What are Thyroid Peroxidase (TPO) antibodies?

From the Guidelines

Patients with type 1 diabetes should be considered for testing of antithyroid peroxidase (TPO) antibodies soon after diagnosis, as their presence is predictive of thyroid dysfunction, most commonly hypothyroidism. TPO antibodies are immune proteins that target the thyroid peroxidase enzyme, essential for thyroid hormone production, and are primarily used to diagnose autoimmune thyroid conditions, particularly Hashimoto's thyroiditis 1. A recent study indicated that antithyroid peroxidase antibodies were more predictive than antithyroglobulin antibodies in multivariate analysis 1.

Key Points to Consider

• The presence of TPO antibodies is predictive of thyroid dysfunction, with subclinical hypothyroidism potentially associated with increased risk of symptomatic hypoglycemia and reduced linear growth rate 1.
• Thyroid function tests may be misleading if performed at the time of diagnosis due to the effect of previous hyperglycemia, ketosis, or ketoacidosis, and should be repeated after a period of metabolic stability and good glycemic control 1.
• Measurement of thyroid-stimulating hormone concentrations at diagnosis, when clinically stable or soon after glycemic control has been established, is recommended, with rechecking every 1–2 years or sooner if symptoms suggestive of thyroid dysfunction develop 1.

Management and Monitoring

• If TPO antibodies are elevated, further thyroid function tests like TSH, free T4, and free T3 are usually recommended to assess thyroid function 1.
• Treatment for Hashimoto's with hypothyroidism typically involves levothyroxine, starting at 25-50 mcg daily, adjusted based on TSH levels 1.
• Regular monitoring of thyroid function is important, typically every 6-12 months once stable, as TPO antibodies can remain elevated even with treatment, and their levels do not necessarily correlate with disease severity or guide medication adjustments 1.

From the Research

TPO Antibodies Overview

• TPO antibodies, also known as anti-thyroid peroxidase antibodies, are a type of antibody that can be found in the blood of individuals with autoimmune thyroid disease, such as Hashimoto's thyroiditis 2, 3, 4, 5, 6.
• These antibodies are directed against the thyroid peroxidase enzyme, which is involved in the production of thyroid hormones.
• The presence of TPO antibodies can indicate autoimmune thyroid disease, and they are often used as a diagnostic marker for this condition.

Clinical Significance of TPO Antibodies

• TPO antibodies have been shown to be associated with an increased risk of developing overt hypothyroidism, particularly in individuals with subclinical hypothyroidism 3, 4, 5.
• However, the clinical utility of TPO antibodies in predicting the development of overt hypothyroidism is still unclear, and more research is needed to fully understand their role in this process.
• TPO antibodies have also been linked to systemic inflammation and autoimmune activity in subclinical hypothyroidism, and may be useful in identifying individuals at risk of developing cardiovascular and metabolic complications 4.

Measurement and Interpretation of TPO Antibodies

• TPO antibodies can be measured using a variety of laboratory tests, including enzyme-linked immunosorbent assay (ELISA) and chemiluminescent immunoassay (CLIA) 4, 6.
• The interpretation of TPO antibody results should take into account the clinical context, including the presence of symptoms and other laboratory test results.
• It is also important to be aware of potential pitfalls and caveats in the use of TPO antibody tests, including assay interferences and the effects of concurrent medications 6.

Association with Other Thyroid Conditions

• TPO antibodies have been associated with other thyroid conditions, including Hashimoto's thyroiditis and Graves' disease 2, 3, 6.
• They may also be useful in distinguishing between different types of thyroid disease, such as autoimmune and non-autoimmune forms of hypothyroidism 5.
• Further research is needed to fully understand the relationship between TPO antibodies and other thyroid conditions, and to determine their clinical utility in diagnosis and management.