Why Menopause Can Make You Feel Low — Even When Your Blood Tests Look “Normal”
Many women enter perimenopause or menopause expecting hot flushes and irregular periods.
What often catches them off guard is the sudden shift in how their brain feels.
Many women I see are taken back when they start to notice:
Brain fog
Slower thinking
Memory lapses
Poor concentration
Reduced motivation
Anxiety and/or low mood
Fatigue that feels deeper than “just stress”
Feeling unlike themselves
Yet when thyroid blood tests are performed, they are often told everything looks “normal.”
This can be incredibly frustrating — especially for women who intuitively feel that something has changed metabolically.
What many women don’t realise is that the low-oestrogen state of menopause can significantly affect how thyroid hormones — especially biologically active T3 (triiodothyronine) — functions inside the brain, as well as the massive neurotransmitter shift that also can happen.
This is why, what your bloods are saying is only a small fraction of the story.
Menopause Changes Brain Energy Metabolism
Oestrogen plays a major role in brain health and energy production.
It helps regulate:
Glucose metabolism in the brain
Mitochondrial energy production
Neurotransmitter signalling
Blood flow to brain tissue
Neuroprotection and cognitive resilience
As oestrogen declines during menopause, the brain becomes less efficient at producing and using energy.
Research has shown, such as that in The International Journal of Gynecology and Obstetrics (Cognition in menopausal women, Khadilkar et al, 2026) menopausal women can develop reduced glucose metabolism in important brain regions, including areas involved in memory, mood and mental clarity.
This means the brain often becomes more dependent on:
Efficient thyroid signalling
Good T3 activity
Stable blood sugar
Healthy mitochondria
This is one reason menopause can suddenly “unmask” borderline thyroid dysfunction, or any other area in the body that was slightly under functioning, that may have previously gone unnoticed.
Your brain needs T3 bioactive hormone to function
T3 is the metabolically active thyroid hormone that helps regulate:
Mitochondrial energy production
Nerve signalling
Dopamine and serotonin activity
Mental speed and alertness
Memory and hippocampal function
But the brain does not simply rely on how much T3 appears in the bloodstream.
Brain cells also depend on:
Local conversion of T4 → T3
Transport of thyroid hormones into cells - this is a big one!
Thyroid receptor sensitivity
Cellular responsiveness to thyroid hormone
This is where menopause may create problems.
Oestrogen Influences Thyroid Hormone Sensitivity
Emerging research suggests oestrogen affects several aspects of thyroid hormone function, including:
Thyroid receptor sensitivity
Deiodinase enzymes that convert T4 into T3
Transport of thyroid hormones into cells
Mitochondrial responsiveness to T3
As oestrogen declines, some women may become less responsive to thyroid hormone at a cellular level.
Functionally, this can look like:
Adequate thyroid hormone circulating in the blood
But poorer utilisation inside cells and brain tissue
This may help explain why some women feel profoundly hypothyroid despite “normal” lab ranges.
The Brain Becomes More Metabolically Vulnerable
The menopausal transition is not only hormonal — it is metabolic.
The combination of:
Lower oestrogen
Stress and cortisol changes
Blood sugar instability
Inflammation
Mineral depletion
Reduced thyroid responsiveness
can create what some practitioners describe as a “low metabolic brain state.”
This often overlaps strongly with the symptoms women report in clinic:
Mental fatigue
Poor memory
Feeling flat or emotionally blunted
Reduced stress tolerance
Brain fog
Increased anxiety
Feeling cold or sluggish
Weight gain despite “doing everything right”
Cortisol Can Further Impair T3 Signalling
Perimenopause is often one of the most stressful stages of a woman’s life.
Many women are juggling:
Work pressures
Parenting teenagers or young adults
Ageing parents
Poor sleep
Financial stress
Relationship strain
Overtraining or under-recovery
Chronically elevated cortisol may further interfere with thyroid function by:
Reducing T4 → T3 conversion
Increasing reverse T3
Impairing thyroid receptor sensitivity
Worsening blood sugar instability
Why Symptoms Can Worsen During Menopause
A woman may technically have:
Normal TSH
Normal T4
Even normal T3
Yet still experience symptoms because:
Brain demand for thyroid hormone has increased
Cellular responsiveness has declined
Mitochondrial efficiency is lower
Stress and inflammation are interfering with signalling
This is why menopause can suddenly worsen:
Hashimoto’s symptoms
Fatigue
Brain fog
Mood instability
Weight gain
Cold intolerance
Reduced resilience and motivation
even without dramatic changes in blood tests.
One Way To Think About It
Menopause lowers the brain’s “metabolic buffer.”
So if thyroid function was already borderline, compensation becomes harder.
Final Thoughts
If you are experiencing persistent fatigue, brain fog, low mood, poor concentration or unexplained metabolic changes during menopause, it is important not to dismiss these symptoms simply because standard blood tests fall within range.
Hormones, thyroid function, stress physiology, minerals, blood sugar regulation and mitochondrial health are deeply interconnected.
Sometimes the issue is not the amount of thyroid hormone present in the blood — but how effectively the brain and body are able to respond to it.
I help women understand this connection which helps them finally feel validated, supported, and better equipped to address the underlying drivers contributing to how they feel.
Natasha Gedrim (BHSc Naturopathy)
Thyroid and Hormone Naturopath
