Clinical presentation: A 31-year-old woman was referred for follow-up investigation. She suffered from a post partum thyroiditis 7 years ago. In the past seven years the TSH fluctuated between 0.9 and 5.8 mIU/l. We did not give replacement therapy because she had no complaints and there was no tendency in the change of TSH level.

Palpation: The thyroid was not palpable.

Hormonal investigation: euthyroidism (TSH 0.61 mIU/L, aTPO 0.4 U/mL).

Ultrasonography revealed a partly minimally hypoechogenic, partly echonormal thyroid. There was a small cystic lesion in the central part of the left lobe.

Suggestion. TSH in every two years, in the event of pregnancy at once.

Comment. If an adult woman has no complaints and does not wish to be pregnant in the near future, we do not give replacement therapy until the TSH is below 5 mIU/L or 7 mIU/L, before or after childbearing age, respectively. Usually, we administer replacement therapy if the TSH exceeds in two consecutive check-ups 3 mIU/L or 5 mIU/L, before and after the childbearing age except for patients without any laboratory and ultrasound signs of an underlying autoimmune thyroiditis when the threshold is 4 and 6 mIU/L instead of 3 and 5 mIU/L, before and after childbearing age, respectively.