thyroglobulin
Reviewed
A thyroglobulin test measures the amount of a protein called thyroglobulin (Tg) in a blood sample. It is used as a tumor marker to monitor thyroid cancer treatment and detect recurrence, but it is not used alone to diagnose cancer. The test can also help evaluate noncancerous thyroid conditions.
Preparation and collection
You usually do not need any special preparations, but tell your provider about all vitamins and supplements you take because some may need to be avoided.
Understanding this test
Use the reference interval and units printed by the laboratory that performed the test. A result outside that interval is not a diagnosis by itself, and a result inside it does not rule out every condition. Your symptoms, history, medicines, timing, and related tests can change what the result means.
- A thyroglobulin test alone cannot be used to diagnose cancer.
- Other thyroid conditions (hyperthyroidism, hypothyroidism, thyroiditis) and certain illnesses can affect thyroglobulin levels.
- Labs use different methods to measure thyroglobulin, which can affect results. It is important to have tests done the same way, usually in the same lab.
- Thyroglobulin antibodies in your blood can make thyroglobulin levels appear lower than they really are. Your provider will usually order a thyroid antibody test to find out whether thyroglobulin testing will be useful.
What to do next
Your provider will likely check your levels over time instead of relying on a single test result. If you have thyroglobulin antibodies, other tests will be used to see if your cancer treatment was successful.