BACKGROUND: hCG is a term referring to 4 independent molecules, each produced by 
separate cells and each having completely separate functions. These are hCG 
produced by villous syncytiotrophoblast cells, hyperglycosylated hCG produced by 
cytotrophoblast cells, free beta-subunit made by multiple primary 
non-trophoblastic malignancies, and pituitary hCG made by the gonadotrope cells 
of the anterior pituitary.
RESULTS AND DISCUSSION: hCG has numerous functions. hCG promotes progesterone 
production by corpus luteal cells; promotes angiogenesis in uterine vasculature; 
promoted the fusion of cytotrophoblast cell and differentiation to make 
syncytiotrophoblast cells; causes the blockage of any immune or macrophage 
action by mother on foreign invading placental cells; causes uterine growth 
parallel to fetal growth; suppresses any myometrial contractions during the 
course of pregnancy; causes growth and differentiation of the umbilical cord; 
signals the endometrium about forthcoming implantation; acts on receptor in 
mother's brain causing hyperemesis gravidarum, and seemingly promotes growth of 
fetal organs during pregnancy. Hyperglycosylated hCG functions to promote growth 
of cytotrophoblast cells and invasion by these cells, as occurs in implantation 
of pregnancy, and growth and invasion by choriocarcinoma cells. hCG free 
beta-subunit is produced by numerous non-trophoblastic malignancies of different 
primaries. The detection of free beta-subunit in these malignancies is generally 
considered a sign of poor prognosis. The free beta-subunit blocks apoptosis in 
cancer cells and promotes the growth and malignancy of the cancer. Pituitary hCG 
is a sulfated variant of hCG produced at low levels during the menstrual cycle. 
Pituitary hCG seems to mimic luteinizing hormone actions during the menstrual 
cycle.