| Maciel et al., Sao Paulo, Brazil, measured systolic and diastolic function, using Doppler echocardiography in 11 patients with subclinical hypothyroidism (mean TSH 10.9 mU/ml) before and 3 and 6 months following restoration of the euthyroid state. The following parameters were measured: heart rate, systolic fractional shortening, ejection fraction, pre-ejection period, and different diastolic parameters as well. They could not find any abnormality at baseline, neither any change or abnormality after restoration of the euthyroid state. (Comment: Concerning possible abnormalities of left ventricular function in subclinical hypothyroidism controversy exists in the literature. Maybe that more sensitive methods are necessary to solve the controversy.) The reverse situation was evaluated by Sherman et al., Houston, TX, USA, who investigated cardiac effects of suppressive doses of T4 in 17 asymptomatic patients treated for thyroid carcinoma and compared results to 17 euthyroid matched controls, using resting M-mode, 2-dimensional and Doppler cardiography. No differences were found in resting heart rate, left ventricular mass, fractional shortening, stroke volume, or ejection fraction. Also diastolic function according to isovolumic relaxation time, E/A ratio, and atrial fractional filling were not different between the groups. There was only a minimal effect of T4 suppressive therapy on systolic time intervals. (Comment: The controversy with regard to present or absent effects on left ventricular function in patients on T4 suppressive therapy is moving towards negative findings. Since the original report of Biondi et al. several years ago, about 4 other reports show now absent or only minimal effects, and this is on of them.) |
