Are thyroperoxidase (TPO) antibodies elevated in Hashimoto’s thyroiditis?

Thyroperoxidase Antibodies in Hashimoto's Thyroiditis

Yes, thyroperoxidase (TPO) antibodies are typically elevated in Hashimoto's thyroiditis and are a key diagnostic marker for this autoimmune thyroid disease. According to current guidelines, the presence of TPO antibodies is a hallmark feature of Hashimoto's thyroiditis and indicates an increased risk for developing hypothyroidism 1.

Diagnostic Value of TPO Antibodies

• TPO antibodies are found in the majority of patients with Hashimoto's thyroiditis, with studies showing positivity in approximately 66% of cases even years before clinical diagnosis 2
• TPO antibodies serve as a marker of autoimmune thyroid disease, particularly Hashimoto's thyroiditis 1
• The NHANES III study specifically excluded individuals with detectable TPO antibodies when establishing reference ranges for thyroid function tests, recognizing their strong association with thyroid disease 3

Clinical Significance of TPO Antibodies

• TPO antibodies are positively associated with:

  • Inflammation markers (TNF-α and IFN-γ) 4
  • Multiple extrathyroidal symptoms despite euthyroid status 4
  • Symptom burden including digestive, neuropsychiatric, and mucocutaneous manifestations 4
  • Decreased health-related quality of life 4

• TPO antibody levels may remain elevated despite treatment:

  • While levothyroxine treatment often leads to a decline in TPO antibody levels (mean decrease of 70% after 5 years), they become negative in only about 16% of patients 5
  • This persistent elevation may explain why some patients continue to experience symptoms despite achieving biochemical euthyroidism 4

Relationship with Other Thyroid Antibodies

• Hashimoto's thyroiditis is often characterized by the presence of both TPO antibodies and thyroglobulin (TG) antibodies 6
• Some patients have bispecific antibodies (TGPO) that cross-react with both TPO and thyroglobulin 6
• In Hashimoto's thyroiditis:
  • TPO antibodies are present in approximately 66% of cases
  • TG antibodies are present in approximately 53% of cases 2
  • These antibodies may be present years before clinical diagnosis 2

Clinical Application

• Patients with positive TPO antibodies should have annual TSH monitoring, even if initially euthyroid, to detect progression to hypothyroidism 1
• The presence of TPO antibodies in combination with elevated TSH confirms the diagnosis of autoimmune hypothyroidism (Hashimoto's thyroiditis) 1
• Screening for other autoimmune disorders should be considered in patients with positive thyroid antibodies 1

Important Caveats

• Not all patients with Hashimoto's thyroiditis have detectable TPO antibodies, so the absence of antibodies does not rule out the disease
• TPO antibodies can occasionally be found in other autoimmune conditions and in some apparently healthy individuals 2
• The relationship between antibody titers and disease severity is not always straightforward, though higher levels are generally associated with increased symptom burden 4, 7

In summary, TPO antibodies are a key diagnostic feature of Hashimoto's thyroiditis and their detection is an important component of the diagnostic workup for suspected autoimmune thyroid disease.