From the Guidelines
Elevated Thyroid Peroxidase (TPO) antibodies are a strong indicator of an autoimmune process targeting the thyroid gland, most commonly associated with Hashimoto's thyroiditis, and predict a higher risk of developing overt hypothyroidism, as evidenced by a study published in 2022 1. The presence of these antibodies suggests that the immune system is attacking the thyroid, but it doesn't always mean that thyroid function is currently impaired. To fully assess thyroid health, additional tests like TSH (thyroid-stimulating hormone) and free T4 should be performed. Some key points to consider include:
- Elevated TPO antibodies can also be found in other autoimmune thyroid disorders, such as Graves' disease.
- The presence of anti-TPO antibodies identifies an autoimmune etiology for thyroid dysfunction and predicts a higher risk of developing overt hypothyroidism, as noted in a study published in 2004 1.
- If TPO antibodies are elevated but thyroid function tests are normal, regular monitoring is typically recommended, as there's an increased risk of developing thyroid dysfunction in the future, with a study from 2022 suggesting assessment for additional autoimmune conditions soon after the diagnosis of type 1 diabetes and if symptoms develop 1.
- It's essential to interpret the significance of elevated TPO antibodies in the context of other laboratory findings and clinical symptoms, and consider the potential for thyroid autoimmunity, as discussed in a statement from 2005 1. The most recent and highest quality study, from 2022, provides the strongest evidence for the clinical significance of elevated TPO antibodies, and therefore, it is recommended to consider the presence of TPO antibodies as a predictor of autoimmune thyroid disease and to monitor thyroid function regularly in individuals with elevated TPO antibodies, even if thyroid function tests are currently normal 1.
From the Research
Elevated Thyroid Peroxidase (TPO) Antibodies
Elevated TPO antibodies are associated with several conditions, including:
- Autoimmune thyroid diseases, such as Hashimoto's thyroiditis and Graves' disease 2, 3, 4, 5
- Thyroiditis, with clearly elevated anti-TPO values found in 59% of patients with thyroiditis 2
- Non-thyroidal illness, although the mean anti-TPO levels in these patients were not significantly elevated 2
Diagnostic Validity of Anti-TPO Assay
The diagnostic validity of the anti-TPO assay has been evaluated in several studies, with results showing:
- A sensitivity of 96% for Hashimoto's thyroiditis and 59% for Graves' disease, with a specificity of 100% 2
- A positive correlation between TPOAb levels and the number of symptoms in HT patients, suggesting a role of thyroid autoimmunity in clinical manifestations of HT 6
- A decline in TPO-Ab levels in most patients with Hashimoto's thyroiditis who are taking levothyroxine, although TPO-Ab levels became negative in only a minority of patients 4
Association with Inflammation and Symptoms
Elevated TPO antibodies have been associated with:
- Inflammation, with positive correlations between TPO-Ab and pro-inflammatory factors such as TNF-α and IFN-γ 5
- Multiple extrathyroidal symptoms, including digestive, endocrine, neuropsychiatric, and mucocutaneous symptoms 5
- A negative association with health-related life quality, with elevated thyroid antibodies inversely correlated with general health and vitality parameters 5