Clinical presentation: a 41-year-old man was referred for evaluation of suspected thyroiditis. He suffered from upper airways infection. Three weeks later the left thyroid became swollen and tender, the fever increased.

Palpation: the left thyroid was hard and not tender.

Functional state: subclinical hyperthyroidism with TSH-level 0.01 mIU/L, FT4 19.1 pM/L, FT3 4.08 pM/L.

Ultrasonography: there were multiple hypoechogenic areas with blurred borders within echonormal background. The vascularization was decreased.

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

Suggestion: steroid therapy.