The circulating alpha subunit of human chorionic gonadotrophin in gynacologic tumours

The circulating levels of the immunoreactive alpha subunit of glycoprotein hormones were measured by the hCG alpha subunit radioimmunoassay in 101 patients with non‐trophoblastic gynaecological cancer and in 164 serum samples obtained from 10 patients with choriocarcinoma and five patients with hydatidiform mole. Serum samples from six patients with choriocarcinoma and four with hydatidiform mole were further examined for the existence of free alpha by chromatography on a calibrated Sephadex G‐100 column. In patients with non‐trophoblastic cancer the immunoreactive alpha subunit levels were not different from those of controls in the corresponding age groups. In trophoblastic disease all hCG‐positive samples showed also alpha subunit immunoreactivity when tested by radioimmunoassay, but no isolated alpha elevation was found. Chromatographic analyses revealed free alpha subunits in three out of six patients with choriocarcinoma and two out of four patients with hydatidiform mole. A patient who eventually died of choriocarcinoma was carefully followed for the free alpha secretion, and no alpha elevation was found in any of the 16 serum samples taken at various phases of disease. The present study shows that, unlike pancreatic islet cell tumours in vivo and HeLa cells in vitro, non‐trophoblastic gynaecologic cancer in vivo does not appear to have any significant alpha secretion. In trophoblastic disease free alpha subunits may coexist with native hCG more frequently than it was originally assumed, but no isolated alpha secretion could be demonstrated. The intriguing disparity between the alpha secretion by normal and abnormal trophoblasts was confirmed in this study, but the biological basis and significance of this phenomenon remain obscure.