[TSH-receptor antibodies in thyroid diseases]

The clinical usefulness of detection of TSH receptor antibodies (TRAK-assay, Henning) in differential diagnosis of thyroid disorders and in follow up of treatment of Graves' disease was evaluated and compared to thyroperoxidase antibodies estimation (DYNOtest antiTPO Henning). 313 patients with various thyroid diseases and 50 persons from control group were examined. Thyroperoxidase antibody (TPO-Ab) titers were frequently elevated in Graves' disease before treatment (88.6%, median 3361 U/ml) and in Hashimoto thyroiditis (100%, median 6055 U/ml). Median TPO-Ab was in normal range in other thyroid disorders and in control group (toxic nodular goiter: 58.5 U/ml, neutral nodular goiter: 46.0 U/ml, thyroid cancer after thyroidectomy: 58.8 U/ml, control group: 0 U/ml). TSH-receptor antibodies (TRAb) were detected in 94.1% in patients with Graves' disease (median 52 U/l) and only in 12.5% with Hashimoto disease (median 4.1 U/l), in 25% with toxic nodular goiter (median 4.1 U/l), in 10.9% with neutral nodular goiter (median 4.6 U/l) in 17.4% with thyroid cancer (median 1.6 U/l) and in 4.8% in control group (median 1.7 U/l). The TPO-Ab titers did not decrease significantly during thyrostatic treatment of Graves' disease. Patients in clinical remission after treatment exhibited TPO-Ab in 76.9% (median 615.5 U/ml). In contrast, the TRAb titers failed in patients treated with thyrostatics longer then six months (64%, median 16 U/l). After treatment 86.7% of them had normal values (median 1.0 U/l). The increase of TPO-Ab persisted in patients investigated two years after subtotal thyroidectomy (92.3%, median 750 U/ml). Only in patients operated before 10 years the titers declinedsignificantly (32%, median 43.4 U/ml). The TRAb titers fell significantly after thyroidectomy (two years: 62.5%, median 10.7% U/l, 10 years: 36.4%, median 4.2 U/l). Estimation of TRAb is a powerful tool for differential diagnosis of Graves' disease and enables better monitoring of the applied treatment than estimation of TPO-Ab.