First examination (first and second rows of images):

Clinical presentation: a 33-year-old woman was referred for an evaluation of complaints suggesting hyperthyroidism. The patient was never pregnant.

Palpation: no abnormality.

Results of blood tests indicated moderate degree of hyperthyroidism (TSH undetectable, FT4 31.0 pM/L), aTPO 703 U/mL, TSAb 0.5 U/L (normal value < 1.5).

Ultrasonography: a diffusely hypoechogenic thyroid was found with several discrete lesions. The vascularization was increased.

Cytology: was performed from the right lobe.

Cytological diagnosis: benign pattern corresponding to hyperthyroidism without any signs of thyroiditis.

Considering the results of investigation, low dose (daily 15 mg) methimazole was administered.

Follow-up examination 15 months after first visit (second and third rows):

Clinical presentation: the patient was regularly followed-up and was euthyroid on daily 10 mg methimazole. She had no complaints.

Palpation: no abnormality.

Results of blood tests: euthyroidism on daily 10 mg methimazole (TSH 1.83 mIU/L, FT4 14.6 pM/L).

Ultrasonography: the thyroids were echonormal and contained small punctate hypoechogenic areas. The vascularization was practically absent.

The thyrostatic was discontinued.

Comments.

1. The patient had a typical presentation of hashitoxicosis including elevated aTPO and normal TSAb levels and moderate degree of hyperthyroidism. However, there were two circumstances arguing against thyroiditis: the extremely increased vascularization and the cytologic pattern.

2. The sensitivity of TSAb is around 90% in our practice. This patient belonged to the 10% of false negative cases.