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

We evaluated the stimulation of Chinese hamster ovary cells expressing huma n thyrotropin receptors (CHO-hTSHR cell) by sera of five patients with hyda tidiform mole before and after the evacuation of the mole, and compared the results with serum human chorionic gonadotropin (hCG) concentrations and s erum free thyroid hormones in these patients. Significantly increased CHO-h TSHR cell stimulating activities were observed in sera from untreated patie nts, 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 signific antly correlated with serum hCG. Moreover, serum hCG stimulated CHO-hTSHR c ells in a dose dependent manner similar to the dose-response curve of the s timulation by purified hCG. Sera of the patients and purified hCG did not s timulate nontransfected CHO-K1 cells. However, a significant correlation wa s not observed between serum-free thyroid hormones and serum hCG or between serum free thyroid hormones and CHO-hTSHR cell stimulating activities in u ntreated patients. These results indicate that serum hCG from patients with hydatidiform mole stimulates thyroid gland by interacting with TSH recepto rs, and suggest that the increase in thyroid hormones in patients may depen d on both the increased serum hCG and the responsiveness of their thyroid g lands to hCG.