Endocrine Abstracts

Background: The management of subclinical hypothyroidism (SH) is still challenging in particular for mild forms with TSH levels ranging between 4.5 and 10 mU/L. Although SH in children seems to be a bening condition, ongoing scientific investigations have highlighted the presence of subtle proatherogenic abnormalities among children with modest elevations in their TSH levels. Data on cardiac performance in children with SH are still scanty.

Aim: To compare left ventricular (LV) geometry and function of SH subjects in comparison to healthy comparable controls before and after a trial with levo-thyroxine (L-T₄) therapy.

Methods: Thirty-six (36) children (19 females and 17 males), aged 8.5±0.6 years, with persistent SH (at least 2 years) and 36 euthyroid matched controls were enrolled in the study. At study entry height, BMI, heart rate (HR), systolic (SBP) and diastolic bloody pressure (DBP) were assessed and Doppler echocardiography was performed in all subjects. Twenty-two SH children, who accepted to start L-T₄ therapy, were reevaluated after 2 years of treatment and 22 matched controls were observed throughout the same period.

Results: LV size and systolic function were comparable between SH subjects and controls at baseline and increased similarly over time, whereas SH children showed a significant prolongation of isovolumic relaxation time (IVRT) (85.95±2.72 msec) compared to controls (78.82±2.27 msec, P<0.05), even-though still within normal values for age. In the 22 SH children who underwent L-T4 therapy, the IVRT significantly decreased (74.61±3.25 msec) versus baseline value (85.47±2.89 msec, P<0.05) and became similar to controls (74.92±1.18 msec). No significant differences in HR, SBP and DBP were detected between SH subjects and controls.

Conclusions: Long lasting mild SH in children seems to be associated with mild subclinical diastolic dysfunction, which improved with L-T₄ therapy. Whether this subtle alteration may lead to clinical consequences should be further investigated.