BACKGROUND: Hashimoto's thyroiditis is associated with a diffuse reduction in thyroid echo levels. The purpose of this study was to determine the degree of hypoechogenicity in correlation to clinical features and laboratory parameters. MATERIAL/METHODS: 52 patients with Hashimoto's thyroiditis under substitutive therapy with levothyroxine (50-200 g daily) and 100 normal euthyroid volunteers (with no features of autoimmune disease who were not taking any thyroid medication) as controls were investigated. Determination of plasma free thyroxine (FT4) and TSH as well as peroxidase- (TPO), thyroglobulin- and TSH receptor (TSH-R) antibodies were performed. Thyroid volume was measured by conventional ultrasonography. Tissue echogenicity was characterized by standardized grey scale ultrasonography under defined operating conditions. Mean densities were given in a histogram range of grey scales between 0-63 GWE (= Grauwerteinheiten). RESULTS: Patients with Hashimoto's thyroiditis revealed significantly lower echo levels (19.6+/-2.6 GWE) than controls (25.6+/-2.0 GWE, p<0.001). High graded hypoechogenicity was associated with large goiters, persistently increased TSH levels (subclinical hypothyroidism) and highly elevated TPO-antibodies. CONCLUSIONS: Standardized grey scale ultrasonography allows for reproducable correlations between functional status and morphological characteristics of the thyroid gland in Hashimoto's thyroiditis. The results hint at a stronger inflammatory process in higher grades of hypoechogenicity.

Keywords: Hypothyroidism - pathology, Receptors, Thyrotropin - blood, Thyroiditis, Autoimmune - drug therapy, Thyroiditis, Autoimmune - ultrasonography, Thyrotropin - blood, Thyroxine - blood