Stimulation of Chinese hamster ovary cells expressing human thyrotropin receptors by serum human chorionic gonadotropin of patients with hydatidiform mole.

We evaluated the stimulation of Chinese hamster ovary cells expressing human thyrotropin receptors (CHO-hTSHR cell) by sera of five patients with hydatidiform mole before and after the evacuation of the mole, and compared the results with serum human chorionic gonadotropin (hCG) concentrations and serum free thyroid hormones in these patients. Significantly increased CHO-hTSHR cell stimulating activities were observed in sera from untreated patients, and the activity decreased promptly after the evacuation of the mole, concomitantly with the decrease in serum hCG and free thyroid hormones. CHO-hTSHR cell stimulating activity of sera of the untreated patients significantly correlated with serum hCG. Moreover, serum hCG stimulated CHO-hTSHR cells in a dose dependent manner similar to the dose-response curve of the stimulation by purified hCG. Sera of the patients and purified hCG did not stimulate nontransfected CHO-K1 cells. However, a significant correlation was not observed between serum-free thyroid hormones and serum hCG or between serum free thyroid hormones and CHO-hTSHR cell stimulating activities in untreated patients. These results indicate that serum hCG from patients with hydatidiform mole stimulates thyroid gland by interacting with TSH receptors, and suggest that the increase in thyroid hormones in patients may depend on both the increased serum hCG and the responsiveness of their thyroid glands to hCG.