Abstract
In an attempt to provide better assessment of human chorionic gonadotropin Β-subunit (hCG-Β) secretion in pregnant women, a method was developed for complete removal of hCG by porcine-purified receptors before measurement of the free hCG-Β subunit by radioimmunoassay. Blood samples of 111 pregnant women were collected and the following results were obtained: (1) Extensive removal (over 96%) of hCG allows quantitative determination of the free hCG-Β subunit by a specific radioimmunoassay. Our data demonstrate the presence of circulating hCG-Β subunit during pregnancy, a fact that was still under controversy until now. (2) In contrast with the hCG profile during pregnancy the free hCG-Β subunit exhibits a plasma concentration peak (400 ± 132 ng/ml; mean ± 1 SD) at the 12th-13th week, indicating that the changes in plasma levels of intact hCG and free hCG-Β subunit are unrelated.