Neuroendocrine cells are cells that have both nerve and hormone (endocrine) aspects and are found in organs throughout the body. These cells and the endocrine system glands that they are found in can give rise to a variety of tumors, both benign and malignant. Examples include carcinoid tumors, insulinomas, small cell lung cancers, and neuroblastomas.
Many of these tumors release large quantities of hormones, such as serotonin, catecholamines, or insulin, continuously or intermittently, causing symptoms characteristic for that tumor. However, some neuroendocrine tumors do not release the expected hormones. In either case, neuroendocrine tumors are frequently associated with increased concentrations of CgA.
A CgA test may also be used to help monitor the effectiveness of treatment and detect recurrence of these tumors.
The level of chromogranin A in the blood is normally low. A person with no signs or symptoms and a normal level of CgA is unlikely to have a neuroendocrine tumor. However, the test is not perfect, and it is possible to have a neuroendocrine tumor even if the concentration of CgA is normal.
An increased CgA level in a person with symptoms may indicate the presence of a tumor, but it is not specific for the type of tumor or its location. In order to diagnose the condition, the tumor itself must be located, biopsied, and examined by a pathologist. The healthcare practitioner will frequently follow an abnormal test result with an order for an imaging scan to help locate any tumor(s) that may be present.
Not all patients with a neuroendocrine tumor have typical signs and symptoms. Some tumors do not produce the hormone associated with that tissue or only produce it intermittently.
The concentration of CgA is proportional to the tumor burden - the mass of the tumor. If concentrations of CgA are elevated prior to treatment and then fall, then treatment is likely to have been effective. If monitored levels begin to rise, then the person may have a recurrence of the tumor.
CgA concentrations may be elevated in conditions such as liver disease, inflammatory bowel disease, renal insufficiency, and with stress. These possible causes for elevated CgA levels should be considered when interpreting test results. Chromogranin A can also be increased in people who take proton pump inhibitors (PPIs), which are drugs that reduce the amount of stomach acid.
There are currently no FDA-approved chromogranin A tests. Those CgA tests that have been developed and validated by laboratories are all slightly different, and their results are not interchangeable. When monitoring a patient over time, CgA tests should be performed by the same laboratory so that values can be compared.
This article was last reviewed on December 17, 2015. | This article was last modified on December 17, 2015.
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