The Biggest Triggers That Can Flare Hashimoto's (And What You Can Do About Them)

24 July

When you're diagnosed with Hashimoto's, one of the first questions you're likely to ask is:

"Why did this happen?"

While genetics certainly play a role, genes alone don't "pull the trigger".

Many people carry the genes associated with Hashimoto's but never develop the condition. More often, it's a combination of genetic susceptibility and environmental triggers that causes the immune system to begin attacking the thyroid.

The good news? While we can't change our genes, we can often reduce many of the triggers that continue to fuel the autoimmune process.

Here are some of the most common triggers I see in clinical practice.

1. Chronic Stress

Stress is one of the biggest contributors to autoimmune disease.

Your body doesn't distinguish between emotional stress, lack of sleep, overtraining, financial pressure, yoyo dieting or caring for young children—it all activates the same stress response.

When stress becomes chronic, cortisol regulation changes, inflammation increases, and immune function becomes dysregulated. This can make autoimmune activity more likely and may contribute to Hashimoto's flares.

Many women tell me their thyroid symptoms seemed to begin after a significant stress like:

A difficult pregnancy or birth
A divorce or relationship breakdown
Caring for ageing parents
Burnout at work
Months (or years) of poor sleep

While stress isn't the sole cause of Hashimoto's, it can certainly be the tipping point.

2. Blood Sugar Instability

Blood sugar has a surprisingly powerful influence on the immune system.

Frequent spikes and crashes in blood glucose increase inflammation and place extra demand on the adrenal glands. Over time, this can worsen fatigue, anxiety, brain fog and thyroid symptoms.

Many women with Hashimoto's find themselves reaching for sugar or caffeine simply to get through the day—creating a cycle that's difficult to break.

Stable blood sugar creates a calmer environment for both your hormones and your immune system.

3. Gut Health Problems

Around 70% of the immune system is associated with the gut, making digestive health an important part of autoimmune management.

Poor gut health may contribute to increased intestinal permeability ("leaky gut"), allowing larger food particles and bacterial components to enter the bloodstream. This can increase immune activation.

Gut issues are common alongside Hashimoto's and other autoimmune conditions.

Supporting digestion, improving the gut microbiome and reducing inflammation can all be valuable pieces of a comprehensive Hashimoto's treatment plan.

4. Nutrient Deficiencies

The thyroid is heavily reliant on nutrients to produce hormones and regulate immune function.

Some of the nutrients commonly found to be low in people with Hashimoto's include:

Selenium
Zinc
Iron
Vitamin D
Magnesium

Low thyroid function can also reduce nutrient absorption, creating a frustrating cycle where deficiencies continue to worsen symptoms.

Rather than guessing, appropriate testing can help identify where support is needed.

5. Hormonal Changes During Perimenopause

This is a major problem time…. Perimenopause is a time when many women first notice their thyroid symptoms worsening—or when Hashimoto's is diagnosed.

As oestrogen and progesterone fluctuate, the immune system also becomes more reactive.

At the same time:

Sleep often becomes poorer.
Stress resilience declines.
Blood sugar becomes less stable.
Inflammation tends to increase.
Weight becomes harder to manage.

It's no surprise that Hashimoto's often becomes more noticeable during this life stage.

Supporting hormones, nervous system health and metabolic function together often produces much better outcomes than focusing on the thyroid alone.

6. Infections and Significant Illness

For some people, symptoms appear after a viral illness, glandular fever, COVID-19 or another significant infection.

Infections can temporarily activate the immune system, and in genetically susceptible individuals this heightened immune response may contribute to autoimmune disease becoming clinically apparent. Some viruses even hide in follicular cells of the thyroid, blocking ability to make thyroid hormone.

This doesn't mean every infection causes Hashimoto's—but viral load or infections can sometimes be one of several contributing factors.

Remember: It's Rarely Just One Thing

One of the biggest misconceptions about Hashimoto's is that there's a single cause. In reality, it's usually an accumulation of multiple factors over many years.

Perhaps you've experienced years of chronic stress. Your gut health has been struggling. Your iron and vitamin D have slowly declined. Now you've entered perimenopause….

Individually, none of these factors may have caused Hashimoto's. Together, however, they can create the perfect environment for the immune system to become overactive.

That's why, as a naturopath, I never look at the thyroid in isolation.

Instead, I look for the patterns.

By addressing the drivers behind the immune dysfunction—not just replacing thyroid hormone where necessary—we can often help reduce inflammation, support energy, improve symptoms and help your body function more efficiently.

Hashimoto's isn't simply about your thyroid. It's about understanding why your immune system became dysregulated in the first place—and supporting your whole body back towards balance.

Natasha Gedrim (BHSc Naturopathy)

Thyroid and Hormone Naturopath