OBJECTIVE: Previous experimental studies have provided evidence showing that 
changes in thyroid hormone signaling correspond to alterations in myocardial 
function in animal models of heart failure. The present study further explores 
whether thyroid hormone alterations are correlated with the functional status of 
the myocardium in patients with heart failure.
METHODS: In this study, 37 patients with mean ejection fraction (EF%) of 26.2 
(8.2) were included. Myocardial performance was assessed by echocardiography and 
cardiopulmonary exercise testing. Total tri-iodothyronine (T3), thyroxine, and 
TSH levels were measured in plasma.
RESULTS: Total T3 was strongly correlated with VO2max (r = 0.78, P = 2 x 
10(-8)). Furthermore, multivariate analysis revealed that total T3 was an 
independent predictor of VO2max (P = 0.000 005). A weaker but significant 
correlation was also found between total T3 and EF% (r = 0.56, P = 0.0004), 
systolic (r = 0.43, P = 0.009) and diastolic (r = 0.46, P = 0.004) blood 
pressure.
CONCLUSIONS: changes in thyroid hormone were closely correlated to myocardial 
functional status in patients with heart failure. These data probably indicate a 
possible role of thyroid hormone in the pathophysiology of heart failure and 
confirm previous experimental reports.