The natural history of the normal/mild elevated TSH serum levels in children and adolescents with Hashimoto's thyroiditis and isolated hyperthyrotropinaemia: a 3-year follow-up.

Objective:   The natural history of Hashimoto's thyroiditis (HT) and isolated hyperthyrotropinaemia (IH) is not well defined. We therefore studied the natural course of patients with HT and IH and looked for possible prognostic factors.

Design:   This is retrospective cross-sectional study.

Patients:   Three hundred and twenty-three patients with HT (88 boys and 235 girls) and 59 with IH (30 boys and 29 girls), mean age 9·9 ± 3·8 years were included in the study. When first examined, 236 of the children with HT had a normal TSH (G0) and in 87, it was elevated but <100% of the upper limit (G1). All IH subjects had elevated TSH. Potential risk factors for thyroid failure were evaluated after 3 years and included the presence or familiarity for endocrine/autoimmune diseases, premature birth, signs and symptoms of hypothyroidism, TSH levels, antithyroid antibodies and thyroid volume.

Results:   HT: Of those with HT, 170 G0 patients remained stable, 31 moved to G1 and 35 to G2 (hypothyroidism). Thirty-six G1 children moved to G0, 17 remained stable and 34 moved to G2. Of patients with IH: 23 normalized, 28 remained stable and eight became overtly hypothyroid. In patients with HT, the presence of coeliac disease, elevated TSH and thyroid peroxidase antibodies (TPOAb) increased the risk of developing hypothyroidism by 4·0-, 3·4- and 3·5-fold, respectively. The increase in TSH levels during follow-up was strongly predictive of the development of hypothyroidism. In patients with IH, no predictive factor could be identified.

Conclusions:   Coeliac disease, elevated TSH and TPOAb at presentation and a progressive increase in TSH are predictive factors for thyroid failure in HT patients.