Thyroid peroxidase (TPO) IgG antibodies
| Category | Immunology |
|---|---|
| Test background |
TPO is a membrane-bound glycoprotein enzyme with a role in the synthesis of T3 and T4. TPO antibodies and thyroglobulin (Tg) antibodies are found in Hashimoto’s thyroiditis (usually at high titre), primary myxoedema, Grave’s disease and postpartum thyroiditis. TPO antibodies can also be found in isolation in a high proportion of patients with autoimmune hypothyroidism. They can also be seen in other autoimmune diseases (rheumatoid arthritis, Addison’s disease, type 1 diabetes), and in up to 20% of healthy people, more frequently in females. NICE UK (NG145, 2019) suggest testing for TPO antibodies in adults and children with TSH levels above the reference range and possibly repeating this test in children as they transition to adult services. NICE UK do not recommend repeat TPO antibody testing in adults. This assay is performed by chemiluminescent microparticle immunoassay. |
| Clinical Indications |
Investigation of primary hypothyroidism |
| Reference range | ≤5.0 IU/ml |
| Sample & container required | Serum (RST rust top) |
| Sample volume | 5-10 mL blood (1 mL serum) |
| Turnaround time | 7 days |