Low Drive, Brain Fog, Feeling Flat: Is It Oestrogen or Testosterone?
If you have ever found yourself Googling things like:
Why do I feel so flat lately?
Where has my motivation gone?
Why do I have brain fog when my blood tests are “normal”?
Is this hormones, or is it just me?
Let’s start here.
You are not imagining it. And you are definitely not alone.
At See Her Thrive, we work with women every day who are capable, committed, and deeply invested in their work, yet quietly struggling with low drive, brain fog, and a sense of disconnection from themselves. Many are navigating PMDD, perimenopause, hormonal contraception, or HRT. Many are being told everything is “fine”.
But it rarely feels fine.
One of the most misunderstood pieces of this puzzle is the relationship between oestrogen and testosterone. They are often talked about as if they are opposing forces, locked in a hormonal tug of war.
They are not.
The reality is more nuanced and, once you understand it, far more helpful.
The short answer
Oestrogen and testosterone do not cancel each other out.
They work in relationship.
They influence how available each hormone is in the body, and how clearly those signals are received. Together, they shape how you feel day to day, particularly under pressure, stress, and change.
When this communication falters, women are often left feeling flat, foggy, less confident, or unlike themselves. Too often, the explanation offered is personal rather than biological.
A more helpful way to think about hormones is as an orchestra, not a seesaw.
When one section is too loud, too quiet, or out of sync, the whole piece feels off, even though every musician is technically still playing.
Why women need testosterone too
One of the most persistent myths in women’s health is the idea that hormones are neatly divided by gender. That oestrogen belongs to women, and testosterone belongs to men.
In reality, testosterone is essential for women. It plays a far greater role in how we feel, think, and function than most people are ever told.
In female bodies, testosterone supports motivation, confidence, mental clarity, cognitive resilience, libido, and physical strength. It influences how we show up at work, how we set boundaries, and how steady we feel in ourselves.
Many women describe feeling flat or apathetic, or as though they have lost their edge.
This is often framed as burnout, stress, or mindset.
Very often, it is a hormonal signalling issue. Testosterone is part of that picture, whether or not it has ever been mentioned in a GP appointment.
How oestrogen can affect testosterone availability
This is where things get more subtle, and where a lot of confusion comes from.
Oestrogen increases the production of a protein called Sex Hormone Binding Globulin, often shortened to SHBG.
SHBG binds to hormones in the bloodstream, including testosterone.
Why this matters
Testosterone exists in two forms:
Total testosterone, which many blood tests measure
Free testosterone, which your brain, muscles, and nervous system can actually use
When SHBG is high:
Testosterone becomes bound
Free, usable testosterone drops
Symptoms appear, even if levels look “normal” on paper
So you can have normal total testosterone, but low usable testosterone, and still feel foggy, flat, tired, or disconnected.
This pattern is especially common in:
Perimenopause
People on the combined oral contraceptive pill
Women using oestrogen HRT
Importantly, this is not oestrogen reducing testosterone production.
It is reducing access to it.
When testosterone converts into oestrogen
The relationship goes both ways.
Testosterone can be converted into oestrogen via an enzyme called aromatase.
Aromatase activity increases when:
Body fat is higher, as fat tissue produces aromatase
Chronic stress and inflammation are present
Blood sugar regulation is under strain
In these cases, testosterone may be produced normally, but rapidly converted into oestrogen and never fully doing its job.
This can create a confusing mix of symptoms:
Heaviness, bloating, and emotional overwhelm, often associated with oestrogen dominance
Alongside low drive, low motivation, and low spark, often linked to reduced testosterone effects
It is not an either or situation.
It is imbalance.
Why ratios matter more than numbers
One of the most common frustrations we hear is: “My tests are normal, but I do not feel normal.”
Hormones do not act in isolation. Your body experiences them in relationship.
Oestrogen may be in range, but testosterone may be too low relative to it. Testosterone may be normal, but SHBG may be so high it cannot be used. Fluctuating oestrogen, which is very common in perimenopause, can destabilise testosterone signalling even further.
This is why so many women say, “I am not depressed. I just do not feel like myself anymore.”
That experience deserves explanation, not dismissal!
The perimenopause effect
Perimenopause changes the entire hormonal conversation.
Oestrogen becomes erratic, sometimes surging high and then crashing low, while testosterone tends to decline more gradually over time.
This creates:
Hormonal mismatch
SHBG fluctuations
Increased nervous system instability
Many women describe losing confidence, feeling less resilient, experiencing reduced drive and motivation, and developing increased self doubt at work.
These experiences are often treated as personal or professional issues.
They are biological shifts.
What this means for you (especially if you’re on HRT)
If you’re in perimenopause or menopause and already using HRT, this part matters.
For many women, oestrogen-based HRT can be genuinely life-changing. Hot flushes ease. Sleep improves. Mood stabilises.
But some women reach a point where they think:
“I’m on HRT… so why do I still feel flat?”
“Why is my drive still low?”
“Why does my confidence feel muted?”
“Why do I feel better, but not like myself?”
This is where testosterone often becomes the missing piece in the conversation.
Oestrogen HRT can increase SHBG, which can reduce how much testosterone your body can actually use. So even though oestrogen symptoms improve, drive, motivation, confidence, and mental clarity may not fully return.
This does not mean your HRT has failed.
And it does not mean you need to stop what you’re doing.
It means the picture may be incomplete.
For some women, particularly those who still feel flat or disconnected on oestrogen HRT alone, it can be helpful to ask whether testosterone has been considered, measured, or discussed as part of their care.
Not as a fix-all.
Not as a quick win.
But as part of a fuller, more honest conversation about hormone balance, ratios, and how you actually feel in your body.
This is especially relevant if:
Your menopause symptoms have improved, but your drive or spark has not
You feel emotionally steadier, but mentally flatter
Your blood tests look fine, yet something still feels off
The goal is not optimisation or perfection.
It’s feeling more like yourself again.
A more useful question
Instead of asking, “Is my oestrogen too high or is my testosterone too low?”
Try asking, “How well are my hormones communicating, and how much usable hormone do I actually have?”
That shift alone can be deeply relieving.
Final thought
At See Her Thrive, we are not interested in telling women to push through, optimise harder, or accept feeling less like themselves as the cost of success.
Hormonal health is not about chasing perfect numbers.
It is about balance, communication, context, and respect for the realities of women’s bodies, particularly at work.
If you have been told everything is “normal” but your lived experience says otherwise, that matters.
Your body is not broken.
It is giving you information.
Join us live
If this article has you thinking, “Okay, this is me,” and you want practical, hormone literate support without the panic, the doom scrolling, or the feeling that you need to overhaul your whole life, come and join us.
Perimenopause without the Panic is our live virtual workshop designed to help you understand what is happening in your body, make sense of the symptoms, and feel more steady and supported in day to day life and work.
If you want to learn more, join us on 17 March for our live virtual workshop.