Physiology, Chorionic Gonadotropin

Excerpt

The human chorionic gonadotropin (hCG) is recognized as a term to describe four separate isoforms, each with a distinct biological function and produced by a different type of cell within the body. These include synthesis from villous syncytiotrophoblasts, multiple primary non-trophoblastic malignancies or tumors, the anterior pituitary gland, and cytotrophoblast cells. The principal functions of hCG synthesized from villous syncytiotrophoblastic cells include promoting progesterone production by the corpus luteal cells and subsequent growth of cytotrophoblast cells. The actions of hCG allow a coordinated growth of the fetus and uterus, signals the endometrium of impending implantation, supports the growth and differentiation of the umbilical cord, as well as promotes fetal growth and organogenesis.

Hyperglycosylated forms of hCG from cytotrophoblastic cells promote growth and invasion of these cells, thus contributing to the pathogenesis of choriocarcinoma cells. A similar mechanism can occur in hCG free beta-subunits synthesized by non-trophoblastic tumors. The detection of the free-beta subunit hCG is suggestive of malign cancer and poor prognosis. hCG synthesized by the anterior pituitary gland is produced at low levels throughout the menstrual cycle and mimics the effects of the luteinizing hormone (LH).