Anti-TPO Antibody

Please review Order Guide: TSH, T3, T4, rT3 for information on basic thryoid testing. The following section contains information on auto-immune hypothroidism and anti-TPO antibody testing.

What are the types of hypothyroidism?

• Auto-immune hypothyroidism (AKA Hashimoto’s Disease)

• Hypothyroidism due to iodine deficiency

• Drug-induced hypothyroidism (i.e. amiodarone or lithium)

• Hypothyroidism after radiation treatment

• Central hypothrydoisim (rare - i.e. pituitary apoplexy, surgery, radiation, drug-induced)

What is the most common cause of hypothyroidism in Canada?

Auto-immune hypothyroidism (AKA Hashimoto’s Disease) is the most common form of hypothyroidism in Canada. Iodine is a necessary nutrient to make thyroid hormone. In Canada, people generally have an adequate dietary intake of iodine through fortified foods (i.e. iodine-fortified table salt). Outside of developed countries like Canada, iodine deficiency is the most common cause of hypothyroidism.

What is Hashimoto’s Disease?

Hashimoto’s Disease or Auto-immune hypothyroidism (the most common cause of hypothyroidism in Canada) occurs because your body’s immune system begins attacking its own thyroid gland. The immune system starts making antibodies to a component of your thyroid gland called Thyroid-Peroxidase and Thyroglobulin, causing it to become non-functional. These are called Anti-TPO Antibodies and Anti-Thyroglobulin Antibodies. Approximately 10% of people with Hashimoto’s Thyroiditis can be antibody negative however.

What are anti-TPO Antibodies?

Anti-TPO antibodies when measured high, in the presence of an elevated TSH and low T4 suggest Auto-immune Hypothyroidism. Most guidelines do not recomment routine testing with anti-TPO antibodies as they are not necessary to make a diagnosis of hypothyroidism.

When is ordering an anti-TPO antibody useful?

If you have a TSH between 4 and 10, with a normal Free T4, having anti-TPO antibodies can guide a physician to start treatment. A negative anti-TPO antibody might mean a doctor will monitor your TSH without starting medications if your TSH is between 4-10.

I have a positive anti-TPO Antibody. Do I need to re-measure anti-TPO antibodies?

Auto-immune thyroiditis (Hashimoto’s disease) is a chronic condition and repeat measurement is not necessary.