You’re looking at a thyroid panel with a positive TPO, maybe a positive thyroglobulin antibody, maybe even a positive TSI, and the word Hashimoto’s is already rumbling around in your head. With a positive thyroid antibody, one practitioner might definitely call it Hashimoto’s, and another looks at the same panel and wonder if it might indicate Grave’s disease.

A positive antibody is merely a signal, not an absolute diagnosis. It can tell you that the immune system is alert to the thyroid, but it can’t tell you why, when it started, how much damage is happening, or how the thyroid is functioning today.

So the better questions are these: “Is the immune system truly reacting to thyroid tissue-or to something else? Is the thyroid actually dysfunctional? Is there there more to the story that should be investigated??

If you’ve ever second-guessed a thyroid panel, watch the full episode below.

 

Does a Positive TPO Antibody Mean My Patient Has Hashimoto’s?

 

No, a positive TPO antibody on its own doesn’t prove Hashimoto’s, but it doesn’t prove hypothyroidism either. TPO stands for thyroid peroxidase, an enzyme in the thyroid that helps make thyroid hormone. A positive result tells you the immune system is recognizing that enzyme, and it can flag a possible risk of thyroid dysfunction down the road. But it doesn’t tell you what’s actually happening inside the thyroid today.

TPO antibodies are strongly correlated with Hashimoto’s, but they can also be positive in Graves’ disease and in postpartum thyroiditis. They can even show up positive alongside other autoimmune conditions and have nothing to do with the thyroid at all.

A positive thyroid antibody tells you the immune system is recognizing the thyroid, not the state the thyroid is in right now.

Think of the antibody as a stoplight. It could signal red, green, or yellow, depending on what’s happening with the immune system. Let’s say TPO used to be 800 and now it’s 150. Does that mean the thyroid is working better? Or could it mean that the immune system has turned the signal from red to yellow or green? You won’t know for sure until you investigate a little further.

Start with a good history. Look at lab results over time. The antibodies you’re currently seeing might be greatly improved from what they were 3 years ago. Maybe the original issue resolved, and those antibodies are just hanging around, still positive.

But when TPO is sky high, something is going on. The most challenging thyroid patient I’ve ever worked with had a TPO over 8,000 and my first reaction was pure panic. That’s a very different situation from a mildly positive result in a patient whose thyroid looks fine.

 

What Is the Difference Between TPO and Thyroglobulin Antibodies?

 

TPO antibodies are directed at an enzyme, and thyroglobulin antibodies are directed at a specific protein which makes up the scaffolding that thyroid hormones are built on. Both of those components live in the thyroid cell, so a positive result for either tells you the immune system is recognizing thyroid tissue.

The thyroglobulin antibody (TGAb) is more commonly associated with Hashimoto’s, but it can also show up in Graves’ disease as well. It isn’t a measure of hormone production, tissue damage, or how severe the patient’s symptoms are. It simply tells you there is immune activity inside the thyroid cell.

Sometimes TPO comes back completely normal, even when thyroglobulin antibodies are detected. It’s easy to glance at the normal TPO, decide the thyroid is fine, and gloss right over the thyroglobulin result. But this would be a mistake.

TPO and thyroglobulin antibodies tell you the immune system is recognizing thyroid components, but they don’t tell you why it started, how active the damage is, or the health of the thyroid right now.

 

What Do TSI and TSH Receptor Antibodies Actually Measure?

 

TSI and TSH receptor antibodies (TRAb) act at the TSH receptor on the thyroid cell. Normally, the pituitary sends TSH to that receptor as a signal that says, “Release more T4 and T3.” The thyroid responds in turn, relese out more thyroid hormone into the bloodstream to be bound up and carried to the appropriate destinations.

TSI stands for thyroid-stimulating immunoglobulin. It mimics TSH by stimulating the receptor directly, and tells the thyroid to make more hormone without the pituitary ever asking for it. In essence, it’s sending a message to keep making thyroid hormone, even if the body doesn’t need it.

A positive TSI is strongly associated with Graves’ disease, which should prompt a referral for medical evaluation and testing.

TSH receptor antibodies are an umbrella term for a family of antibodies that share the TSH receptor.  But they are not TSH. They do one of three things to the receptor: stimulate it, block it, or exert little to no effect. A blocking TSH antibody can cause a hypothyroid presentation even though the thyroid tissue isn’t the source of the problem. Conversely, stimulating TSH antibody can ‘turn on’ the TSH receptor causing excessive release of thyroid hormone, possibly appearing as hyperthyroid.

Without knowing which of those three is happening, a TRAb result doesn’t provide much information on its own. It needs context. Evaluate it alongside TSH, T4, T3, T3 uptake, and the rest of the standard thyroid markers. Consider the presentation and symptom pattern of the patient as well.

One more thing – if TSI or TSH receptor antibodies are positive and the patient is pregnant, trying to get pregnant, or recently pregnant, be sure to let her OBGYN know. These antibodies can cross the placenta and affect fetal development.

 

Can Infections or Food Proteins Trigger Positive Thyroid Antibodies?

 

They can, and both are biologically plausible, but not in every case. This occurs through a process known as molecular mimicry. Molecular mimicry happens when some kind of protein resembles part of a human protein closely enough that the immune system targets both.

Those triggers can come from an unresolved infection, like food poisoning, or a strange viral illness. They can also come from endogenous microbial proteins that resemble thyroid tissue, or from broader changes in immune regulation and the microbiome.

Food proteins are often key players in this scenario. Dr. Vojdani introduced the idea that dietary proteins can resemble human tissue proteins, causing an immune reaction. One person’s immune system might look at a gluten protein and say, “Yep, that looks like the thyroid” while another person will have no reactivity at all. This can be referred to as cross-reactivity against thyroid tissue.

This is an area of ongoing research in the world of autoimmunity and while mainstream medicine isn’t on board quite yet, it is an established concept that has yet to be included as part of standard autoimmune care.

 

What Should I Check Before I Act on a Positive Thyroid Antibody?

 

Before you do anything, determine the point of action of the antibody – is it against the TSH receptors, thyroglobulin, or thyroid peroxidase? Then look at the full thyroid serum panel to determine what’s happening inside the gland. And then decide what to do next. Remember, TPO and thyroglobulin antibodies are directed at components of the thyroid cell itself while TSI and TSH receptor antibodies act at the TSH receptor.

Look at free T4, free T3, total T4, total T3, and T3 uptake. Remember that most of what the thyroid releases is T4 (roughly 80-90%), a prohormone that has to convert into T3. Low T3 doesn’t automatically mean the thyroid isn’t making enough T4 – it could simply mean the body isn’t converting T4 into T3 effectively.

Ask if the patient is on levothyroxine, Armour, or T3. Ask about biotin, which can interfere with thyroid lab results and often shows up in hair, skin, and nail supplements. Ask about pregnancy, thyroid surgery, nodules, radioactive iodine, other medications, and determine the current stage of her reproductive life.

 

Call to Action

 

Subscribe to my YouTube channel to learn how to interpret the four essential thyroid antibodies and where each one acts.

And if you’re ready to go deeper, join me live, this Saturday, October 17th for my brand-new online seminar titled Decoding the Thyroid. I’ll walk through 11 of the most common thyroid presentations, show you what markers to order, supplements to consider, which ones to avoid, how to work out any thyroid protocol using the 5-Step Thyroid Framework. If you can’t attend, register anyway. You’ll get the seminar replays, resources, notes, and the 5-Step Thyroid Framework regardless. Click here to register.

 

About

 

Ronda Nelson, PhD, MH, is the founder of Clinical Academy, and host of The Clinical Entrepreneur Show. Drawing from more than 20 years of experience as a practitioner, educator, and business owner, and having trained more than 4,000 wellness practitioners, she provides ongoing clinical training through her membership, Clinical Academy, and her YouTube channel, both designed to help wellness practitioners turn complex clinical topics into actionable knowledge for use with their patients.

 

Related Content

• Decoding the Thyroid – brand-new online seminar happening this Saturday, October 17th, from 8am – 3pm PT where we’ll talk about all things thyroid including 11 of the most common thyroid presentations and how to support each one.
• The 5 Clinical Non-Negotiables – my free guide to the five areas you need to address with every patient, regardless of whether or not the thyroid is involved.
• Clinical Academy – my clinical membership that helps practitioners turn what they know into sound clinical protocols to use with their patients.

 

Frequently Asked Questions About Positive Thyroid Antibodies

 

Can you have positive TPO antibodies with normal thyroid function?

 

Yes, TPO antibodies can be positive while TSH, T4, and T3 are normal and the patient feels fine. A positive TPO indicates the immune system is recognizing thyroid peroxidase and might indicate a future risk, but it doesn’t necessarily indicate that hypothyroidism is present. It’s still a good idea to investigate why TPO might be elevated which includes evaluating the microbiome, a possible infection, or a food trigger.

 

What is the difference between TSI and TSH receptor antibodies (TRAb)?

 

TSI stimulates the TSH receptor, while TSH receptor antibodies include a broader family of antibodies that can stimulate the receptor, block it, or do almost nothing. TSI and TRAb act directly at the TSH receptor. A stimulating TRAb antibody can cause labs to indicate hyperthyroid while a blocking TRAb antibody can cause hypothyroid lab results, even when the thyroid tissue isn’t the source.

 

Do thyroid antibodies go away after treating an infection?

 

Not necessarily. Thyroid antibodies often stay positive for a long time. Addressing an infection that’s activating the immune system can influence the larger immune response and subsequent inflammation, but it doesn’t mean the antibodies will disappear. A lower number that stays positive may simply be that patient’s new baseline, which is why historical labs matter.

 

Why do TSI and TSH receptor antibodies matter during pregnancy?

 

TSI and TSH receptor antibodies matter during pregnancy because they can cross the placenta and affect fetal development. If a patient is pregnant, trying to conceive, or recently pregnant and either antibody is positive, be sure to let her medical doctor know. This isn’t something to handle on your own.

 

Can biotin affect thyroid lab results?

 

Yes, biotin can interfere with thyroid hormone lab results. Before testing, ask every thyroid patient if biotin is part of their supplement routine, including any hair, skin, and nail supplements.  Ruling it out is a simple step that keeps you from reading the labs incorrectly.

 

Call to Action

 

A single antibody result rarely tells the whole story, because the thyroid never works alone. In the upcoming “Decoding the Thyroid” online seminar, on October 17th, 2026, I’ll give you a 5-Part Thyroid Framework along with checklists and other resources you need to unravel even the most complex thyroid patient. If you can’t make it live, you can still register. You’ll receive the seminar notes, full replay recordings along with all the seminar resources.

Register for Decoding the Thyroid

 

Disclaimer/Disclosure

 

This content is for educational purposes only and is intended for wellness practitioners working within the functional medicine and integrative health space. This episode reflects Ronda Nelson’s personal experience and professional perspective as a practitioner, business owner, and mentor. It is not medical, mental health, legal, or financial advice. Practitioners are responsible for applying this information within their legal and professional scope. Ronda Nelson is the founder and owner of Clinical Business Academy and Clinical Academy, and the creator of the Decoding the Thyroid seminar, all of which are mentioned on this page. No sponsorship or outside compensation was received for these mentions.