Anti-TPO antibodies: what they are, what they tell you and when they’re tested

Anti-TPO antibodies are antibodies your immune system makes, by mistake, against thyroid peroxidase: an enzyme your thyroid uses to make its hormones. They are the most common sign of Hashimoto’s thyroiditis. Many people have them and feel well.

When they’re tested

Doctors mostly order them when TSH is high, to see whether Hashimoto’s thyroiditis is the cause. They also order them if an ultrasound shows an inflamed thyroid, if there is a goitre, or before and during pregnancy if TSH is not right.

They are not needed for people who feel well and have a normal TSH: having them changes nothing for now, and there is no treatment that makes them go away.

That is why Rosa does not test them. Rosa measures TSH, which shows whether your thyroid is already working less, and explains it together with the rest of the panel.

What they tell you, and what they do not

If they are positive, your immune system is attacking your thyroid. It is usually Hashimoto’s thyroiditis, which works slowly, often over years.

They do not say how your thyroid is working right now, though. TSH and FT4 tell you that. Many people with positive antibodies have a thyroid that works well, for years.

The number matters less than it seems: higher antibodies do not mean your thyroid is worse right now. What counts is whether they are positive or negative, and how TSH is doing.

That is why they are read together with other tests:

Normal anti-TPO antibody levels

Your report usually says whether they are negative or positive, above a limit the lab sets. The limit varies a lot from one method to another: a number that is positive at one lab can be negative at another.

So always look at the limit printed on your report, and do not compare numbers from two different labs.

Anti-TPO antibodies are common: about one adult in ten has them, more often women, and they become more frequent with age.

If your anti-TPO antibodies are positive or negative

High anti-TPO antibodies: what it means

There is usually an autoimmune thyroiditis. The most common situations:

High antibodies and a normal TSH: what to do

If the antibodies are positive but TSH is normal, usually no treatment is needed. Your thyroid is working well, and thyroid hormone is not taken to bring the antibodies down.

Over the years, though, the thyroid can slow down. That is why your doctor usually has TSH rechecked now and then, and sooner if tiredness, feeling cold or weight gain appear.

If you are pregnant or trying for a baby, tell your gynaecologist: with positive antibodies, TSH needs closer follow-up.

No diet reliably makes them go away. Selenium and vitamin D have been studied, with uncertain results: ask your doctor before taking supplements.

What to know before you read the result

A few details help you not to be alarmed by a number.

When to worry

Talk to your doctor if:

Frequently asked questions

What are normal anti-TPO antibody levels? It depends on the lab. Your report gives a limit: below it is negative, above it is positive. The limit varies a lot between methods, so the one on your own report is what counts.

High anti-TPO antibodies with a normal TSH: do I need treatment? Usually not. Your thyroid works well, and thyroid hormone is not taken to lower the antibodies. Your doctor has TSH rechecked over time, because the thyroid can slow down over the years.

Do high anti-TPO antibodies mean Hashimoto’s? In most cases yes, they are the sign of Hashimoto’s thyroiditis. The diagnosis is made by your doctor, though, with TSH, an ultrasound and an examination.

Can diet lower anti-TPO antibodies? No diet reliably makes them go away. Selenium and vitamin D have been studied, with uncertain results. Ask your doctor before taking supplements.

Does Rosa test anti-TPO antibodies? No. Rosa measures TSH, which shows whether your thyroid is already working less. If your doctor wants anti-TPO antibodies, they order them separately.

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