Cardiovascular effects of long-term L-thyroxine therapy for Hashimoto's thyroiditis in children and adolescents

Morphology and function of the left ventricle were evaluated by echo and Doppler examination in 16 females affected by Hashimoto's thyroiditis, aged 13.3 (4.5) years (range 7.9-24.6). They were on L-thyroxine (L-T4) treatment for a period of 2.8 (2.8) years (range 0.8-7.6) with a mean daily dose of 77 (18) micrograms/m2. Left ventricular mass, systolic and diastolic function, cardiac output and systemic vascular resistance did not differ from a control group matched for age, sex and body size. A further analysis of the patients according to thyrotrophin serum levels (less or more than 0.1 mU/l) gave similar results. Moreover, no relationship was found between echocardiographic findings and age, L-T4 daily doses, duration of treatment and serum level of thyroid hormones. We can therefore conclude that chronic L-T4 treatment for Hashimoto's thyroiditis at the given doses did not affect cardiac function and morphology in children and adolescents; however, a longer follow-up is needed before confirming the safety of this therapy in the long term.