Subtle diastolic dysfunction in children with idiopathic subclinical hypothyroidism: effect of two years of l-thyroxine treatment.

PURPOSE: Data about clinical implications of subclinical hypothyroidism (SH) in children are scanty, and the management of this condition is still challenging particularly for mild forms (TSH levels ranging between 4.5 and 10 mU/L). Aim of this study is to compare left ventricular (LV) geometry and function in SH children and matched euthyroid controls, and to evaluate the cardiac effects of L-thyroxine (L-T4) therapy.

METHODS

Thirty-six children (19 females), aged 8.3 ± 0.7 years, with persistent and idiopathic SH were enrolled in the study. Thirty-six euthyroid children comparable for sex, age and body mass index were enrolled as controls. Baseline echocardiography and biochemical assessment was performed in all subjects. Thereafter, SH children started L-T4 therapy. Both assessments were repeated after 2 years of therapy in patients and 2 year -follow-up in controls.

RESULTS

The LV cavity size was comparable between SH and controls, at baseline, and increased similarly over time. LV systolic function was normal at baseline in both groups and remained comparable at end-study. With regard to diastolic function, SH children showed a significant prolongation of isovolumic relaxation time (IVRT) compared with controls (92.95 ± 3.74 vs 76.13 ± 2.75 msec, p = 0.0006), with normal E/A and E/E' ratios in both populations, consistent with subclinical, mild diastolic dysfunction. After L-T4 therapy, IVRT significantly decreased (81.43 ± 4.28 msec p < 0.05) becoming similar to controls (82.20 ± 2.14 msec).

CONCLUSION

Long-lasting mild SH in children is associated with subtle abnormality of LV relaxation which improves with L-T4 therapy. Whether these subtle alterations may lead to significant clinical consequences require further investigation.