Elevated TSH levels normalize or remain unchanged in the majority of children with subclinical hypothyroidism

SUMMARY BACKGROUND Subclinical hypothyroidism (SCH) is not very common during childhood and adolescence. Although data concerning the natural evolution of this disorder in children and adolescents is very sparse, some studies find that juvenile SCH may be a benign remitting process with a very low risk for progression to overt hypothyroidism. The aim of this study was to prospectively evaluate the course of SCH in children and adolescents with no underlying diseases and no risk factors that might interfere with the progression of SCH. METHODS This is a 2-year multicenter study that prospectively evaluated the spontaneous changes in thyrotropin (TSH) and free thyroxine (FT4) in a pediatric population comprising patients with idiopathic SCH without other nonthyroidal diseases and with no thyroid disorders or medications affecting the thyroid gland. The study subjects were children referred by community physicians because of an incidental finding of an elevated serum TSH concentration that was discovered during an annual checkup that included TSH measurement. SCH was defined as an elevated serum TSH level of 5 to 10 µIU/ml with a normal serum FT4 concentration of 10.3 to 24.4 pmol/L, both of which were measured twice over a 1- to 2-month interval as a requirement for admission into the study. In addition, patients were screened for thyroid immune disorders with anti-thyroid peroxidase antibodies (TPOAb) and by thyroid ultrasonography performed by the same operator at entry and at the end of the 24-month study. None of the children were taking drugs known to interfere with thyroid function or had prior head or neck radiation or a prior false positive screen for congenital hypothyroidism. The study was performed in non-iodine-deficient areas. All the children with idiopathic SCH were studied as outpatients, and after the initial