thyroglobulin

Why this test may be ordered

• Before starting treatment for thyroid cancer to establish a baseline
• Four to six weeks after treatment for thyroid cancer to check whether all thyroid tissue has been removed
• Regularly after successful treatment to make sure cancer has not come back
• To monitor noncancerous thyroid conditions such as hyperthyroidism or hypothyroidism

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.

A health care professional will take a blood sample from a vein in your arm using a small needle. The procedure usually takes less than five minutes.

There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

Understanding results

The meaning of your results depends on your health history, the type of treatment you had, and the results of other tests. Ask your provider to explain what your test results say about your health.

• Very low levels or no thyroglobulin after treatment for thyroid cancer: May mean that your cancer treatment successfully removed all thyroid tissue, including cancerous tissue. However, you will still need more testing over time to make sure. Limitation: Other thyroid conditions and certain illnesses can also affect thyroglobulin levels. Labs use different methods that can affect results, so it is important to have tests done the same way, usually in the same lab. Thyroglobulin antibodies in your blood can make levels appear lower than they really are. Next step: Routine
• Thyroglobulin levels that stay high or increase after treatment for thyroid cancer: May mean that your treatment did not successfully remove all thyroid tissue or that you still have thyroid cancer. It may also mean that your cancer has grown and/or spread. Limitation: Other thyroid conditions and certain illnesses can also affect thyroglobulin levels. Labs use different methods that can affect results, so it is important to have tests done the same way, usually in the same lab. Thyroglobulin antibodies in your blood can make levels appear lower than they really are. Next step: Prompt
• Thyroglobulin levels that were low after treatment but later increased: May mean that your thyroid cancer has come back after treatment. Limitation: Other thyroid conditions and certain illnesses can also affect thyroglobulin levels. Labs use different methods that can affect results, so it is important to have tests done the same way, usually in the same lab. Thyroglobulin antibodies in your blood can make levels appear lower than they really are. Next step: Prompt

• 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.

• What do my thyroglobulin test results mean for my specific health situation?
• Do I need to have my tests done at the same lab each time?
• Should I be tested for thyroglobulin antibodies before relying on this test?

Evidence source

U.S. National Library of Medicine: thyroglobulin