A levothyroxine dose recommendation for the treatment of children and adolescents with autoimmune thyroiditis induced hypothyroidism.

OBJECTIVE To determine a levothyroxine (T4) dose recommendation for the treatment of autoimmune thyroiditis (AIT)-induced hypothyroidism. METHODS T4 doses in 75 children and adolescents with newly diagnosed AIT were prospectively collected and compared to T4 doses of patients with congenital hypothyroidism (CH, n=22). RESULTS Sixty-four patients with AIT and 22 patients with CH were included in the analysis. The thyroid-stimulating hormone declined significantly from 25.8 ± 50.1 to 2.1 ± 1.5 μIU/mL (AIT group; p<0.01) and from 338.7 ± 380.7 to 1.9 ± 1.6 μIU/mL (CH group; p<0.01). The required T4 dose for patients with AIT was 1.5 ± 0.5 μg/kg per day (≥ 6 to <10 years: 2.0 ± 0.4 μg T4/kg per day; ≥ 10 to <12 years: 1.6 ± 0.4 μg T4/kg per day; ≥ 12 to <14 years: 1.5 ± 0.6 μg T4/kg per day; ≥ 14 years: 1.4 ± 0.6 μg T4/kg per day). It deviated significantly from the CH patients' mean T4 dose of 2.8 ± 0.7 μg T4/kg per day, p<0.01. CH patients with athyreosis required an average dose of 3.1 ± 0.5 μg T4/kg per day; patients with ectopia, 2.6 ± 0.7 μg T4/kg per day; and patients with dyshormonogenesis, 2.5 ± 0.6 μg T4/kg per day. CONCLUSION Juvenile patients with AIT require significantly lower T4 doses than patients with CH.