Clinical presentation: a 46-year-old woman with fever and painful thyroid which had been present for 3 weeks. She suffered upper airways infection 3 months earlier. Both thyroids were hard and painful on palpation.

Functional state: hyperthyroidism with TSH-level 0.01 mIU/L, FT4 38.7 pM/L, ESR 52 mm/H, CRP 29.0 mg/L.

Ultrasonography: diffusely moderately hypoechogenic lobes with several circumscribed, even more hypoechogenic areas with blurred borders.

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

Suggestion: steroid therapy.