What level of Thyroid Peroxidase (TPO) antibodies is considered high?

From the Guidelines

TPO antibody levels above 35 IU/mL are generally considered high and may indicate autoimmune thyroid disease. When evaluating the level of TPO antibodies, it's essential to consider the clinical context and potential risks associated with elevated levels. According to a study published in JAMA 1, the presence of anti-TPO antibodies predicts a higher risk of developing overt hypothyroidism. Some key points to consider when interpreting TPO antibody levels include:

• Elevated TPO antibody levels can indicate an autoimmune etiology for thyroid dysfunction
• The presence of anti-TPO antibodies does not change the diagnosis of subclinical hypothyroidism, which is based on serum TSH measurements
• Individuals with elevated TPO antibodies have an increased risk of developing hypothyroidism over time, with a risk of 4.3% per year compared to 2.6% per year in antibody-negative individuals, as reported in the study 1. Regular monitoring of thyroid function through TSH and free T4 tests is recommended, even with normal thyroid function, to promptly identify any potential issues.

From the Research

Definition of High TPO Antibody Levels

• High levels of TPO antibodies are generally considered to be above 500 units/ml, as seen in studies 2, 3
• However, some studies suggest that even lower levels, such as above 200 units/ml, can be indicative of autoimmune thyroid disease 2
• Other studies have used different cutoffs, such as 1300 IU/mL, to indicate multifocal papillary thyroid cancer in Hashimoto's thyroiditis patients 4

Association with Thyroid Disease

• Elevated TPO antibody levels have been associated with an increased risk of developing hypothyroidism in autoimmune thyroiditis 3
• High TPO antibody levels have also been linked to Hashimoto's thyroiditis and Graves' disease 2
• In some cases, high TPO antibody levels may be indicative of multifocal papillary thyroid cancer in Hashimoto's thyroiditis patients 4

Clinical Significance

• The presence of high TPO antibody levels can be used to help diagnose and monitor thyroid disease 2, 3, 5
• However, the clinical significance of high TPO antibody levels can vary depending on the individual and the specific disease being diagnosed or monitored 6
• In some cases, high TPO antibody levels may not be associated with significant changes in thyroid function or other clinical outcomes 6