are produced by many tumors. The hormone may be a natural product of
its associated organ or represent abnormal synthesis reflecting
unregulated cancer cell metabolism. Examples include insulin
production by islet cell tumor, calcitonin by medullary thyroid
carcinoma, and catecholamines by pheochromocytoma. Or it may be that
the hormone is not a natural product of its associated organ, in which
case is designated "ectopic". Examples include the
production of ACTH and ADH by lung cancers.
this section, discussion is limited to human chorionic gonadotropin.
Other hormones will be discussed in another review.
HCG is a
glycoprotein consisting of subunits a e b, which are nonconvalently
linked. The hormone is normally produced by the syncytiotrophoblastic
cells of the placenta and is elevated in pregnancy. Its most important
uses as a tumor marker are in gestational trophoblastic disease and
germ cell tumors.
trophoblastic tumors produce HCG, and it is a valuable marker in these
tumors, screening reliably in all cases and indicating poor responses
to treatment. The level correlates with tumor mass and thus has
prognostic value. HCG is extremely sensitive, being elevated in women
with minute amounts of tumor. The patient is followed weekly during
treatment, and at the completion of treatment indefinite follow up is
advised to detect recurrence. HCG is essential in managing
The level of HCG
is occasionally elevated in other cancers including those of breast,
lung, and gastrointestinal tract, but in these diseases it has found
little clinical application.