[Incidental finding: elevated TSH level].

The use of thyroid-stimulating hormone (TSH) testing in routine laboratory screening and testing of TSH before administration of contrast medium, resulted in an increased number of incidentally detected elevated TSH levels. In the case of slightly increased values in asymptomatic patients, repeated measurement of TSH is recommended for confirmation. Confirmed elevated TSH levels should lead to additional measurements of the peripheral thyroid hormones, determination of thyroid autoantibodies and performance of thyroid gland ultrasound examination. The most common reasons for acquired subclinical and overt hypothyroidism are autoimmune diseases of the thyroid gland and in many cases substitution therapy with levothyroxine is then necessary. In subclinical hypothyroidism it remains unclear at which TSH levels the initiation of substitution therapy makes sense. In the case of simultaneously elevated peripheral thyroid hormones rare diseases, such as secondary hyperthyroidism and thyroid hormone resistance should be considered.