Some common thyroid diseases occur when the immune system breaks down and produces antibodies against its own thyroid gland. Antimicrosomal antibodies or anti-TPO (antithyroperoxidase) are the most frequently implicated autoantibodies.
Normal levels of antimicrosomal antibodies have little clinical significance. Moderately high levels are found in thyroid diseases with hypothyroidism, such as Hashimoto thyroiditis or primary myxedema as well as hyperthyroidism (Graves’ disease). In the presence of abnormal thyroid function tests (TSH, T4, T3), positive autoantibodies indicate the probable nature of the thyroid gland damage.
In individuals with normal thyroid function tests, the presence of antimicrosomal antibodies indicates a potential risk of developing thyroid disease. In general, the higher the antibody concentration, the greater the risk of developing autoimmune damage to the thyroid.
The presence of antimicrosomal antibodies in pregnant women increases the risk of hypo or hyperthyroidism in fetuses and newborns.
Antimicrosomal antibodies can also be found in other autoimmune diseases such as type 1 diabetes (juvenile diabetes), pernicious anemia, rheumatoid arthritis and systemic lupus erythematosus (SLE).