ESPE Abstracts

Background: Subclinical hypothyroidism (SH) is defined as an elevated serum concentration of TSH when serum free thyroxine (fT₄) concentration is within its reference range. Impaired myocardial contractility in overt hypothyroidism and left ventricular (LV) diastolic dysfunction in adults with SH as well as beneficial effects of thyroid hormone replacement on systolic and diastolic functions in adults with SH has been documented, however the presence of similar alterations in children with SH is still under debate.

Objective and hypotheses: To evaluate cardiac functions of children with subclinical hypothyroidism (SH) before and after L-thyroxine (LT₄) replacement using M-mode and tissue Doppler echocardiography (TDE).

Method: Children with SH together with age- and sex-matched healthy children were enrolled in the study. At baseline and 6 months after euthyroidism was achieved M-mode and TDE were performed and left ventricular functions were evaluated. Pre-treatment data of the SH group was compared with those of controls and post-treatment parameters.

Results: Thirty-one children with SH and 32 healthy children were enrolled in the study. In M-mode echocardiography interventricular septum thickness and left ventricle mass index were slightly increased in SH group than controls (P<0.05). In the SH group none of the M-mode echocardiography-derived parameters have changed after LT₄ treatment (P>0.05). In TDE, patients with SH had a significantly lower E_m’ and a higher E/E_m’, isovolumic relaxation time (IVRT), isovolumic contraction time (IVCT) and myocardial performance index (MPI) than the control group (P<0.05). Six months after euthyroidism was achieved TDE showed a significant increase in E_m’ and a significant decrease in IVRT, IVCT and MPI.

Conclusion: The result of this study showed that SH was associated with pre-clinical alterations in left ventricular function as compared to healthy individuals and LT₄ treatment improved left ventricular TDI functional parameters.