ESPE Abstracts

Introduction: Hyperthyroidism (HT) is a condition characterized by inappropriately high thyroid hormone (TH) activity at receptor level, due to high synthesis and secretion of TH by thyroid gland. Antithyroid drugs as methimazole (MMI) are used as the first-line therapy in children. However, the optimal treatment duration and the predictive remission factors are still controversial.

Objective: To investigate outcome of MMI treatment and remission rate, and to identify associated remission factors in a group of HT children.

Material and methods: Sixty two patients (F:52 M:10), receiving MMI treatment and followed-up at least for 2 years, were included. Only children with adequate compliance were evaluated up to 5 years. Age, TSH, FT4 and T3 levels, MMI dose and thyroid gland ultrasound were analyzed at start of treatment in order to identify associated remission factors. Remission rate was evaluated at 2, 3 and 5 years in patients with adequate compliance. Remission was defined as a euthyroid state for at least 12 months after discontinuation of MMI treatment. Statistical analysis: R version 4.2.2. Mann-Whitney/T test and Fisher’s exact test to evaluate differences between groups.

Results: Median age at start treatment was 11.2 (7.7;12.9) years. Median MMI dose was 0.67 (0.53;0.86) mg/kg/day. Thyroid ultrasound (n=52) was normal in 4 (7.7%) patients. Twenty nine (55.8%) had heterogeneous gland, twelve children had goiter (23%) and seven had thyroid cystic or nodule (13.5%). At diagnosis, median TSH was 0.03 (0.01;0.06) uU/ml, mean FT4 was 4.20 ± 1.55 ng/dl and mean T3 was 506.97 ± 160.13 ng/dl. Remission was successfully achieved at a median time of 1.53 (0.60;2.45) years. Remission rate increased with treatment duration. It was 27.4% (n=17) in the total group at 2 years, 38% (n=19) in the 50 children followed-up to 3 years, and 65.8% (n=25) in the 38 patients with adequate compliance during 5 years. No significant differences were found between remission and non-remission patients at 2 years in the analyzed parameters at start of treatment.

Conclusion: Long-term MMI treatment is a useful option in children with hyperthyroidism. A longer MMI course was associated with a greater chance of remission in this population. Associated remission factors at start of treatment could not be identified.