[Modern diagnostic approach to autoimmune thyroiditis].

High-resolution ultrasonography of the thyroid gland is the major primarytechnical diagnostic procedure in suspected autoimmune thyroiditis (AIT). A diffusely echo-poor thyroid is proof of the presence of AIT. Duplex sonography provides further information about the activity of the disease, and is of differential diagnostic importance for distinguishing postpartum thyroiditis from AIT, or for the investigation of an infiltrating carcinoma. Today, antibody determination serves merely to confirm the diagnosis, with TPO antibodies being the most specific for AIT. The TG antibodies may also be nonspecifically elevated in subacute thyroiditis (de Quervain) or irradiation or radioiodine treatment. For an evaluation of thyroid gland function in AIT, determination of basal TSH is needed.