Menopausal Hormone Therapy is having a moment.
As awareness grows around perimenopause and menopause, more and more women are being prescribed menopausal hormone therapy (MHT) to try and help their energy, cognition, sleep, and sense of self. This can be oestrogen, progesterone or both with varying success depending on the woman.
But there’s a question almost no one is asking:
What happens to these hormones after they leave the body?
Because they don’t just disappear.
The invisible pathway: from prescription to planet
When a woman takes oestrogen – whether oral or transdermal – her body metabolises it, but a proportion is excreted via urine and faeces. These hormone metabolites enter the sewage system, pass through wastewater treatment plants, and are ultimately released into rivers, lakes, and coastal ecosystems.
Here’s the problem:
Most wastewater treatment systems were never designed to remove hormones.
As a result, biologically active oestrogens – such as oestradiol and oestrone – are now routinely detected in waterways across the world.
And they are not benign.
Hormones don’t stop working just because they’re in water
Oestrogens are powerful signalling molecules. In the human body, they regulate reproduction, brain function, bone density, and more.
In the environment, they do the same thing – just not where we want them to.
Research has consistently shown that even at extremely low concentrations (parts per trillion), these compounds can:
- Disrupt endocrine systems in fish and amphibians
- Cause feminisation of male fish
- Reduce fertility and alter reproductive development
- Contribute to long-term population changes in aquatic species
This isn’t theoretical. These effects have been observed in real ecosystems exposed to treated wastewater.
The rise of MHT: a quiet environmental shift
We are now seeing a significant cultural and medical shift. More women are:
- Starting MHT earlier
- Staying on it longer
- Using bioidentical forms of oestrogen
From an individual health perspective, this can be life-changing.
But from a systems perspective, it raises an important consideration:
What happens when millions more women are contributing small, daily amounts of biologically active hormones into the water system?
Individually, the dose is tiny.
Collectively, it becomes continuous.
This creates what scientists call “pseudo-persistence” – a constant environmental presence due to ongoing input, even if the compound itself breaks down relatively quickly.
This isn’t just about HRT
To be clear, menopausal hormone therapy is not the sole – or even the largest – source of environmental oestrogens.
Other contributors include:
- The oral contraceptive pill
- Agricultural runoff from livestock
- Industrial chemicals with hormone-like effects
What matters is the cumulative load.
We are now living in a world where waterways contain complex mixtures of endocrine-disrupting compounds – oestrogens, plastics, pesticides, and more – interacting in ways we are only beginning to understand.
A One Health perspective
This is where we need to zoom out.
The emerging field of environmental health is increasingly guided by a One Health framework – the understanding that human health, animal health, and ecosystem health are deeply interconnected.
What we excrete does not vanish.
It cycles.
From body → water → ecosystem → food chain → and potentially back again.
This doesn’t mean MHT is “bad”. That’s far too simplistic – and unhelpful.
But it does mean we need to evolve our thinking.
So where do we go from here?
This is not a call to fear hormone therapy. It is a call to maturity in how we think about healthcare and the impacts our choices have on our community and environment.
Some important directions forward may include:
- Upgrading wastewater treatment technologies
Advanced processes like ozonation and activated carbon filtration can significantly reduce hormone residues. - More nuanced prescribing conversations
Considering factors like dose, delivery method, and duration – not just for symptom relief, but within a broader systems context. - Research into environmental pharmacology
We need better modelling of how rising MHT use translates into environmental load. - Educating both practitioners and patients
So we can hold both truths at once:
Hormone therapy can be beneficial and part of a larger ecological story.
The deeper invitation
As women, we are being invited into a new relationship with our hormones – one that is informed, empowered, and supported.
Perhaps the next step is expanding that awareness beyond the body.
To recognise that our biology is not separate from the environment, but intimately connected to it.
Because true health – hormonal, human, and planetary – has never been just an individual experience.
It’s a collective one.