Clinical presentation: A 37-year-old woman was referred for evaluation of complaints suggesting hyperthyroidism. She had partum thyroiditis twice, 5 and 3 years before the present visit. She has never got any thyroid medications.

Palpation. Both lobes were firm.

Laboratory test: TSH 0.04 mIU/L, FT4 16.8 pM/L, FT3 7.43 pM/L, TSAb 0.3 U/L (normal value < 5), aTPO 10 U/mL, ahTg 16 U/mL.

Ultrasonography. The thyroid was basically hypoechogenic. There were less and more hypoechogenic parts within. The thyroid presented proliferation of connective tissue. There were no pathological nodules.

Diagnosis: Hashitoxicosis. Beta-blocking agent was administered.

Follow-up. Six weeks later the patient became hypothyroid (TSH 11.3 mIU/L) while another 3 months later the thyroid functions returned spontaneously to normal level.