Clinical data: A 60-year-old woman was referred for an evaluation of hyperthyroidism. She has been treated with Graves' disease for 11 years. Her complaints recurred 3 months before the present examination. She had thyroid associated orbitopathy including diplopia.

Palpation: diffusely enlarged thyroids.

Result of blood test: hyperthyroidism with TSH-level 0.001 mIU/L and FT4 71.8 pM/L.

Ultrasonography: A hypoechogenic, inhomogeneous thyroid was found with increased vascularization.

Clinical diagnosis: recurrent hyperthyroidism caused by Graves' disease.

Comment: daily 40 mg methimazole was administered. Two months later the FT4 level became normal. Surgery was advised because of TAO.

Histopathology: diffuse goiter corresponding to Graves' disease.