Clinical data: a 38-year-old pregnant woman was referred for an evaluation of a thyroid nodule discovered on a routine examination. She got replacement therapy for hypothyroidism detected on the 5th gestational week. A nodule was described in the left lobe on ultrasonography.

Palpation: both thyroids were moderately firm. There was no palpable nodule.

Result of blood tests: euthyroidism on daily 50 microgram levothyroxine with TSH-level 3.91 mIU/L, FT4 12.1 pM/L.

Ultrasonography: the thyroid was minimally hypoechogenic. There was a small hypoechogenic lesion in the left lobe with the dimensions of 8x7x8 mm.

Cytological diagnosis: Hashimoto's thyroiditis.