Graves' disease, the main cause of hyperthyroidism in the pediatric age group, is very rare in children younger than 4 years old but can seriously interfere with growth and development if not recognized and treated. Here we report a case of a 3-year-old girl with Graves' disease who presented with goiter, exophthalmos, heat intolerance, and hyperactivity. At her first visit, her serum concentrations of triiodothyronine (T3) and free thyroxine (free T4) were normal, whereas that of thyroid-stimulating hormone (TSH) was decreased. Antimicrosomal antibody was 7,053.94 IU/mL, and TSH-binding inhibitory immunoglobulin was 31.62%. A thyroid scan showed diffuse enlargement with markedly increased uptake of both thyroid glands. Although T3 and free T4 levels were initially normal, she developed hyperthyroidism 3 months later. She was finally diagnosed with Graves' disease and treated with methimazole for 6 months. This is the first report of Graves' disease in children younger than 4 years old in Korea.
Keywords: Child; Graves' disease; Hyperthyroidism.