New Research Reveals Exactly How Everyday Chemicals Disrupt Your Hormones
By now, we know microplastics are bad for us. You may be trying to store leftovers in glass containers instead of plastic ones, or swapping black plastic spatulas for wooden ones—but do you actually know why these swaps matter?
Scientists have long known that many chemicals in plastic are endocrine disruptors, meaning they interfere with our body's hormonal system. But the exact mechanisms behind how they do this have remained murky. A new study published in Basic & Clinical Pharmacology & Toxicology has identified a previously unknown pathway that may finally explain part of the picture.
What the research says
Researchers looked at data from clinical trials where healthy volunteers aged 18 to 45 were given 600mg of rifampicin once daily for one week. Rifampicin is an antibiotic that is known to activate the pregnane X receptor (PXR). PXR is a protein in the body that is known for helping the liver break down foreign substances, but also plays a key role in controlling how much sex hormone-binding globulin (SHBG) your liver produces.
SHBG acts like a taxi service for sex hormones like testosterone in your blood, determining how much of those hormones are actually ‘available’ to your cells. Researchers found SHBG levels doubled in participants after a week of rifampicin.
As a result, total testosterone levels rose in male participants, but free, biologically active testosterone decreased. Researchers also saw thyroid hormones fall in male participants.
The connection to plastic
This discovery suggests that many chemicals found in everyday items, often referenced as endocrine disruptors, may indirectly influence sex hormones through this mechanism. These chemicals are known PXR activators, which this study shows leads to increased SHBG and changes in hormone levels.
“We have long known that some chemical substances can disturb the balance of sex hormones. Now we’ve identified a mechanism — a new PXR–SHBG–testosterone pathway — that explains these effects in humans,” says Dr. Janne Hukkanen in a press release for the University of Oulu, where he conducted this study.
You might be wondering where these chemicals are lingering, and the answer is unfortunately more places than you would hope. PXR disruptors are found in items like pesticides, flame retardants and plastic additives, leading the researchers to believe the findings of this study are broadly significant.
4 ways you can reduce environmental toxins
Cutting environmental toxins out of your life may feel overwhelming, but you don’t have to overhaul your entire life. Start off with a few simple swaps from this list that feel doable for you.
- Swap out plastic kitchen tools. It’s easy for plastic to make its way into our food when we’re using it in the kitchen. Flame retardant has been found in black plastic kitchen tools1, so switching those out for wooden or silicone items is a great first step.
- Filter your water. If you are able to invest in a home water filter, this is a great way to reduce pollution in your drinking water. And if you’re more of a bottled water drinker, try to find brands that use aluminum packaging rather than plastic. way to do this or at least avoid drinking from plastic containers.
- Avoid heating up plastic containers2. Microplastics seep into food more quickly when exposed to heat, so do your best to heat up food in glass or silicone containers. This might look like transferring leftovers into a microwave-safe glass bowl before heating them up, brewing loose leaf tea instead of using a tea bag, or cooking rice from scratch instead of in a microwavable instant pouch.
- Take a second-look at personal care items and cleaning products. Avoiding cleaning products with words like "danger, warning, poison, or fatal.” is a good place to start. And lookout for personal care products that are organic, fragrance-free, phthalate-free, and paraben-free when possible. The more words you recognize on the label, the better.
What the study doesn’t say
This study has major limitations when it comes to findings related to female sex hormones. SHBG levels doubled in women just as they did in men after rifampicin, so the core finding, that PXR activation raises SHBG, held true regardless of sex.
Unlike in men, testosterone levels did not significantly change for the women in the study. Additionally, estrogen, progesterone, and other reproductive hormones were essentially unaffected.
However, the absence of significant findings in women doesn't mean nothing is happening. More likely, it is a result of the study being too small; women only made up one third of participants, and varied in whether they were pre- or post-menopausal and where they were in their menstrual cycles.
Estrogen and progesterone fluctuate dramatically across the menstrual cycle, pregnancy, and menopause, creating more windows of potential disruption. Some chemicals found in plastics have been specifically linked in other research to irregular menstrual cycles, reduced fertility3, and earlier onset of menopause. So there are significant reasons beyond this study for women to pay close attention to these chemicals.
The takeaway
Research into microplastics and their effects on human health is still in its early stages, and this study is just one piece of a much larger puzzle. But the identification of this PXR–SHBG pathway gives scientists a concrete mechanism to investigate further, and gives the rest of us one more reason to make thoughtful choices about plastic exposure in our daily lives.
You don't need to overhaul everything at once. Small, consistent swaps add up.