Thyroglobulin is produced by normal or cancerous thyroid cells. When a person develops an autoimmune disease that attacks the thyroid, the body produces thyroglobulin antibodies that damage the thyroid. The test can be used to distinguish an autoimmune thyroid disease from other thyroid diseases, for example, to find the causes of goiter or high or low thyroid hormone levels. Have you had unexplained weight loss or gain, fatigue, hair loss, goiter, anxiety or racing heart rate? These symptoms may be due to hypo- or hyperthyroidism. The Thyroglobulin AB test is normally used to diagnose thyroid autoimmune diseases that are causing thyroid symptoms, such as Graves disease, Hashimoto thyroiditis or thyroid cancer. It may also be used when an existing non-thyroid autoimmune disorder may be causing symptoms due to thyroid problems. Symptoms that may indicate you should have your thyroid function checked include: •Unexplained weight loss or gain •Hair loss •Fatigue •Difficulty sleeping •Anxiety, tremors or rapid heart rate •Protruding eyes •Goiter (enlarged thyroid gland) If your thyroid was removed because of cancer your doctor may want to monitor the levels of thyroglobulin in the body. High levels are a way to monitor whether the cancer has metastasized (spread) to other parts of your body. If you have high thyroglobulin antibodies it will be difficult for the doctor to determine the level of thyroglobulin and this test can be used to determine if a high level of antibodies is interfering with the monitoring of these levels.