Clinical presentation: an 21-year old man was referred for evaluation of a newly discovered hypothyroidism. He had fatigue, loss of hair and gained 5 kg in weight in the previous 6 month.

Palpation: the thyroid was not palpable.

Hormonal examination: hypothyroidism with TSH 11.9 mIU/L, FT4 8.01 pM/L.

Ultrasonography: an intact thyroid with echonormal structure and normal vascularization.

The patient denied ingesting any unknown drugs or foods with large iodine-content.

We repeated the blood test which resulted in euthyroidism: TSH 2.96 mIU/L, FT4 13.0 mIU/L, anti-TPO 0 U/mL, anti-hTg 0 U/mL.

Diagnosis: a healthy thyroid.

We offered checking the thyroid function in half a year. This test resulted again in euthyroidism (TSH 2.78 mIU/L).

Comment.

1. An overt hypothyroidism with an echonormal intact thyroid is a very rare finding. The cause for hypothyroidism in an adult patient is autoimmune thyroiditis in most if not all of the cases except for those patients who were operated on or treated with thyrostatic drug or radioiodine. An autoimmune thyroiditis presents a hypoechogenic pattern in more than 90% of cases. This ratio is even higher in overt hypothyroidism.

2. Only ten days have elapsed between the two blood tests with different results. It is hard to imagine such degree of spontaneous decrease in the TSH-level within such a short period. We suppose that the blood test tube of the patient was confused with the tube of a hypothyroid patient.