Thyroglobulin
A thyroglobulin test measures the amount of a protein called thyroglobulin (Tg) in a sample of your blood.
A thyroglobulin test measures the amount of a protein called thyroglobulin (Tg) in a sample of your blood. Your thyroid (a small, butterfly-shaped gland in your neck) makes thyroglobulin along with many other important hormones . Together, these hormones control bodily activities such as your heart rate and how fast you burn calories from food. Normally, your thyroid releases small amounts of thyroglobulin into your bloodstream. However, various conditions that affect the thyroid can lead to higher levels of this protein. The most common causes of high thyroglobulin levels are two types of thyroid cancer called papillary carcinoma and follicular thyroid cancer. In both conditions, cancerous cells produce thyroglobulin. Because of this, thyroglobulin is usually measured as a tumor marker . Tumor markers are substances made by cancer cells and/or by normal cells in response to cancer in your body. Other conditions can, however, affect your thyroglobulin levels. These include various thyroid diseases such as: Hyperthyroidism , a condition where your thyroid becomes overactive and makes too much thyroglobulin. Hypothyroidism , a condition where your thyroid becomes underactive and makes too little thyroglobulin. Thyroiditis, a condition caused by inflammation of the thyroid, which can lead to a temporary rise in thyroglobulin levels. Because such a wide range of conditions can affect thyroglobulin levels, health care providers don’t use the results from a thyroglobulin test to diagnose cancer. Other names: Tg, TGB, thyroglobulin tumor marker
Why is this test ordered? You may need a thyroglobulin test before starting treatment for thyroid cancer. Your provider will compare these test results to your test results after treatment. You may also need this test: 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 hasn’t come back. If your provider is monitoring a thyroid condition that isn’t cancer, a thyroglobulin test can help evaluate how active your thyroid cells are and how your treatment is working.
Clinical Interpretation
Understanding the results of a thyroglobulin test after treatment can be complicated. The meaning of your results depends on your health history, the type of treatment you had, and the results of other tests. So, it’s best to ask your provider to explain what your test results say about your health. In general, if you were tested after treatment for thyroid cancer: Very low levels or no thyroglobulin 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. Thyroglobulin levels that stay high or increase 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. Thyroglobulin levels that were low after treatment but later increased may mean that your thyroid cancer has come back after treatment. Because other thyroid conditions and certain illnesses can also affect thyroglobulin, your provider will likely check your levels over time instead of relying on a single test result. Learn more about laboratory tests, reference ranges, and understanding results .
Clinical Protocol & Patient Advice
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You usually don’t need any special preparations for a thyroglobulin test. But you need to avoid taking certain vitamins or supplements so tell your provider about everything you take.
Usage Guidance
- Reference ranges vary by laboratory. Always discuss your specific results with a qualified healthcare professional.
Source: MedlinePlus, National Library of Medicine. View the original.