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Departments of Endocrinology (J.A.S., H.E.V.) and Internal Medicine (F.G.V., B.G.), Marilia Medical School and Department of Endocrinology, Faculdade Ciências Médicas Pontifícia Universidade Católica de Campinas (J.H.R.), São Paulo, Brazil 04029-000
Address all correspondence and requests for reprints to: Prof. João Hamilton Romaldini, Avenida Indianopólis, 530. CEP 04062-000, São Paulo, Brazil. E-mail: jhroma{at}netpoint.com.br.
Subclinical hyperthyroidism has been associated with harmful cardiac effects, but its treatment remains controversial. This study was designed to assess the cardiac effects of the normalization of serum TSH concentration in patients with endogenous subclinical hyperthyroidism. Ten patients (median age, 59 yr; range, 16–72 yr) with normal serum free T4 and free T3 concentration and a stable suppression of serum TSH levels were evaluated by Doppler-echocardiography, by standard and 24-h electrocardiography monitoring (Holter), and by the clinical Wayne index. Ten subjects, matched for age and sex, were used as controls. Patients were reevaluated 6 months after achieving stabilized euthyroidism by using methimazole with a median initial dose of 20 mg daily (10–30 mg daily). After reaching euthyroidism, we found a significant decrease in the heart rate (P = 0.008), the total number of beats during 24 h (P = 0.004), and the number of atrial (P = 0.002) and ventricular (P = 0.003) premature beats. Echocardiographical data resulted in a reduction of the left ventricular mass index (P = 0.009), interventricular septum thickness (P = 0.008), and left ventricular posterior wall thickness (P = 0.004) at diastole. Furthermore, the early diastolic peak flow velocity deceleration rate was significantly higher (P = 0.02) in the untreated patients compared with controls. The Wayne clinical index was higher in patients than in controls (P = 0.001) and decreased after treatment (P = 0.004). Serum TSH concentration returned to normal values after 2.5 months (range, 1.0–7.0 months) on methimazole therapy (0.05 vs. 1.42 mU/liter; P = 0.002). Serum free T4 values were normal in patients before treatment but significantly decreased after reaching the euthyroidism (16.9 vs. 11.5 pmol/liter; P = 0.002). In contrast, serum free T3 concentration did not differ among the groups. In conclusion, our findings support that early antithyroid therapy should be considered in patients with endogenous subclinical hyperthyroidism, where it is needed to prevent potential progression to a more advanced heart disease.
This work was presented in part at the 12th International Thyroid Congress, Kyoto, Japan, 2000.
Abbreviations: 2D, Two-dimensional; E/A, early to late diastolic peak flow velocity ratio; FT3, free T3; FT4, free T4; MMI, methimazole; peak A, late diastolic peak flow velocity; peak E, early diastolic peak flow velocity; TPOAb, antithyroidperoxidase antibodies; TRAb, TSH-receptor antibodies.
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