years, ranging from 80 to 99 years) with chronic heart failure (NYHA II-IV) and low triiodothyronine (T_3) state were randomly allocated to the treatment group or control group. The treatment group patients received oral administration of levothyroxine sodium (Euthyrox) 25-50 mg / d in addition to conventional therapy of heart failure, in patients in control group were given conventional therapy only. Serum level of total T_3 (TT_3), free T_3 (FT_3), total thyroxine (TT_4), free thyroxine (FT_4), and thyroid- stimulating hormone (TSH) were determined. For both groups, left ventricular ejection fraction (LVEF) and stroke volume (SV) were assessed by two-dimensional echocardiography before and at 8 weeks after treatment. These changes of these parameters after the treatme nt were evaluated as adjusting heart rate in the two groups. Results The reduced serum T_3 level in the treatment group was corrected after thyroid hormone therapy, and these patients had a significant improvement in cardiac function after treatment. By contrast, in the control group only changes of serum TT_3 and TT_4 levels and SV and LVEF after treatment were significant significant. The heart rate-adjusted mean SV and LVEF in both groups were also increased, which was significantly greater in the treatment group than in the control group. Confluence In the elderly patients with heart failure and sick euthyroid syndrome, addition of thyroxine at a low dosage to the conventional treatments could effectively improve the low T_3 state and cardiac function independent of changes of heart rate.