hCG Tumor Marker
When your symptoms suggest gestational trophoblastic disease or germ cell tumors; to evaluate the effectiveness of treatment for these conditions; to monitor for recurrence
A blood sample drawn from a vein
Human chorionic gonadotropin (hCG) is a hormone, made up of an alpha and beta subunit, that is produced by the placenta and normally is only measurable during pregnancy. Some abnormal tissues, tumors, and cancers, however, may also produce hCG, making the hCG test useful as a tumor marker. This test measures the amount of intact hCG, and sometimes the beta subunit of hCG, in the blood.
An increased level of hCG is seen with gestational trophoblastic disease and some germ cell tumors (benign and cancerous). If hCG is increased with these conditions, then the hCG test can be used as a diagnostic and monitoring tool.
Gestational trophoblastic disease (GTD) is a group of tumor types that develop in a woman's uterus from the layer of cells surrounding an embryo that creates the placenta during a normal pregnancy (trophoblasts) and produces hCG. GTD usually occurs at the beginning of pregnancy after an egg has been fertilized, but instead of supporting the growth of a fetus, the cells form abnormal tissue masses. In most cases, the tumors are benign, but in a small percentage of people, they are cancerous. According to the American Cancer Society, GTD occurs in about 1 in 1,000 pregnancies. It can also occur after a normal pregnancy or after a miscarriage or abortion. The primary forms of GTD are:
- Hydatidiform mole – also called a "molar pregnancy," which may be complete (only tumor tissue) or a mixture of tumor and fetal tissue but does not develop into a viable baby; these are usually benign but must be surgically removed.
- Invasive mole – a hydatidiform mole that grows into the uterus wall; it must be surgically removed; however, the condition can persist if GTD tissue remains.
- Choriocarcinoma – a rare cancer that may develop from the GTD tumor tissue in about 2 to 7 per 100,000 pregnancies; these cancers can grow quickly and spread to other parts of the body.
- Placental site trophoblastic tumor – also rare, this tumor arises at the site of placental attachment in the uterus. This tumor usually develops after a normal or aborted pregnancy but doesn't often spread through the body.
- Epithelioid trophoblastic tumor – extremely rare, this tumor is similar in nature to the choriocarcinoma but is now considered a separate disease. It may take many years after a pregnancy for this tumor to be detected and may have already spread to other parts of the body.
Note: With appropriate treatment, the cure rate for most GTD is very high. For more on this, see the links in the Related Content section below.
Germ cell tumors and cancers occur primarily in the ovaries and testicles but can also rarely develop in other locations such as the chest.
- Germ cell tumors can occur in the egg-producing cells of the ovaries and are more often seen in younger women (for more, see Ovarian Cancer).
- Germ cell tumors can affect cells within the testicles that make sperm and account for more than 90% of testicular cancers (for more, see Testicular Cancer).
Levels of hCG may also be elevated in other diseases such as liver, breast, lung, skin, and stomach cancers. Increased levels may also be seen in non-cancer conditions such as cirrhosis, duodenal ulcer, and inflammatory bowel disease.
How is it used?
Quantitative human chorionic gonadotropin (hCG) testing, often called beta hCG (βhCG), measures the amount of hCG present in the blood. It may be used to help diagnose gestational trophoblastic disease (GTD) or, with other tests such as AFP and lactate dehydrogenase, to help diagnose germ cell tumors.
Since hCG is not normally present in men or non-pregnant women, it is useful as a tumor marker. If the tumor or cancer is producing hCG, then the hCG test can be used to help detect and monitor tumor activity.
When testing hCG as a tumor marker, unlike detecting pregnancy, it is important to measure the intact (alpha + beta subunits) form of hCG. There may be some benefit to also measuring the beta-subunit of hCG in certain tumors, and different labs will detect intact and βhCG differently. For this reason, it is very important to continue to use the same lab when monitoring GTD or germ cell tumors.
When is it ordered?
A quantitative hCG test may be ordered when a healthcare practitioner suspects that a person may have gestational trophoblastic disease (GTD) or a germ cell tumor due to the person's clinical presentation, signs and symptoms.
In women, signs and symptoms of GTD may include:
- Vaginal bleeding during pregnancy
- Fatigue related to anemia (if blood loss is significant)
- Abdominal swelling that may happen more rapidly than with a normal pregnancy
- Pre-eclampsia early in the pregnancy
- Nausea, vomiting that may be more severe than with a normal pregnancy
- A positive pregnancy test (qualitative hCG) but no fetus is seen on ultrasound
- A uterus that remains enlarged after a pregnancy
If a person is diagnosed with one of these conditions and the hCG is initially elevated, then the test will be ordered at intervals to monitor the effectiveness of treatment and to detect tumor recurrence.
What does the test result mean?
In men and in non-pregnant women, the hCG level is normally undetectable.
A high level of hCG occurs in both GTD and normal pregnancy. However, hCG rises at a constant and predictable rate, doubling approximately every 36-48 hours in early normal pregnancy. Levels of hCG in GTD show altered rates of production and, paired with imaging such as ultrasound, can identify abnormalities in the pregnancy requiring intervention. Alternatively, the hCG levels may be much higher than expected in normal pregnancy or not show the expected decrease after pregnancy or abortion/miscarriage.
During treatment for GTD or a germ cell tumor, a falling hCG level generally indicates that the condition is responding to treatment (approximately 50% decrease expected every 1.5 days), while persistent or rising levels may indicate that it is not responding to therapy. An increased hCG level after treatment may indicate a recurrence of disease.
Is there anything else I should know?
False-positive serum hCG results may occur due to the presence of certain drugs such as anticonvulsants, antiparkinsonian agents, hypnotics, and tranquilizers that may interfere with the test. In addition, certain types of antibodies that may be present in some individuals and fragments of the hCG molecule, if present, can also interfere with test results. Generally, if results are questionable, they may be confirmed by testing with a different method.
Rarely, an hCG test may be ordered to help diagnose and monitor tumors and cancers other than GTD or germ cell tumors.
Can urine be tested instead of blood?
If hCG is elevated in the blood, then it will be elevated in the urine, but the results are not interchangeable. Blood is the preferred sample for tumor testing.
Can gestational trophoblastic disease (GTD) be prevented?
No. Other than to avoid becoming pregnant, GTD is not preventable since GTD is associated with pregnancy. However, since it is rare, most women will never have the condition. Since GTD can be detected soon after conception in most cases and successfully treated, it is rarely considered a significant cause to avoid pregnancy.
Can I have a normal pregnancy after having GTD?
Yes, in most cases, although you will be at a higher risk of having GTD again. After treatment for GTD, you will need to wait for a period of time as advised by your healthcare provider before becoming pregnant again.
I heard that some athletes may be tested for hCG. Why is that?
Some athletes, including professional and international athletes, must submit to tests that detect steroids and other performance-enhancing substances. These athletes are often tested throughout their careers to ensure that no 'doping' occurs. Urine tests can detect about 200 compounds, including steroids and other anabolic substances, erythropoietin, and substances that cause false-negative results (masking agents) to hide illicit substance use. Sports organizations specify which compounds they might be looking for by doing a complete screen.
Some athletes who use steroids take beta-hCG to reverse shrinking of their testicles, which can be a side effect of steroids. Thus, some athletes may be tested for hCG to help identify steroid use. (For more on this, see the article on Drug Abuse Testing.)