Differential production of human chorionic gonadotropin and free subunits in gestational trophoblastic disease

Serum levels of human chorionic gonadotropin (hCG) and its free subunits (alpha hCG and beta hCG) were determined by means of highly sensitive and specific monoclonal and antipeptide-based monoclonal immunoradiometric assays. During normal pregnancy, the beta hCG to hCG ratio appears constant at approximately 0.5% after 5 weeks of gestation. In contrast, gestational choriocarcinoma was characterized by absolute serum beta hCG levels varying from three to 280 times greater than the maximum values observed during pregnancy and by exceedingly high beta hCG to hCG ratios. In complete hydatidiform mole, this ratio was intermediate between normal pregnancy and choriocarcinoma. The ratios of free beta hCG to hCG will distinguish normal from complete molar pregnancy (p less than 10(-8)), hydatidiform mole from choriocarcinoma (p less than 10(-4)), and choriocarcinoma from normal pregnancy (p less than 10(-8)) with high probability. Finally, it was found by means of the high sensitivity hCG immunoradiometric assays (less than 0.02 ng/ml) that this assay predicted very early tumor recurrence in patients with gestational choriocarcinoma.