Description

Thyroid peroxidase (TPO) antibodies are proteins produced by the immune system in response to damaged thyroid cells. TPO is an enzyme in the thyroid gland that helps produce hormones that regulate growth and metabolism. When thyroid cells are damaged, TPO leaks into the bloodstream, triggering the immune system to produce antibodies. A thyroid peroxidase antibody test measures the amount of these antibodies in the blood. 

A TPO antibody test may be performed if you have a high TSH level, or if you are pregnant and have an autoimmune condition that affects the thyroid. A positive test result indicates that the cause of hypothyroidism is an autoimmune disease, such as Hashimoto's disease. A negative result could mean that the high TSH is due to another factor, such as a viral infection or medication.

Fasting not required.