Clinical presentation: a 48-year-old woman with fever and painful thyroid lasting for a month. Both thyroids were hard and painful on palpation.

Functional state: hyperthyroidism with TSH-level 0.01 mIU/L, FT4 33.1 pM/L .

Ultrasonography: there were many hypoechogenic areas with blurred borders within both lobes. The vascularization was decreased.

Cytological diagnosis: subacute, granulomatous de Quervain's thyroiditis.

Suggestion: steroid therapy.