Most of us grow up learning the basics of the body — the heart, the lungs, the stomach, maybe even a bit about the immune system.
But the endocrine system?
That’s usually glossed over, if it’s mentioned at all.
Which is strange, because this quiet, behind-the-scenes system plays a role in almost everything that makes us feel human — how we grow, sleep, reproduce, respond to stress, regulate energy, and maintain balance over time.
So before we talk about endocrine disruption — and before we ask whether chemicals like glyphosate-based weedkillers might interfere with hormones — it helps to slow down and understand what the endocrine system actually is.
Not with jargon.
Not with a biology degree.
Just the fundamentals most of us were never taught.
What Is the Endocrine System?
One way to think about the endocrine system is as the body’s long-distance messaging network.
Your nervous system works fast. It sends electrical signals — more like quick shouts — to help you react in real time.
Hormones work differently. They’re chemical messengers, released into the bloodstream and carried throughout the body. Slower. Quieter. More like letters being delivered.
These messages are produced by a collection of small but powerful glands — including the pituitary, thyroid, adrenals, pancreas, ovaries, and testes. Each gland releases specific hormones that tell cells what to do, when to do it, and how strongly to respond.
If the nervous system keeps you alive moment to moment,
the endocrine system helps keep everything in balance over the long term.
Why does the endocrine system matter so much?
Because hormones influence far more than most people realise.
They help regulate how fast your metabolism runs, when you feel hungry or full, how your body responds to stress, and how well you sleep. They guide growth and development, shape fertility and sexual maturation, influence mood and memory, and play a role in immune function and bone health.
When hormonal signals are working smoothly, the body tends to feel steady and resilient.
When those signals are disrupted, the effects can be subtle at first — fatigue, mood changes, cycle irregularities — or much more pronounced, depending on timing and context.
How Hormones Work: Tiny Signals, Big Effects
Here’s one of the most misunderstood aspects of hormones:
They don’t need big changes to create big outcomes.
Hormones operate at extraordinarily low concentrations — sometimes measured in parts per trillion. At that scale, even a very small interference can alter development, metabolism, fertility, or disease risk.
A common analogy used by researchers is this:
adding a teaspoon of salt to an Olympic-sized swimming pool.
That’s the level of precision the endocrine system relies on.
This is also why chemicals that interfere with hormones can cause concern even when they don’t behave like traditional “toxins” in the usual sense.
So what is an endocrine disruptor?
An endocrine disruptor is generally defined as a chemical that interferes with the normal functioning of the hormonal system.
That interference can take many forms. A substance might mimic a natural hormone, block one, alter how hormones are produced or transported, change how sensitive cells are to hormonal signals, or disrupt the timing of hormone release — especially during critical stages of development.
The disruption doesn’t have to be dramatic.
It doesn’t have to shut the system down.
Sometimes it only needs to slightly change how a signal is sent or received.
That subtlety is exactly what makes endocrine disruption both difficult to study and deeply contested.
Why Timing Matters More Than Dose in Endocrine Disruption
One of the key insights to emerge from endocrine research is that when exposure happens can be just as important — if not more important — than how much exposure occurs.
Periods like pregnancy, infancy, childhood, and puberty are windows of intense hormonal signalling. During these stages, even small disruptions can have long-lasting or permanent effects.
Research has shown that early hormonal interference can influence sexual development, brain development, metabolic programming, immune function, and susceptibility to certain diseases later in life.
This is why questions around endocrine disruption become especially relevant when we talk about low-level, everyday exposures — including those that may occur through food, water, or environmental contact.
It’s also why the issue keeps resurfacing in discussions about residues in products like milk, cereals, honey, and bread — the very foods No More Glyphosate NZ has been independently testing.
Why regulators struggle with endocrine disruption
Most chemical regulation systems, including those used in New Zealand, were built around traditional toxicology models.
These models tend to assume that higher doses cause greater harm, that there is a clear threshold below which no effects occur, and that absence of obvious toxicity means absence of risk.
Endocrine disruption doesn’t always follow those rules.
Some hormone-active chemicals show what scientists call non-monotonic dose responses — where low doses can cause effects, higher doses may not, and different effects can appear again at higher levels.
That complexity doesn’t fit neatly into existing regulatory frameworks. And when systems aren’t designed to see something, it’s easy for it to be missed.
This regulatory blind spot is something we’ll return to later in the series.
Why the Endocrine System Matters in Discussions About Glyphosate
Quite a lot, actually.
It’s difficult to assess claims about glyphosate and hormonal health — from fertility to cancer risk to developmental timing — without first understanding how sensitive and finely tuned the endocrine system really is.
Once you understand how hormonal messaging works, the next questions come naturally.
Can chemicals interfere with those messages?
If so, how would we detect it?
And are our current testing systems equipped to notice when it happens?
Why Understanding the Endocrine System Comes First
The endocrine system isn’t fragile in the sense of being weak — but it is precise, delicately balanced, and highly dependent on timing.
Understanding that system is the first step in making sense of the broader conversation around endocrine disruption.
In the next article in this series, we’ll look more closely at what the science actually says about glyphosate and hormonal interference — and why that evidence has become one of the most contested areas in chemical safety research.
Part of The Endocrine Disruption Series: Understanding Hormones in a Chemical World
This article is part of The Endocrine Disruption Series, a four-part exploration of what the endocrine system is, how delicate it really is, and what happens when glyphosate-based weedkillers and other modern chemicals interfere with the body’s hormonal messaging system.
1. What Is the Endocrine System? (You’re here)
A simple guide to hormones, how they work, and why even tiny shifts can matter.
2. Is Glyphosate an Endocrine Disruptor?
We examine what the science actually shows — from human cells to wildlife.
3. What Endocrine Disruption Means for People, Animals, and the Environment
The real-world consequences beyond the lab.
4. Why Regulators Miss Glyphosate’s Endocrine Risks
How outdated testing frameworks keep New Zealand in the dark.
Resources & References
Most of what we’ve been taught about hormones is oversimplified. We’re told they operate like on/off switches, rising and falling in neat, predictable ways. But once you start reading the science, a different picture emerges — one where tiny shifts matter, timing matters even more, and chemicals we’ve been told are “safe” have the ability to whisper into the body’s communication system in ways we rarely measure.
If you’d like to explore this further — or see why scientists around the world are raising red flags — these resources are a good place to start.
Internal Articles (NoMoreGlyphosate.nz)
Glyphosate and Hormone Disruption — What We Know So Far
A clear, accessible overview of the emerging science linking glyphosate-based weedkillers to hormonal disturbances, including fertility, thyroid, and metabolic effects.
URL: https://nomoreglyphosate.nz/glyphosate-hormone-disruption/
Glyphosate and Male Fertility: What the Science Is Telling Us
A deep dive into animal and human studies showing reduced sperm quality, disrupted testosterone balance, and testicular effects linked to glyphosate exposure.
URL: https://nomoreglyphosate.nz/glyphosate-male-fertility/
Glyphosate in NZ Honey: First Test Results
Independent testing showing glyphosate residues in NZ honey — a real-world example of chemical exposure relevant to endocrine risk.
URL: https://nomoreglyphosate.nz/glyphosate-in-nz-honey-first-test-results/
Glyphosate in Weet-Bix and Other Cereals
Your NZ-based cereal and grain testing results, reinforcing why endocrine-disrupting chemical exposure through food matters.
URL: https://nomoreglyphosate.nz/weet-bix-glyphosate-test-results/
Scientific & Educational Resources
Endocrine Society — Endocrine Disrupting Chemicals Fact Sheet
A trusted, plain-language explanation from the world’s leading endocrine authority, covering how hormones work and why endocrine disruptors matter.
URL: https://www.endocrine.org/patient-engagement/endocrine-library/edcs
World Health Organization (WHO) & UNEP — “State of the Science of Endocrine Disrupting Chemicals”
The landmark global review explaining how endocrine disruption works, why timing matters more than dose, and how chemicals interfere with hormonal systems.
URL: https://www.who.int/publications/i/item/9789241505031
National Institute of Environmental Health Sciences (NIEHS) — Endocrine Disruptors Overview
A reader-friendly summary of endocrine disruptors, how they affect development, fertility, and metabolism, and why low-dose exposure is concerning.
URL: https://www.niehs.nih.gov/health/topics/agents/endocrine
Peer-Reviewed Research on the Endocrine System & Low-Dose Effects
Vandenberg et al. (2012) — “Hormones and Endocrine-Disrupting Chemicals: Low-Dose Effects and Nonmonotonic Dose Responses”
A foundational scientific paper showing why traditional toxicology misses endocrine effects — crucial context for understanding glyphosate debates.
URL: https://doi.org/10.1210/er.2011-1050
Gore et al. (2015) — “EDCs and Developmental Origins of Health and Disease”
Explains how exposure during pregnancy, infancy, and puberty can have lifelong effects on fertility, metabolism, and cancer risk.
URL: https://doi.org/10.1210/er.2015-1093
Diamanti-Kandarakis et al. (2009) — “Endocrine-Disrupting Chemicals: An Endocrine Society Scientific Statement”
A comprehensive review outlining the mechanisms and health impacts of endocrine-disrupting chemicals, including reproductive and metabolic effects.
URL: https://doi.org/10.1210/er.2009-0002
Glyphosate-Specific Endocrine Research (Foundational Studies)
Thongprakaisang et al. (2013) — “Glyphosate Induces Human Breast Cancer Cell Proliferation via Estrogen Receptors”
A pivotal study showing glyphosate can act like estrogen in human cells — one of the earliest endocrine red flags.
URL: https://pubmed.ncbi.nlm.nih.gov/23756170/
Gasnier et al. (2009) — “Glyphosate-Based Herbicides Are Toxic and Endocrine Disruptors in Human Cell Lines”
Early evidence that Roundup formulations disrupt aromatase (a key hormone enzyme) at extremely low doses.
URL: https://www.sciencedirect.com/science/article/abs/pii/S0300483X09003047
Romano et al. (2010) — “Prepubertal Exposure to Commercial Glyphosate Formulation Alters Testosterone Levels and Testicular Morphology”
A widely cited animal study demonstrating that early-life exposure to a glyphosate-based herbicide reduced testosterone levels and caused structural changes in developing testes — strong evidence of endocrine disruption.
URL: https://pubmed.ncbi.nlm.nih.gov/20012598/
Environmental Endocrine Disruption
Howe et al. (2004) – “Toxicity of Glyphosate-Based Pesticides to Four North American Frog Species”
Demonstrates that glyphosate-based formulations can be highly toxic to developing amphibians and discusses their potential as endocrine disruptors, given frogs’ reliance on thyroid hormones for development.
URL: https://pubmed.ncbi.nlm.nih.gov/15352482/
Taken together, these studies tell a story our regulatory system has never truly confronted: endocrine disruption isn’t about high doses, dramatic poisonings, or immediate symptoms. It’s about subtle interference. It’s about long-term patterns. And it’s about what happens when a chemical touches the body at the exact moment a developing organ, gland, or brain circuit is trying to form.
The science is there. The question now — uncomfortable as it is — is whether we’re willing to look at it.
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