b-HCG ELISA

Human chorionic gonadotropin (HCG) is a
glycoprotein hormone secreted in pregnancy, that is
made by the embryo soon after conception and later
by the syncytiotrophoblast (part of the placenta). Its
role is to prevent the disintegration of the corpus
luteum of the ovary and thereby maintain
progesterone production that is critical for a
pregnancy in humans. HCG may have additional
functions, for instance it is thought that it affects the
immune tolerance of the pregnancy.
Pregnancy tests measure the levels of HCG in the
blood or urine to indicate the presence or absence of
an implanted embryo. In particular, pregnancy tests
employ an antibody that is specific to the β-subunit of
HCG (β-HCG). This is important so that tests do not
make false positives by confusing HCG with LH and
FSH.
β-HCG is also secreted by some cancers including
teratomas and choriocarcinomas. But, elevated levels
cannot prove the presence of a tumor, and low levels
do not rule it out.