Serum human chorionic gonadotropin (hCG) was measured by a radioreceptorassay (RRA) and radioimmunoassay (RIA) and serum hCG-β and hCG-α by RIA in 10 patients with intact mole, 3 patients with choriocarcinoma, and 4 patients with hydatidiform mole during treatment. hCG levels by RRA were higher in 5 of 10 molar pregnancies and ranged from 20,900 to 100,000 ng/ml and from 30,000 to 100,000 ng/ml by RIA. hCG levels by RRA and RIA paralleled one another closely during treatment of hydatidiform mole. hCG-α was higher than hCG by RRA and RIA and hCG-β in molar pregnancies, in the uterine venous blood draining a uterine choriocarcinoma, and during chemotherapy of choriocarcinoma. In 2 of 3 choriocarcinoma patients who eventually developed cerebral metastases, hCG-α increased while hCG and hCG-β were declining or negative. hCG-β was usually lower than hCG or hCG-α in all the cases studied. These results demonstrate the production of free α and β subunits in trophoblastic disease. Further, due to the biospecificity, simplicity, and rapidity, the RRA of hCG is a useful diagnostic aid during treatment of trophoblastic neoplasia until the levels fall to within the sensitivity range of the assay. Finally, the RIA of hCG, hCG-β, and hCG-α, which requires several days, should be performed until they become negative or fall within normal range
