An **Anti-Microsomal Antibodies** test is a diagnostic blood assay primarily used to detect and manage autoimmune thyroid disorders. These antibodies target thyroid microsomal antigens, which are now recognized as the enzyme **thyroid peroxidase (TPO)**. Consequently, this test is widely known as the **Anti-TPO antibody test**.
Elevated levels of anti-microsomal antibodies are a classic hallmark of **Hashimoto’s thyroiditis** (autoimmune hypothyroidism) and are also frequently elevated in **Graves' disease** (autoimmune hyperthyroidism). Measuring these antibodies helps clinicians confirm an autoimmune origin for thyroid dysfunction, predict the progression of subclinical hypothyroidism, and evaluate postpartum thyroiditis risks.