Prospective echocardiographic evaluation of patients with endogenous subclinical hyperthyroidism and after restoring euthyroidism.

OBJECTIVES: Clinical significance of, and the need for, treatment in subclinical hyperthyroidism (sHT) is still a matter of debate. The aim of the study was to assess the impact of sHT on echocardiographic parameters.
DESIGN: Patients with endogenous sHT of nonautoimmune origin underwent full echocardiographic assessment at diagnosis and after restoring euthyroidism with radioiodine treatment. PATIENTS: Studied group consisted of 44 patients (37 women, 7 men), aged 22-65 years (mean 45·9±11·0). MEASUREMENTS: Full echocardiographic assessment included estimation of cardiac chamber diameters and volume as well as cardiac contractility, according to the guidelines of the American Society of Echocardiography. Left ventricular mass was calculated according to Penn's convention. For estimation of left ventricle diastolic function, the following echocardiographic parameters were obtained: maximal early filling wave velocity (E), maximal late filling wave velocity (A), E/A ratio, isovolumetric relaxation time and early filling wave deceleration time.
RESULTS: In the studied group, phase of sHT was associated with increased volume of heart chambers, increased diameter of ascending aorta, increased left ventricle mass and disturbed left ventricle relaxation (P<0·05). The systolic function of the left ventricle was unaffected; however, the ejection time was shortened. The changes were reversible with restoring biochemical euthyroidism (P<0·05). Moreover, a significant correlation between some of the parameters and thyroid hormones concentration was demonstrated.
CONCLUSIONS: sHT was associated with significant changes in echocardiographic parameters, which may contribute to increased cardiovascular risk in these patients. The alterations were reversible with restoring biochemical euthyroidism, what supports the necessity of treatment introduction in sHT.