Context: The use of levothyroxine to reduce thyroid size in pediatric patients with goiter due to chronic autoimmune thyroiditis (AIT) remains controversial. In overtly hypothyroid patients, reductions in thyroid volume have been reported, while the effect in subclinically hypothyroid and euthyroid patients is less clear.

Objective: To evaluate the effect of levothyroxine treatment on thyroid size (determined with thyroid ultrasonography) in children and adolescents with AIT.

Design and setting: This study included patients with AIT treated at a university hospital outpatient clinic between 1987 and 2004.

Patients: Ninety children with AIT (73 girls and 17 boys, ages 6.1-17.7 yr).

Intervention: Treatment with levothyroxine for median 2.8 yr (range 0.5-10.2).

Main outcome measure: Change in thyroid volume SD score (SDS) during the study period.

Results: Median thyroid volume SDS was reduced in patients euthyroid (-0.4 SDS, P < 0.001), subclinically hypothyroid (-1.4 SDS, P < 0.001), and overtly hypothyroid (-1.8 SDS, P < 0.002) at diagnosis of AIT. Both hypothyroid and euthyroid patients with goiter (thyroid volume > 2.0 SDS) at baseline reduced their median thyroid volume SDS (-1.6 and -0.9, respectively, P < 0.001). Hypothyroid patients without goitre also reduced median thyroid volume SDS (-1.2, P < 0.004), while no change was noticed in euthyroid children without goiter.

Conclusions: Levothyroxine treatment is effective in reducing thyroid volume in pediatric patients and is suggested in treatment of goiter caused by AIT, especially in cases of hypothyroid, but also in euthyroid children.