Clinical data: a 22-year-old woman was referred for an evaluation of a hyperthyroidism. She suffered from typical complaints of hyperthyroidism for 6 weeks including elevated pulse rate (100/min) and 7 kg weight loss.

Palpation: no abnormality.

Results of blood tests: mild hyperthyroidism (TSH 0.01 mIU/L, FT4 27.4 pM/L, FT4 7.83 pM/L). TSAb 4.1 U/L (normal value < 1.5), aTPO 743 U/mL.

Ultrasonography: the thyroids were echonormal and contained moderately hypoechogenic areas. The echogenicity index was around 20%. The vascularization was not increased in the right while practically absent in the left lobe.

Cytology: was performed from the hypoechogenic lesion in the left lobe and resulted in benign lesion corresponding to Graves' disease.

We administered beta-blocking agent. 4 weeks later neither the complaints nor the hormonal status was changed and we administered daily 15 mg methimazole. The patient was treated for a year. Two months after the discontinuation of methimazole the hyperthyroidism recurred. Radioiodine therapy was performed.

Comment: It is rare that the vascularization is decreased in hyperthyroid phase of an active hormone-producing thyroid disease. Despite mild elevation of TSAb, hashitoxicosis had to be considered and therefore we performed cytology.