Endocrine disorders in childhood and adolescence. Natural history of subclinical hypothyroidism in children and adolescents and potential effects of replacement therapy: a review.

OBJECTIVE: Subclinical hypothyroidism (SH) is quite common in children and adolescents. The natural history of this condition and the potential effects of replacement therapy need to be known to properly manage SH. The aim of this review is to analyse: 1) the spontaneous evolution of SH, in terms of the rate of reversion to euthyroidism the persistence of SH or the progression to over hypothyroidism; 2) the effects of replacement therapy, with respects to auxological data, thyroid volume and neuropsychological functions. Methods: We systematically searched PubMed, Cochrane and EMBASE (1990 to 2012) and identified 39 potentially relevant articles of which only 15 articles were suitable to be included. Results and Conclusions: SH in children is a remitting process with a low risk of evolution toward overt hypothyroidism. Most of the subjects reverted to euthyroidism or remained SH, with a rate of evolution toward overt hypothyroidism ranging between 0% to 28.8%, being 50% in only one study (9 articles). The initial presence of goiter and elevated thyroglobulin-antibodies, the presence of coeliac disease and a progressive increase in thyroperoxidase-antibodies and TSH value predict a progression toward overt hypothyroidism. Replacement therapy is not justified in children with SH but with TSH 5-10 mIU/L, no goiter and negative anti-thyroid antibodies. An increased growth velocity was shown in children treated with levothyroxine (2 articles). Levothyroxine reduced thyroid volume in 25% to 100% of children with SH and autoimmune thyroiditis (2 studies). No effects on neuropsychological functions (one study) and post-treatment evolution of SH (one study) were reported.