Hyperglycosylated hCG, a review.

Hyperglycosylated hCG (hCG-H) is a glycoprotein with the same polypeptide structure as hCG, and much larger N- and O-linked oligosaccharides. The oligosaccharides increase the molecular weight of hCG from 36,000 - 37,000 u to 40,000 - 41,000 u, depending on the extent of hyperglycosylation. hCG-H has triantennary N-linked oligosaccharides and double molecular size O-linked oligosaccharides (hexasaccharide compared with predominantly trisaccharide structures). hCG is produced by syncytiotrophoblast cells while hCG-H is made by extravillous cytotrophoblast cells. hCG-H promotes trophoblast invasion during choriocarcinoma, growth of cytotrophoblast cells and placental implantation in pregnancy. hCG-H is an independent molecule to hCG with totally separate biological functions. hCG has numerous functions during pregnancy, it promotes progesterone production, promotes angiogenesis in uterine vasculature, immuno-suppresses the invading placental tissue, promotes the growth of the uterus in line with the growth of the fetus during pregnancy, promotes the differentiation of growing cytotrophoblast cells, promotes the quiescence of contractions in the uterine myometrium during the course of pregnancy, and also has function in growth and development of fetal organs. Monoclonal antibody B152 uniquely binds hCG-H. Using this monoclonal antibody in immunometric assays permits detection of pregnancy. It also permits management of gestational trophoblastic diseases and detection of quiescent gestational trophoblastic disease. This same test can be used to differentiate of aggressive and minimally-aggressive gestational trophoblastic disease, and discrimination of patients that respond to chemotherapy and who are chemorefractory. The hCG-H test can be used to screen for Down syndrome pregnancies and predict patients likely to generate hypertensive disorder in pregnancy. It also can be used to differentiate pregnancies that will miscarry and pregnancies that will go to term.