Free Beta hCG

The Human Chorionic Gonadotropin (HCG) is one of
the most important protein involved in pregnancy.
HCG is secreted by placental tissue and serves to
support the corpus luteum during the early weeks of
pregnancy; so HCG concentration increases in blood
and urine during normal pregnancy.
The concentration of HCG is a marker for the
detection of pregnancy and the potential diagnosis of
early pregnancy disorders. Free -HCG subunit
testing has improved the diagnostic probability of
abnormal pregnancy/disease states.
In case of trophoblastic disease, many irregular forms
of HCG are produced, such as nicked HCG, HCG
missing the -subunit C-terminal fragment,
hyperglycosylated HCG and free -subunit. Also,
common epithelial tumors of the urogenital tract
frequently express the free -subunit of HCG without
the concomitant expression of the -subunit; other
studies regarding ovarian tumors, epithelial tumors
and trophoblastic malfunctions show the necessity to
have a differential diagnosis based on the
determination of specific proteins involved such as
HCG, free -HCG, nicked HCG and the different
subunits.
Free -HCG is 26% of total HCG in trophoblast
disease (while in normal conditions it is 1%). There is
also increasing evidence that free -subunit may be
better that total HCG determination in assessing
Down's Syndrome.