What Causes Hashimoto's? What We Know About the Causes

Maybe you spent years living your life without thinking much about your thyroid.

You worked, exercised, made plans, and carried on with everyday life.

And then, suddenly, you hear:

"You have Hashimoto's."

One of your first questions might be:

**"What caused my Hashimoto's?"**

Perhaps you think back to a stressful period. A pregnancy. An infection. Something you ate.

Or you wonder whether you've spent years pushing yourself too hard.

The answer is that, in most cases, we can't identify one clear cause of Hashimoto's.

We know that genetics and the immune system play important roles. Several biological and environmental factors are also associated with an increased risk of thyroid autoimmunity.

But for one individual, we usually can't say:

"This is exactly what caused your Hashimoto's."

What Exactly Is Hashimoto's Disease?

Hashimoto's disease, also called Hashimoto's thyroiditis, is an autoimmune condition affecting the thyroid gland.

Normally, your immune system helps protect you against infections.

In autoimmune conditions, the immune system also reacts against parts of your own body.

In Hashimoto's, the thyroid gland is the target.

Blood tests may detect antibodies against thyroid components, including:

- Anti-TPO: antibodies against thyroid peroxidase.
- Anti-Tg: antibodies against thyroglobulin.

Over time, the autoimmune response can damage thyroid tissue.

Eventually, the thyroid may become unable to produce enough thyroid hormone.

This is called hypothyroidism, or an underactive thyroid.

However, Hashimoto's and hypothyroidism aren't exactly the same thing.

You can have Hashimoto's while your thyroid still produces sufficient hormone.

What Causes Hashimoto's Thyroiditis?

The exact cause of Hashimoto's isn't fully understood.

Researchers believe it develops through a combination of genetic susceptibility, immune system processes, and environmental factors.

That doesn't mean every possible risk factor directly causes the disease.

Two people may have similar genetic backgrounds or experiences, yet only one develops Hashimoto's.

That's why it's important to distinguish between:

- Factors known to increase the risk of Hashimoto's.
- Factors that may play a role but are still being investigated.
- Events that happened around the time of diagnosis without necessarily causing the condition.

That last distinction matters.

Discovering Hashimoto's after a stressful period or an infection doesn't automatically mean that event caused the disease.

Is Hashimoto's Hereditary?

Genetics play an important role in Hashimoto's.

Hashimoto's and other autoimmune thyroid conditions are more common in some families.

If a parent, sibling, or another family member has Hashimoto's or another autoimmune condition, your own risk may be higher.

But having a genetic predisposition doesn't mean you'll definitely develop Hashimoto's.

You can have an increased genetic risk without ever developing the condition.

And you can develop Hashimoto's without knowing of any family members with the same diagnosis.

Genetics are therefore an important part of the explanation, but not the whole story.

Why Is Hashimoto's More Common in Women?

Hashimoto's is considerably more common in women than in men.

The reasons for this difference aren't fully understood.

Researchers are investigating several possible explanations, including:

- Differences in immune system function.
- Genetic factors.
- The possible influence of sex hormones.

Several autoimmune conditions occur more frequently in women.

However, it's too simplistic to say that Hashimoto's is caused entirely by female hormones.

The development of the condition is more complicated than that.

Can Pregnancy Cause Hashimoto's?

Pregnancy and the postpartum period involve changes in the immune system and thyroid function.

Some women discover thyroid autoimmunity for the first time during or after pregnancy.

Postpartum thyroiditis may also develop after childbirth.

This is an autoimmune-related inflammation of the thyroid that can temporarily cause excessive or insufficient thyroid hormone availability.

Postpartum thyroiditis and Hashimoto's are related conditions, but they aren't exactly the same.

Pregnancy therefore doesn't automatically mean Hashimoto's was caused by becoming pregnant.

However, pregnancy and the postpartum period may be times when existing thyroid autoimmunity or a predisposition to thyroid problems becomes more apparent.

If you develop unusual fatigue, palpitations, restlessness, cold intolerance, or other persistent symptoms after childbirth, discuss whether thyroid testing is needed.

Can Stress Cause Hashimoto's Disease?

This is a question many people ask.

Perhaps your symptoms began after a difficult period.

You experienced a lot of stress, slept poorly, or spent a long time doing more than you felt able to manage.

It's understandable to wonder:

"Did that cause my Hashimoto's?"

Stress can affect sleep, mood, energy, concentration, and how you experience physical symptoms.

Researchers are also studying possible relationships between stress and autoimmune conditions.

However, there's no convincing evidence that prolonged stress alone directly causes Hashimoto's.

Experiencing stress before your diagnosis doesn't prove that stress caused your condition.

Reducing stress may support your overall health and well-being.

But you don't need to explain your diagnosis by assuming you should have relaxed more.

Can a Virus or Infection Trigger Hashimoto's?

Infections are also being studied as possible contributors to autoimmune conditions.

Researchers have proposed several ways infections might influence the immune system in people with a particular susceptibility.

However, in most cases of Hashimoto's, no specific infection can be identified as the cause.

Perhaps you had a viral illness and later developed thyroid symptoms.

That sequence doesn't automatically prove that the virus caused Hashimoto's.

The autoimmune process may have started long before the diagnosis.

That's why it's often impossible to determine exactly when Hashimoto's began.

Can Too Much Iodine Cause or Worsen Hashimoto's?

Iodine deserves particular attention when discussing thyroid conditions.

Your body needs iodine to produce thyroid hormones.

Too little iodine can cause thyroid problems.

But taking much more iodine isn't automatically better.

High iodine intake can trigger or worsen thyroid dysfunction in susceptible individuals.

Excessive iodine exposure has also been associated with thyroid autoimmunity.

That doesn't mean everyone who consumes a lot of iodine will develop Hashimoto's.

And it doesn't mean people with Hashimoto's should avoid all iodine.

The goal is adequate iodine intake without unnecessarily high amounts.

Avoid taking high-dose iodine supplements, kelp products, or large amounts of seaweed on your own in an attempt to support your thyroid.

Discuss supplements with your healthcare professional or pharmacist.

Can Gluten, Dairy, or Other Foods Cause Hashimoto's?

There's no specific food proven to cause Hashimoto's in everyone who eats it.

This includes gluten.

Celiac disease is more common among people with autoimmune thyroid conditions.

If you have celiac disease, following a strict gluten-free diet is necessary.

But that doesn't mean gluten causes Hashimoto's in everyone.

There's also no evidence that eating dairy, soy, bread, or pasta on its own causes Hashimoto's.

You don't need to look back and assume you developed the condition because you ate certain foods for years.

There's no proven diet that guarantees prevention of Hashimoto's.

And there's no reason to keep eliminating more foods without a medical need.

For most people, a varied diet remains a sensible foundation.

Can an Unhealthy Lifestyle Cause Hashimoto's?

Healthy habits matter for your overall health.

Getting enough sleep, eating a varied diet, staying appropriately active, and avoiding smoking can support your health.

But people who eat well, exercise regularly, and take good care of themselves can still develop Hashimoto's.

That's why it's not accurate to say someone developed the condition because they lived an unhealthy lifestyle.

Lifestyle can influence how you feel and certain health risks.

But that's different from proving what caused Hashimoto's.

You don't need to search for one bad habit that explains your diagnosis.

Why Are Other Autoimmune Diseases More Common With Hashimoto's?

Autoimmune conditions can occur together more frequently.

People with Hashimoto's therefore have an increased likelihood of certain other autoimmune diseases.

Examples include:

- Celiac disease.
- Type 1 diabetes.
- Autoimmune gastritis and pernicious anemia.
- Vitiligo.
- Certain other autoimmune conditions.

This doesn't mean you'll automatically develop any of these conditions.

It also doesn't mean everyone with Hashimoto's needs extensive testing for every autoimmune disease.

However, if you have symptoms that aren't adequately explained by your thyroid function, your healthcare professional may consider whether additional investigations are appropriate.

Can You Prevent Hashimoto's Disease?

Currently, there's no proven way to guarantee that Hashimoto's can be prevented.

You can't change your genetic predisposition.

And there isn't one avoidable cause responsible for every case.

Healthy living is still important.

But a healthy lifestyle can't guarantee that you'll never develop an autoimmune condition.

The same applies to supplements.

No supplement has been convincingly shown to prevent Hashimoto's in everyone.

Be especially cautious with high-dose iodine and other supplements that may affect thyroid function.

Why Can Hashimoto's Seem to Start Suddenly?

Perhaps you felt healthy for years.

And then, suddenly, you're diagnosed with Hashimoto's.

It may feel as though the condition appeared overnight.

But the time of diagnosis and the beginning of the autoimmune process aren't necessarily the same.

Thyroid autoimmunity can already be present while the thyroid still produces enough hormone.

TSH and free T4 may remain normal during that time.

Hashimoto's may only be discovered when thyroid function changes or blood tests are performed for another reason.

That's why it's usually impossible to know exactly when the autoimmune process began.

The level of your TPO antibodies doesn't tell you how long you've had Hashimoto's either.

A high anti-TPO result isn't a timeline of the disease.

Did I Cause Hashimoto's by Working Too Hard?

Perhaps you worked long hours for years.

Didn't get enough sleep.

Went through a difficult period.

Or had very little time to recover.

All of those experiences can affect how you feel.

But that doesn't mean they caused your Hashimoto's.

There's no scientific basis for concluding that one person's Hashimoto's was caused by working too hard or not resting enough.

Your diagnosis isn't proof that you did something wrong.

What may help now is considering how to support your energy, health, and any treatment you need.

Why Did I Get Hashimoto's When Someone Else Didn't?

This may be the hardest question.

Sometimes, risk factors can be identified.

Perhaps Hashimoto's runs in your family.

Maybe you have another autoimmune condition.

Or perhaps your diagnosis happened during a period when your thyroid was being monitored more closely.

But even then, we usually can't explain exactly why you developed Hashimoto's while someone else with similar circumstances didn't.

That uncertainty can be frustrating.

Still, it's more medically accurate than blaming one event without evidence that it caused the condition.

What Causes Hashimoto's? Key Things to Remember

Hashimoto's is an autoimmune condition affecting the thyroid gland.

Genetic susceptibility plays an important role. Biological and environmental factors may also contribute to the development of thyroid autoimmunity.

However, there's usually no single identifiable cause.

Stress hasn't been proven to be an independent cause of Hashimoto's.

A specific infection usually can't be identified as the cause.

And there's no evidence that you developed Hashimoto's simply because you ate gluten, dairy, or other ordinary foods.

Excessive iodine intake may be harmful to thyroid function in susceptible individuals.

Most importantly, you don't need to spend years looking back for the moment when you supposedly did something wrong.

A much more useful question after diagnosis is:

**How is my thyroid functioning now, and what monitoring or treatment do I need?**

That's something you can work through with your healthcare professional.