Clinical presentation: A 46-year-old woman was referred for evaluation of thyroid nodule. She has been treated for hypothyroidism for seven years.

Palpation. No abnormality.

Laboratory test: TSH 0.009 mIU/L, FT4 20.5 pM/L on daily 125 microgram levothyroxine. The aTPO level was 387 U/ml at the beginning of replacement therapy.

Ultrasonography. The thyroid was hypoechogenic and had numerous discrete areas. One of them located in the middle third of the right lobe might be a pathological nodule.

Aspiration cytology resulted in Hashimoto's thyroiditis.

Suggestion. The dose of the levothyroxine was decreased to daily 100 microgram.

Comment. The origin of the lesion in question is doubtful.