Poor thyroid function: the symptoms, the causes and what to do next
If you’ve been feeling exhausted, foggy, flat, and unlike yourself…
and you’ve been told your blood tests are “normal” — you are not alone.
According to the Australian Thyroid Foundation, well over 1 million Australians are estimated to be living with an undiagnosed thyroid disorder, and women are significantly more affected than men.
And in my clinic, I see this pattern all the time — especially in women moving through perimenopause.
They don’t feel like themselves anymore.
Their energy drops.
Their weight becomes harder to manage.
Their mood shifts.
Their motivation disappears.
But their thyroid tests?
“Normal.”
So what’s actually going on?
Perimenopause Is a Stress Test for Your Thyroid
Perimenopause is not just about changing hormones.
It is a phase where the body becomes more sensitive to stress, more nutrient-dependent, and less resilient overall.
During this time:
Oestrogen fluctuates significantly
Progesterone declines
Cortisol becomes more reactive
Blood sugar becomes less stable
And all of this directly impacts thyroid function.
Your thyroid does not work in isolation — it is deeply connected to your nervous system, your metabolism, your minerals, and your hormones.
When oestrogen fluctuates, it can affect how thyroid hormones are transported and used in the body.
When stress rises, it can reduce the conversion of T4 into active T3.
When blood sugar swings, it puts further pressure on thyroid signalling.
So even if your thyroid gland itself hasn’t “failed”…
your ability to use thyroid hormones efficiently can decline.
The Missing Piece: Low Thyroid Function vs “Normal” Labs
One of the biggest gaps I see in women’s health is this:
You can have thyroid hormones that fall within the “reference range”…
but still be functioning at a low level for your body.
This is can be known as ‘subclinical thyroid function’
It often looks like:
fatigue that doesn’t resolve or wiped out easily
brain fog and poor focus
weight gain or difficulty losing weight
low mood or flatness
feeling cold
reduced motivation
And it can sit quietly for years without being picked up clearly in standard testing.
Because “normal” does not always mean optimal.
Why Thyroid Function Becomes Disrupted
Thyroid issues rarely happen in isolation.
They are usually the result of multiple layers of stress on the body over time.
Here are some of the most common drivers I see:
1. Nutrient Deficiencies
The thyroid relies heavily on key nutrients to produce and activate hormones.
Low levels of these nutrients can reduce thyroid hormone production and conversion.
And during perimenopause, your demand for these nutrients increases — making deficiencies more impactful.
2. Heavy Metals and Toxic Load
Exposure to heavy metals (like mercury, lead, and excess copper) and environmental toxins can interfere with thyroid function.
They can:
block thyroid receptors
disrupt hormone signalling
increase oxidative stress
burden detoxification pathways
This creates a situation where thyroid hormones are present… but not effectively used.
3. Gut Dysfunction
Your gut plays a major role in thyroid health.
A significant portion of thyroid hormone conversion happens in the gut
Poor gut health can impair nutrient absorption
Dysbiosis can drive inflammation and immune activation
If the gut is not functioning well, thyroid function often follows.
4. Nervous System Stress
Chronic stress is one of the most underestimated drivers of thyroid dysfunction.
When the body is in a prolonged stress response:
cortisol rises
T4 → T3 conversion is reduced, as a protective mechanism
the body prioritises survival over metabolism
This leads to a slowing down of metabolic function, even if lab values appear “okay.”
5. Immune System Dysregulation
Many thyroid conditions — especially autoimmune ones like Hashimoto’s thyroiditis — involve the immune system.
During perimenopause, or any time of significant hormonal change, immune regulation can become more unstable due to:
hormonal fluctuations
increased inflammatory signalling
gut permeability
chronic stress
This can trigger or worsen autoimmune activity, where the body begins to attack its own thyroid tissue.
But even without a diagnosed autoimmune condition, low-grade immune activation can still impair thyroid function…. I’m looking at you Inflammation!
6. Genetics (and Why They’re Not the Full Story)
Yes, genetics can play a role in thyroid conditions.
But genes are not a guarantee.
They are instructions — not destiny.
For a gene to impact your health, it has to be triggered.
How are they triggered?
stress
nutrient status
toxic exposure
gut health
lifestyle patterns
fluctuating hormones
This is why two people can carry the same genetic risk… and have completely different outcomes.
Why So Many Women Feel Stuck
When you combine:
hormonal fluctuations
increased stress load
nutrient depletion
and subtle thyroid dysfunction
You get a picture where women feel:
tired, foggy, unmotivated, and stuck in their weight…
but without clear answers.
They are told:
“Everything looks fine.”
So they keep pushing through.
But the body does not respond to force — it responds to support.
The Crux
If you are not feeling like yourself right now, this is not a personal failure.
It is often a physiological shift that needs deeper support.
When we:
support thyroid function properly
stabilise blood sugar
rebuild nutrient levels
regulate the nervous system
and reduce overall load on the body
Things start to change.
Energy improves.
Clarity returns.
Weight becomes more responsive.
You feel more like yourself again.
Final Thought
Perimenopause does not create dysfunction out of nowhere.
It reveals what your body has been compensating for.
And your thyroid is often right at the centre of that picture.
If you feel like something is being missed…
it is worth looking deeper.
Because you deserve to feel well — not just be told that you are.
Natasha Gedrim (BHSc Naturopathy)
Perimenopause and Thyroid Naturopath
