This test looks for antibodies to thyroglobulin, a protein which is specific to the thyroid gland. Under normal circumstances it does not enter the bloodstream, but if your thyroid is inflamed or under attack from the body's own immune system, then thyroglobulin can be secreted and antibodies detected.
Most cases of thyroid disease are caused by an autoimmune condition where the thyroid gland is attacked by the body's own immune system. This can cause the thyroid gland to produce more thyroid hormone (as in the case of Graves' disease) or to produce less as the cells in the thyroid gland are gradually destroyed (as in the case of Hashimoto's thyroiditis).
What might a low result mean?
It is normal to have low levels of thyroglobulin antibodies in your blood.
What might a high result mean?
Elevated thyroglobulin antibodies mean that your immune system is attacking your thyroid gland. This can affect the gland's ability to produce thyroid hormones. If you already know that you have a thyroid condition, or your test results show that you are under-producing thyroid hormones, then an autoimmune condition is almost certainly the cause.
Having elevated antibodies raises your risk of going on to develop a thyroid disorder so it is recommended that you regularly monitor your thyroid hormones, especially if you become symptomatic. However, some people with elevated antibodies never go on to develop a thyroid problem.