The TPO in anti-TPO stands for Thyroid Peroxidase. An anti-TPO test is done to detect antibodies against TPO in the blood. There is a small gland in our body located in front of the neck. This gland is the thyroid gland. It is a vital part of our body and controls various factors of our body such as influencing metabolism, growth and development and body temperature. During infancy and childhood, adequate thyroid hormone is crucial for brain development.