Clinical usefulness of thyroid-stimulating antibody measurement using Chinese hamster ovary cells expressing human thyrotropin receptors.

Human thyrotropin (TSH) receptors were expressed in Chinese hamster ovary (CHO) cells using eukaryotic expression plasmid pCXN2, which contains beta-actin promoter. We measured cAMP stimulation in CHO cells expressing human TSH receptors (CHO-hTSH-R cells) by immunoglobulin G (IgG) of patients with Graves' disease and Hashimoto's thyroiditis, and compared the results with a conventional thyroid-stimulating antibody (TS-Ab) assay using porcine thyroid cells and a TSH-binding inhibiting immunoglobulin (TBII) assay. Nineteen untreated patients with Graves' disease, including a case who developed hyperthyroidism after interferon -alpha therapy for chronic hepatitis C, and 13 treated patients with Graves' disease, 10 patients with Hashimoto's thyroiditis and 8 control subjects were studied. In 19 untreated patients with Graves' disease, 17 patients showed positive CHO-hTSH-R cell stimulation, 11 patients showed positive porcine thyroid cell stimulation and 15 patients showed positive TBII. All the untreated patients showed positive results in at least one assay. Although significantly positive correlations were observed among CHO-hTSH-R cell stimulation, porcine thyroid cell stimulation and TBII activities, the IgG of several patients showed significant discrepancy in the assay results. In a patient with interferon-induced hyperthyroidism only CHO-hTSH-R cell stimulation was positive, while porcine thyroid cell stimulation and TBII were negative. After the treatment with propylthiouracil for 6 months, CHO-hTSH-R cell stimulation became negative. The IgG of patients with Hashimoto's thyroiditis did not show significant stimulation of CHO-hTSH-R cells. These results suggest that the CHO-hTSH-R cell stimulation assay is clinically useful for the diagnosis and follow-up of patients with Graves' disease.