Clinical presentation: A 24-year-old woman requested a second opinion. Levothyroxine therapy was initiated 9 months ago when Hashimoto's thyroiditis was diagnosed in euthyroid state (TSH 1.07 mIU/L).

Palpation: The thyroid was not palpable.

Hormonal investigation: euthyroidism on daily 50 microgram levo-tiroxine (TSH 1.09 mIU/L, FT4 15.3 pM/l, aTPO 93 U/mL).

Ultrasonography revealed an echonormal thyroid containing several small hypoechogenic areas. The echogenicity index was around 5%.

Diagnosis: Hashimoto's thyroiditis.

Suggestion: discontinuation of levo-tiroxine therapy. TSH-determination in a year and in the event of pregnancy at once.

Comment. On our opinion there is no reason to treat a euthyroid patient if the TSH is ideal, i.e. below 3 mIU/L in a woman in child-bearing age and if the thyroid is not enlarged.