The presence of slightly high thyroid-stimulating hormone (TSH) with normal free T4 (FT4) serum concentrations in an asymptomatic individual is defined as subclinical hypothyroidism. The aim of this study was to evaluate the spontaneous course of thyroid activity in asymptomatic children who were found to have mild hyperthyrotropinaemia and who were not treated with l-thyroxine. 18 patients (9 female; 9 male) were divided into two groups: group A: five patients with hyperthyrotropinaemia found through neonatal screening; group B: 13 patients with hyperthyrotropinaemia found later in life (four: familiar history of hypothyroidism; one: obesity; three: growth impairment; five: unintentionally). The median age at diagnosis in group B was 4.7 years (0.5–11.3), and TSH values were between 6.2 and 21.6 μU/ml in both groups. TSH values and clinical evaluation were repeated more frequently in group A, with a median clinical and biochemical follow-up of 4.4 years in both groups (range 1–12). None of the patients developed clinical or biochemical signs of hypothyroidism. Whereas TSH values showed a fluctuating pattern, serum FT4 concentrations remained within the normal range at every control.
In conclusion, asymptomatic paediatric patients with normally positioned thyroid gland, slightly high serum TSH and normal FT4 concentrations do not usually require l-thyroxine therapy. Even TSH values as high as above 10 μU/m will only need close follow-up evaluation as the natural course of TSH value is unpredictable, with a possible spontaneous normalisation. Decreased FT4 concentrations, increased pathological response to thyrotrophin-releasing hormone provocation testing or symptoms of hypothyroidism are indications for commencing treatment.