Comparative evaluation of therapy with L-thyroxine versus no treatment in children with idiopathic and mild subclinical hypothyroidism

Objective: a) To evaluate auxological changes under L-T4 therapy and post-therapy evolution of thyroid function in 69 children with mild and “idiopathic” subclinical hypothyroidism SH (Group A); b) to compare our results with those recorded in 92 SH untreated children (Group B). Design: Group A children were treated for 24 months and their TSH and FT4 levels 3 months after therapy withdrawal (27 months) were compared with those measured in untreated Group B at the end of a 24-month follow-up. Results: The prevalence of children who normalized TSH values at the end of follow-up was significantly higher in Group A, but the overall prevalence of the ones who either normalized or maintained unchanged TSH levels was very similar in the 2 groups, as well as that of children who exhibited a further TSH increase above 10 mU/l. In Group A TSH values at 27 months were positively associated with the baseline ones. In both groups no significant clinical and auxological changes were observed during follow-up. Conclusions: a) a two-year treatment with L-T4 in children with “idiopathic” and mild SH is not able to distinctly modify the natural course of SH, at least in terms of growth and post-therapy outcome of hyperthyrotropinemia; b) therapy is not able to prevent the risk of a further increase of TSH after treatment withdrawal; c) post-therapy outcome of TSH serum levels is significantly conditioned by baseline TSH.