BACKGROUND: Although an altered thyroid metabolism has been documented in 
patients with overt heart failure, no evaluation has been made of a 
heart-thyroid interaction in mildly symptomatic patients with idiopathic left 
ventricular dysfunction (ILVD). We wanted to assess the thyroid state in 
patients with ILVD.
METHODS AND RESULTS: Eighty-six patients (age 60 +/- 10 years) were enrolled 
into the study. Thyroxine (T4), triiodothyronine (T3), thyrotropin, brain and 
atrial natriuretic peptides (BNP, ANP), noradrenaline, aldosterone, renin 
activity, and interleukin-6 were measured. Patients were divided into three 
groups: Group N with LV ejection fraction (EF) > or = 50% (n = 28), Group I with 
LVEF > 35%-< 50% (n = 34), Group II with LVEF < or = 35% (n = 24). There was a 
significant correlation between T3 and LVEF (r = 0.25, P = .02) and a negative 
correlation between T3 and BNP (r = -0.37, P < .0001). At univariate analysis T3 
was a predictor of LV dysfunction, whereas BNP was the most important predictor 
at multivariate analysis (P = .002). T3 was the only predictor of New York Heart 
Association class at multivariate analysis.
CONCLUSION: An altered thyroid profile characterized by a reduction in 
peripheral production of biologically active T3 is related to LV dysfunction and 
early symptoms of heart failure in patients with ILVD.