The
immune system may produce antithyroid
antibodies that destroy thyroid tissue. An antithyroid
antibody test determines whether you have these antibodies.
If you test positive for antithyroid antibodies, you may have
Hashimoto's thyroiditis, the most common cause of
hypothyroidism. However, many people with
hypothyroidism never test positive for antithyroid antibodies. Also, people who
test positive for antithyroid antibodies may never develop hypothyroidism. Some
people who test positive for antithyroid antibodies develop
hyperthyroidism (Graves' disease).
If you have mild (subclinical) hypothyroidism, the presence of
antithyroid antibodies can help predict how likely it is that you will develop
hypothyroidism that eventually causes symptoms.