Hashimoto's Thyroiditis: What It Is, How It's Diagnosed, and How It's Managed

Hashimoto's thyroiditis is an autoimmune condition. Your immune system makes antibodies against your thyroid, and the slow inflammation that follows can, over years, stop it making enough thyroid hormone. It is the most common cause of an underactive thyroid in Australia. It is diagnosed with a thyroid test (TSH and free T4) plus a thyroid antibody test, usually TPO antibodies. It is managed by regular checks while your thyroid is keeping up, and with a daily levothyroxine tablet once it becomes underactive.

If you have just been told you have it, it is normal to feel thrown. This guide explains what it means, how it is confirmed, what usually happens next, and what to ask your doctor.

What is Hashimoto's thyroiditis?

Hashimoto's (also called Hashimoto's disease, chronic lymphocytic thyroiditis or autoimmune thyroiditis) happens when your immune system makes antibodies against proteins in your thyroid, usually thyroid peroxidase (TPO) and sometimes thyroglobulin (Tg). The thyroid becomes slowly inflamed, and over time some people's thyroids can no longer make enough hormone. In countries with enough iodine, including Australia, it is the leading cause of an underactive thyroid.

As the Australian Government's healthdirect service puts it, "Hashimoto's disease has no cure, but it can be treated with the thyroid hormone replacement medicine levothyroxine (thyroxine)." The cause is not fully understood, and it can run in families.

You are far from alone. In a community study in Busselton, Western Australia, about 1 in 8 adults with no known thyroid problem had raised thyroid antibodies. Australian GP guidance puts it at 10 to 15 in every 100 people. Many of them never develop an underactive thyroid.

Hashimoto's symptoms

Hashimoto's usually progresses very slowly over many years. Early on it may cause no noticeable symptoms, and some people only find out from a test done for another reason. When the thyroid stops keeping up, the symptoms are those of an underactive thyroid. healthdirect lists:

• tiredness, weakness and muscle aches
• low mood, poor concentration and poor memory
• feeling the cold, and dry skin or dry, thinning hair
• weight gain and constipation
• heavier or irregular periods
• a swelling at the front of the neck (goitre)

None of these is specific to the thyroid, which is why the diagnosis rests on tests rather than symptoms. Occasionally Hashimoto's swings the other way for a while, and the thyroid releases too much hormone. Our guide to the symptoms of an underactive thyroid goes into more detail.

How is Hashimoto's diagnosed?

Your doctor will ask about your symptoms and family history, feel the front of your neck, then arrange tests.

The thyroid tests

• TSH (thyroid-stimulating hormone) is usually the first test. A raised TSH means your brain is pushing your thyroid harder to keep up.
• Free T4 is the main thyroid hormone. It is usually added if your TSH is out of range. A raised TSH with a low free T4 means an underactive thyroid. A raised TSH with a normal free T4 is called subclinical hypothyroidism.
• TPO antibodies show whether autoimmunity is the cause. Most people with Hashimoto's have them, roughly 9 in 10 in one review, and they can be measured on the same sample.
• Thyroglobulin (Tg) antibodies are sometimes checked too. They are less common in Hashimoto's, and on their own they are a weaker sign of thyroid disease.

A small group of people have the typical pattern of Hashimoto's with negative antibody tests, so a negative result does not always settle the question. Your doctor looks at the whole picture.

Antibodies and thyroid function are two different things

This is the part that causes the most confusion. Antibodies tell you the immune process is there. TSH and free T4 tell you how well your thyroid is keeping up right now. You can have positive antibodies with completely normal TSH and free T4. That is still Hashimoto's, but your thyroid is coping, and Australian guidance says no treatment is needed at that stage. Our guide to high thyroid antibodies with a normal TSH explains what that means for you.

Do you need an ultrasound?

Usually not. Australian GP guidance says thyroid imaging, including ultrasound, is not needed to investigate an underactive thyroid. It is used if your doctor feels a lump or an enlarged thyroid. Hashimoto's can look typical on ultrasound, but the tests are what confirm it, and an unnecessary scan can find small, harmless nodules that lead to more tests.

How is Hashimoto's managed?

Management depends on how your thyroid is working, not on the diagnosis alone. "Hashimoto's" covers everything from a thyroid that is coping well to one that needs full replacement.

If your thyroid is still keeping up

If your antibodies are positive but your TSH and free T4 are normal, the usual plan is watching rather than medication, with a TSH check about once a year. An Australian study that followed people for 13 years found that, among those with thyroid antibodies, the starting TSH level mattered most: the lower it was, the less likely an underactive thyroid developed.

If your TSH is only mildly raised

A single mildly raised TSH is often repeated before anything is decided, because in around half of people it settles on its own. Your doctor will usually recheck your TSH and free T4 about 6 to 8 weeks later. If it stays mildly raised, treatment is a judgement call. A major international guideline recommends against routine treatment for most adults at this stage, with exceptions such as a very high TSH, significant symptoms, younger age or plans for pregnancy.

If your thyroid is underactive

If your TSH is raised and your free T4 is low, the standard treatment is levothyroxine, a daily tablet that replaces the hormone your thyroid can no longer make. It is taken once a day on an empty stomach, and many people take it for life. The Australian label says to wait at least 30 minutes, preferably 60, before eating. Once you start or change a dose, your thyroid is usually rechecked about six weeks later, then less often, typically about once a year once you are stable. Our guide to levothyroxine in Australia covers the brands and how to take it.

Most people feel better once their levels are right, but about 1 in 10 still have symptoms despite results in range. If that is you, raise it rather than pushing through. Our guide to still feeling tired with a normal TSH covers what to ask.

Your antibody number will move, and that is fine

Antibody levels often go up and down. Australian Prescriber notes that TPO antibody levels fluctuate, that this "has no clinical significance", and that repeat antibody testing is not recommended. The numbers that guide treatment are TSH and free T4, not the antibodies.

If you are planning a pregnancy

Tell your doctor early. Thyroid hormone needs usually rise in pregnancy, and guidelines recommend checking TSH before conception and reviewing the dose promptly once pregnancy is confirmed, under your doctor's care.

What doesn't have good evidence

No diet or supplement cures Hashimoto's or stops the immune process, and anything that promises to is worth walking away from.

• Going gluten-free. If you have coeliac disease, a strict gluten-free diet matters. Without coeliac disease, the trials are few and small, and a 2025 review rated the evidence very uncertain, with no clear change in TSH or thyroid hormone results. The Australian Thyroid Foundation advises being tested for coeliac disease before cutting gluten, because going gluten-free first can make the test unreliable. Our guide to whether gluten-free helps Hashimoto's goes through the studies.
• Selenium. It has been studied a lot in Hashimoto's. Trials have generally lowered antibody numbers, but reviewers have not found a clear improvement in how the condition behaves or how people feel. More is not better, because too much selenium carries its own risks. Talk to your doctor before adding it.
• Iodine and kelp. Extra iodine from tablets, kelp or seaweed supplements is best avoided unless your doctor recommends it, as people with autoimmune thyroid disease can be more sensitive to too much iodine. You don't need to cut bread or iodised salt.
• Special diets. There is no Hashimoto's diet with strong evidence behind it. Our guide to the Hashimoto's diet evidence looks at the popular ones.

Other conditions that can travel with it

Autoimmune conditions sometimes cluster. In a large UK clinic study, about 1 in 7 people with Hashimoto's reported another autoimmune condition. Coeliac disease is more common than usual (confirmed in about 1 in 62 people with autoimmune thyroid disease in one review), and low vitamin B12 and low vitamin D are both seen more often alongside thyroid conditions. That is not a reason to test for everything, but it is a reason to mention new or unexplained symptoms, such as gut trouble or pins and needles, rather than putting them all down to your thyroid.

Questions to take to your next appointment

• What were my TSH and free T4, and is my thyroid underactive right now or still in range?
• Do I need treatment now, or are we watching and retesting? What would change that?
• When will you recheck my thyroid, and how often after that?
• Do my antibodies need rechecking, and should I worry if the number changes?
• Can I have copies of my results?
• If I start levothyroxine, how should I take it, and could any of my other medicines or supplements interfere?
• Given my symptoms, should I be checked for anything else, such as coeliac disease or low B12?
• If I plan a pregnancy, what should I do and when should I tell you?

Where ThyroBase fits

A diagnosis is a medical matter first, worked through with your doctor. ThyroBase is a daily morning and evening nutrition powder, a food rather than a medicine, with no added iodine and no kelp. It sits alongside your thyroid medication, never instead of it, and both serves contain minerals, so keep them several hours away from your tablet. Here is who ThyroBase is, and is not, designed for.

A diagnosis is a starting point, not a verdict. Most people with Hashimoto's live full, ordinary lives, and getting your questions answered early makes that easier.

Frequently asked questions

What is Hashimoto's thyroiditis?

Hashimoto's thyroiditis is an autoimmune condition in which the immune system makes antibodies against the thyroid. Over time the inflammation can stop the thyroid making enough hormone, but not everyone reaches that point. It is the most common cause of an underactive thyroid in Australia.

How do you test for Hashimoto's?

Your doctor checks your TSH and free T4 to see how your thyroid is working, and thyroid antibodies, usually TPO antibodies, to see whether autoimmunity is the cause. Thyroglobulin antibodies are sometimes added. An ultrasound is not usually needed unless your thyroid feels enlarged or lumpy.

Can you have Hashimoto's with normal thyroid levels?

Yes. Many people have positive thyroid antibodies with a normal TSH and free T4, which means the immune process is there but the thyroid is coping. Australian guidance is no treatment at that stage and a TSH check about once a year.

Do I need medication if I have Hashimoto's?

Not always. If your thyroid is underactive, levothyroxine is the standard treatment. If your antibodies are positive but your TSH and free T4 are normal, guidelines recommend monitoring rather than medication, and your doctor decides based on your results and symptoms.

Can Hashimoto's be cured?

No. Australia's healthdirect says Hashimoto's disease has no cure, but it can be treated with levothyroxine when the thyroid becomes underactive. No diet or supplement cures it or stops the immune process.

The honest takeaway

Hashimoto's is common, manageable and very rarely an emergency. It is diagnosed with a thyroid test and an antibody test, and managed according to how your thyroid is working: regular checks while it copes, levothyroxine once it doesn't. Ask what your TSH and free T4 are, find out whether the plan is treatment or watching, test before cutting gluten, check any supplement with your doctor, and give yourself time. Most people settle into this far more easily than the first week suggests.

ThyroBase is a nutritional supplement and is not intended to diagnose, treat, cure, or prevent any disease. It is designed to sit alongside your thyroid medication, not replace it. This article is general information, not medical advice. Never start, stop or change a supplement or prescription medication without speaking to your doctor or pharmacist first.

References

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