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Human Chorionic Gonadotropin Tumor Marker

Measurement of serum hCG concentration is useful in evaluating and monitoring trophoblastic disease. Choriocarcinoma occurs in 5 to 10% of women who have a pregnancy associated with a hydatidiform mole. Serum hCG levels are monitored during follow-up after evacuation of hydatidiform mole.These tumors excrete large amounts of hCG (100,000 mIU/mL) and the hormone levels do not decrease as in normal pregnancy but exhibit irregular fluctuations. Because the half‑life of hCG is 24 hours, levels may remain detectable for days following surgical removal. HCG becomes nondetectable within 8 weeks in 40% of patients, between 9 and 22 weeks in 55% of patients and in >22 weeks in 5%. If hCG returns to normal at a later date, a two year follow-up is required to rule out choriocarcinoma. Rising hCG levels at any time indicate cancer. hCG is a very sensitive marker for early choriocarcinoma and can detect tumors weighing only 1 mg. Monitoring hCG levels after detection of a hydatidiform mole has drastically reduced the death rate from trophoblastic tumors.

Most testicular cancers are germ cell tumors; including 50% seminomas and 50% nonseminomas. The latter group is subclassified into embryonal carcinoma, choriocarcinoma, yolk sac tumors and teratomas. Clinical guidelines for evaluation of testicular germ cell tumors include measurement of alpha fetoprotein (AFP) and human chorionic gonadotropin.

Seminomas produce a mixture of hyperglycosylated hCG and hCG beta core fragment. Nonseminomatous germ cell tumors produce mixture of nicked hCG, hyperglycosylated hCG and hCG beta core fragment. Different hCG assays vary in their ability to detect all forms of hCG secreted by tumors. The hCG assay used as a tumor marker should ideally have equimolar detection of intact hCG and hCG beta core fragment. These assays are commonly referred to as total hCG immunoassays. When monitoring patients, the same assay should be used because of high interassay variability.

Elevated hCG levels may also be seen in patients with, multiple pregnancy, polyhydramnios, eclampsia, erythroblastosis fetalis and several non‑trophoblastic tumors (i.e. breast, hepatic, renal, adrenal, bronchogenic, pancreatic and gastrointestinal carcinomas, and leukemia, lymphoma and myeloma).

Heterophile antibodies may produce falsely elevated serum hCG results. Heterophile antibodies are human antibodies with specificity for animal antibodies used in immunoassays for hCG. A three prong approach can be used to rule out the presence of falsely elevated hCG due to heterophilic antibodies.

  • Perform a urine pregnancy test because heterophilic antibodies are not present in urine.
  • Measure hCG on serial dilutions of serum.
  • Preabsorb serum to remove heterophilic antibodies.

Specimen requirement is one SST tube of blood.

Serum hCG reference range is:

Female, premenopausal 0 - 5 mIU/mL
Female, perimenopausal 0 – 15 mIU/mL
Male 0 - 5 mIU/mL
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