Hashimoto: symptoms, causes and the blood values behind it

Hashimoto is an autoimmune condition in which your immune system attacks your own thyroid. Over time that thyroid often starts working more slowly. It is the most common cause of an underactive thyroid, and women get it roughly seven to ten times more often than men. Three blood values carry most of the story: TSH, free T4 and anti-TPO.

Here is what strikes me about most Dutch writing on Hashimoto. A lot gets claimed and very little gets measured. You read about gluten, guts and inflammation. You rarely read which number actually changes, or in what order.

That is a shame. This is one of the few conditions where you can genuinely follow the course.

What is Hashimoto's disease?

Hashimoto's disease is a chronic inflammation of the thyroid caused by your own immune system. Antibodies target thyroid tissue, especially an enzyme called TPO. The tissue is slowly damaged, which means thyroid hormone production can gradually fall.

Your thyroid sits at the front of your neck, just below the Adam's apple. It makes two hormones, T4 and T3. Together they help set how fast nearly every cell in your body works, from your heart rate to your gut to your hair growth.

With Hashimoto that process is usually slow. A review in Autoimmunity Reviews describes a condition that develops over years, with antibodies often present well before symptoms appear (Ralli et al., 2020). Some women have raised antibodies for years and nothing else.

According to Thuisarts.nl, thyroid function stays normal in a proportion of people with Hashimoto. Having the condition does not automatically mean your thyroid gives up.

What are the symptoms of Hashimoto's disease?

Hashimoto symptoms come mainly from the thyroid slowing down. Fatigue, feeling cold, weight gain, dry skin, hair loss, constipation and slower thinking are the most common. They tend to creep in over months, which is why many women first blame a busy life or their age.

That creeping quality is exactly the problem. There is no day when you think, today I got ill. There is only a winter when you are colder than usual, and a year when your hair gets thinner.

Symptoms that come up often:

• Fatigue that a good night of sleep does not fix
• Feeling cold easily, especially hands and feet
• A few kilos of weight gain without eating differently
• Dry skin, more brittle hair or nails
• Slower to get going, trouble concentrating
• Heavier or irregular periods
• Low mood, or a flatter feeling generally
• A full or pressing sensation at the front of the neck

In some women Hashimoto starts with a short phase where the thyroid temporarily runs fast. Palpitations, restlessness and weight loss belong to that phase. It can be confusing, because it is the opposite picture. Our article on an overactive thyroid covers it.

Why do women get Hashimoto so much more often?

Hashimoto is roughly seven to ten times more common in women than in men. The exact reason is not settled. Researchers point to the role of sex hormones in the immune response, to the X chromosome, and to moments when the immune system shifts sharply, such as after a pregnancy.

Autoimmune conditions in general affect women more often. You see the same pattern in rheumatoid arthritis, coeliac disease and lupus. Having one autoimmune condition raises the chance of a second.

That combination matters clinically. Coeliac disease and Hashimoto occur together more often than chance would predict. If you recognise several patterns in yourself, our overview of autoimmune disease symptoms in women can help you organise the story, and coeliac disease symptoms in women goes deeper on that second condition.

There is one more reason this hits women harder. The age at which Hashimoto often becomes visible overlaps with perimenopause. More on that below.

Which blood values go with Hashimoto?

Three values carry most of the information. TSH is the signal from your pituitary and rises when your thyroid falls behind. Free T4 is the hormone your thyroid makes itself and falls with an underactive thyroid. Anti-TPO are the antibodies that make the autoimmune cause visible.

The order is the interesting part. Anti-TPO is often raised years before TSH moves. TSH rises next, while free T4 is still normal. Only later does free T4 come down with it.

Reference ranges differ per laboratory, so always read your result against the range printed on your own report. What each number means is worked out in thyroid values explained. Per marker you can also read our pages on TSH, free T4 and anti-TPO.

Ferritin belongs in this list because it moves along so often. Heavier periods with a slow thyroid cost iron, and low ferritin produces symptoms that look like Hashimoto. Our article on iron deficiency without anaemia explains why the two get tangled.

How do you know if you have Hashimoto?

Hashimoto is identified from your symptoms, a blood test for TSH, free T4 and anti-TPO, and sometimes an ultrasound of the neck. Raised anti-TPO points to the autoimmune cause. What your thyroid is doing right now shows up in TSH and free T4. Your GP puts those pieces together.

Two examples make it concrete. Imagine two women of 43 with the same complaint: tired for months, cold, and losing hair.

In the first, TSH is 2.1 mIU/L, free T4 sits mid-range, and anti-TPO is strongly raised. Her thyroid is working fine today. The antibodies say something about the chance that this changes, but they do not explain her tiredness now. Her low ferritin might.

In the second, TSH is 8.4 mIU/L and free T4 is just below range, with the same raised anti-TPO. That is a different picture, and that conversation with the GP goes somewhere else.

Same symptoms, same antibodies, different situation. Which is exactly why a single number without the rest says very little.

The Dutch NHG guidance on thyroid conditions describes TSH as the value GPs generally start with, adding free T4 when TSH is abnormal. If you want to know how self-testing compares with the route via your GP, thyroid testing: home test or blood test covers it.

Hashimoto or menopause: how do you tell them apart?

This is the hardest question in this article, and the reason Hashimoto is often spotted late in women. Fatigue, weight gain, low mood, hair loss, poor sleep and a changing cycle fit both. The difference sits in the symptoms that do not overlap.

The rule of thumb I find most useful here: hot flushes point towards menopause, feeling cold points towards your thyroid. If you are hot and cold at the same time, you may well have both at once, and that happens more often than people expect.

We work that distinction out further in slow thyroid and menopause. For the broader symptom list, thyroid symptoms in women is the starting point.

How serious is Hashimoto's disease?

Hashimoto is a chronic condition, but for most people a very followable one. It does not resolve on its own. The course is often slow, though, and a proportion of people with raised antibodies keep normal thyroid function for years. That makes the picture less alarming than the name suggests.

The best known figures on the course come from the Whickham Survey, a British population study with twenty years of follow-up (Vanderpump et al., 1995). The yearly chance of developing an underactive thyroid was highest in women who had both a raised TSH and antibodies. With only a raised TSH, or only antibodies, that chance was clearly lower.

What that means in practice: antibodies alone are not a diagnosis of an underactive thyroid. They say something about direction, not about today.

I think that nuance is missing from most articles on this. A raised anti-TPO gets presented as though the verdict is in, when it is mainly a reason to keep looking at your symptoms and your values together with your GP.

What does Hashimoto do to your body long term?

When the thyroid slows, a large part of your metabolism slows with it. That can touch your heart rate, your cholesterol, your gut, your cycle and your mood. With well-adjusted thyroid values many of those effects settle again, though it takes months rather than weeks.

For women who want to conceive there is an extra point. Thyroid hormone plays a role in the cycle and in early pregnancy. Work by Krassas and colleagues found menstrual disturbances more often in women with an underactive thyroid than in women without (Krassas et al., 1999). What that means concretely is in our spoke on the thyroid and your cycle, and thyroid and pregnancy covers the period after.

Other common questions get their own article in this cluster:

• Levothyroxine side effects, on Euthyrox, Thyrax and why the timing of your dose moves your TSH
• The Hashimoto diet, where we grade each claim against what the research actually shows
• Losing weight with an underactive thyroid, with honest expectations about how much comes back
• Thyroid and hair loss, including why medication can increase shedding at first

What to discuss with your GP

If you take these symptoms to your GP, it helps to make the story concrete. Note when the symptoms started, how your cycle has changed, and whether thyroid or other autoimmune conditions run in your family. Bring earlier results if you have them, because the trend says more than one measurement.

Women's symptoms still get written off as vague more often than men's. We wrote about that in not taken seriously. A timeline with dates and numbers makes that conversation measurable instead of impressionistic.

If you want a baseline before you have that conversation, our Thyroid Complete looks at TSH, free T4, free T3 and anti-TPO in one draw. For the basic values there is the smaller Thyroid Function, and where tiredness has several possible causes the Tiredness panel looks wider.

What I would leave you with: do not let one number rattle you. Ask about the pattern, not the snapshot.

Every blood test result includes a professional assessment from a BIG-registered doctor. For treatment decisions, discuss your results with your GP.

References

• Ralli M, et al. Hashimoto's thyroiditis: An update on pathogenic mechanisms, diagnostic protocols, therapeutic strategies, and potential malignant transformation. Autoimmunity Reviews, 2020. PMID 32805423
• Vanderpump MP, et al. The incidence of thyroid disorders in the community: a twenty-year follow-up of the Whickham Survey. Clinical Endocrinology (Oxford), 1995. PMID 7641412
• Krassas GE, et al. Disturbances of menstruation in hypothyroidism. Clinical Endocrinology (Oxford), 1999. PMID 10468932
• NHG guidance on thyroid conditions, Dutch College of General Practitioners
• Thuisarts.nl, patient information on the thyroid and thyroid inflammation