What is being tested?
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.
- Germ cell tumors can affect cells within the testicles that make sperm and account for more than 90% of testicular cancers.
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.
