[99mTc uptake and TSH receptor autoantibodies--comparative study in Basedow's disease and other thyroid diseases].

In 255 patients (normals: group I, n = 30; nontoxic goitres: group II, n = 134; toxic goitres without ophthalmopathy: group III, n = 63; Graves' disease: group IV, n = 28) a TSH-receptor-autoantibody-assay (TRAK assay) for detection of thyrotropin-binding inhibiting antibodies (TBIAb) was tested and 99mTcO4-uptake (TcTU) was measured. Normal TcTU (range: 1.5-5.5%) and normal TRAK values (normal limit: F less than 11%) were only found in group I. An increased TcTU was found in group II in 22.4% (increased TRAK values only in 2.2%). In group III an increased TcTU was measured in 34.9% of the patients (all with normal TRAK titers). The stimulation of the TSH-receptor in immunogenic hyperthyroidism by TBIAb could be demonstrated by increased TRAK values in 71.4% of the patients with Graves' disease. In correlation, TcTU was also increased in 82.1% of the patients in group IV. As the measurement of TcTU can be helpful in differential diagnosis, the functional imaging with gamma camera and computer is today a conditio sine qua non, especially in suspected hyperthyroidism.