Topic Overview

The immune system may produce antithyroid antibodies that destroy thyroid tissue. An antithyroid antibody test determines whether you have these antibodies.

Increased levels of antithyroid antibodies may mean that you have autoimmune hypothyroidism (Hashimoto's thyroiditis) or autoimmune hyperthyroidism (Graves' disease). But some people who have hypothyroidism or hyperthyroidism never test positive for antithyroid antibodies. Also, people who test positive for antithyroid antibodies may never develop hypothyroidism or hyperthyroidism.

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.