Even mild changes in free thyroxine could influence the degree of heart failure measured by its biological surrogates

Both, severe hypo- or hyperthyroidism may alter hemodynamic parameters. The aim of our study was to ascertain, whether also distinct changes within normal range of free thyroxine (fT4) would be associated with an impairment of left ventricle function in patients with chronic heart failure. Hundred-forty-eight patients (m121, f27, mean age 63.8 +/- 1.14 years) with chronic heart failure, fT4 levels within the normal range (9-22 pmol/l) and without thyrostatics or substitution treatment. Degree of heart failure was quantified by plasma B-type natriuretic peptide (BNP) and N-terminal pro-BNP (NT-proBNP). Patients with fT4 in the range 11.9-14.6 pmol/l [optimal, second-third quintile] had significantly lower NT-proBNP (718 +/- 70.4 pg/ml), than those with fT4 < or = 11.8 [low-normal, bottom quintile](1236 +/- 223.6 pg/ml; p<0.03) and those with fT4 over 14.6 pmol/l [high-normal, top two quintiles] (1192 +/- 114.9 pg/ml; p<0.0002). These differences remain significant, also if adjusted for age, gender and other confounders; adjusted odds ratio was 1.30 (1.05-1.59) for optimal vs. low-normal and 1.27 (1.04-1.55) for optimal vs. high-normal. Similar statistical differences were also found in BNP, but only when optimal and high-normal fT4 ranges were compared. In conclusion, the severity of heart failure seems to be also influenced by only mild deviations of fT4 concentrations from optimal levels.

[Epidemiological study of hypothyroidism as cardiovascular risk in population]

BACKGROUND

Prevalence of hypothyroidism (HT) markedly differs among various populations. We aimed to establish the prevalence of HT in the Czech population and to assess its association with conventional cardiovascular risk factors.

METHODS AND RESULTS

1240 subjects (629 m, 611 f; mean age 52.3); a random, population-based sample were evaluated. Cut-off points for thyroid parameters were defined as follows: thyreostimulating hormone (TSH) 0.58-3.65 mU/I, free thyroxine (fT4) 9-22 pmol/l and thyroid peroxidase antibodies (TPOAb) < or = 14 IU/A. The overall prevalence of HT was 6.8% in males and 13.8% in females (p < 0.0001); subclinical HT (high TSH, normal fT4) was found in 3.0% and 8.0%, overt-untreated (high TSH, low fT4) in 3.2% and 3.0% and overt-treated HT in 0.6% and 2.8% of males and females, respectively. Moreover, in euthyroid subjects, 4.6% of males and 9.3% of females showed positive TPO-Ab (p < 0.0001). The adjusted relative risk of hypothyroidism was significantly increased in males with manifest vascular disease (odds ratio 3.48 (1.56-7.74)]), in females aged > or = 55 years (2.08 (1.29-3.36)) or hypertension (1.80 (1.03-3.13)), and moreover, in males and females with positive TPOAb (5.81 (2.57-13.13) and 5.92 (3.38-10.36), resp.)

CONCLUSIONS

Hypothyroidism was found in Czech population highly prevalent and it can contribute to the coronary risk, produced by conventional factors.