Clinical presentation: a 49-year-old woman was treated with methimazole three month prior to the present visit. Two weeks after administration of thyrostatic drug severe hypothyroidism developed. The methimazole was stopped. The complaints of the patient recurred.

Palpation: no abnormality.

Results of blood tests: hyperthyroidism with undetectable TSH-level. FT4 was 38.1 pM/L. TsAB-assay 7.1 U/L (normal value under 1.5), aTPO 773 U/mL.

Ultrasonography: a diffusely hypoechogenic thyroid was found with increased vascularization.

Cytological picture: benign, corresponding to Graves' disease.

Comment: the indication of aspiration cytology may be questioned, but FNAC may have practical value in such circumstances. Despite the elevated TsAB level, Hashitoxicosis cannot be excluded. See section Hashimoto's thyroiditis Case 55.