Thyroid antibodies include thyroid peroxidase antibody, thyroglobulin antibody and thyroid-stimulating hormone receptor antibody. Antibody testing is not part of routine thyroid evaluation and is only indicated if a person has an enlarged thyroid or displays symptoms suggesting thyroid dysfunction. According to the American Association for Clinical Chemistry, more routine screenings of the thyroid normally include tests such as TSH and T4.
A thyroid antibody test is primarily used to help diagnose an autoimmune thyroid disease and to rule out other potential thyroid dysfunctions. These tests are generally ordered when a person has high or low thyroid hormone levels, notes the American Association for Clinical Chemistry. It can take several days to receive test results since specialized equipment is needed to conduct the analysis.
In general, if thyroid antibodies are discovered by the testing, it is indicative of an autoimmune thyroid issue. Particular attention is given to rising antibody levels, as opposed to high, but stable levels, since this demonstrates an increase in autoimmune activity, equating to a worsening condition. Examples of autoimmune disorders that are indicated by mild-to-moderately elevated thyroid antibodies include Type 1 diabetes, autoimmune collagen vascular diseases, pernicious anemia and rheumatoid arthritis. The presence of significantly increased antibody levels generally indicates conditions such as Hashimoto thyroiditis and Graves' disease, according to the American Association for Clinical Chemistry.