Approximately 80% of reproductive-aged women develop uterine fibroids —non-cancerous tumors that grow in the uterus — yet it’s often unclear what causes them.
Scientists have long suspected that genetics play a role, as do hormones, diet and major life stressors. New research from scientists at Northwestern University suggests that chemicals we’re exposed to in everyday life may also contribute to the development of uterine fibroids in many women.
According to the report, these chemicals — which are found in plastics used in food packaging, medical products (like IV bags, for example), and cosmetics — disrupt endocrine function and can lead to the growth of hormone-sensitive tumors like uterine fibroids. Even though these chemicals are toxic and can directly harm human tissue when ingested or inhaled, they are permitted in the United States and used commonly and frequently.
Past research has identified a link between endocrine-disrupting chemicals and uterine fibroids and other hormone-sensitive health conditions like breast cancer and endometriosis. But this report, published on Monday in the Proceedings of the National Academy of Sciences, is one of the first to identify how these chemicals impair hormone function.
“Currently unbanned environmental pollutants, called phthalates, cause significant reproductive problems including the growth of uterine fibroids using stimulating distinct molecular pathways in these tumors,” corresponding study author Dr. Serdar Bulun, chair of the department of obstetrics and gynecology at Northwestern University Feinberg School of Medicine and a Northwestern Medicine physician told HuffPost.
For the study, the researchers measured the amount of DEHP – the most commonly used endocrine-disrupting phthalate — in the urine of 712 participants. According to the report, we are constantly exposed to DEHP through medical products, food, drinks and dust that hangs in the air.
The team found that those with higher levels of DEHP traces in their urine had a greater risk of having a symptomatic uterine fibroid. Every 10% increase in phthalate concentration was associated with a 6% higher risk of fibroid development.
The researchers also explored why phthalates affect fibroid growth by exposing cells from some of the patients’ fibroid tumors to various types of phthalate metabolites or the substances that are leftover after phthalates are metabolized in the body.
They found that high doses of phthalates activated a hormone pathway that helped fibroid cells survive and expand. “We detected the phthalate DEHP and its breakdown products in much higher quantities in the urine of women who also have symptomatic uterine fibroid tumors. Then we asked the question of whether this association was causal. And the answer was yes,” Bulun said.
What we know about endocrine-disrupting chemicals and our health
Past research has associated endocrine-disrupting chemicals with uterine fibroids, suggesting that the higher the phthalate concentration in the body is, the greater the risk of uterine fibroids. Evidence has also linked these types of chemicals to breast cancer, endometriosis, ovarian aging, and decreased sperm production and function, Bulun said.
Scientists have suspected that phthalates facilitate fibroid cell growth by mimicking or blocking estrogen and progesterone production — two hormones that stimulate fibroid growth in people’s reproductive years — but the evidence has been limited. According to Shannon Whirledge, an associate term professor of Obstetrics, Gynecology and Reproductive Sciences at Yale School of Medicine, our understanding of how endocrine-disrupting chemicals can impact our health is in its infancy.
But these new findings shed some light on how toxins in our environment change some of our hormonal processes and contribute to the development of uterine fibroids and other reproductive health conditions. “Because the way uterine fibroids develop and grow is not well-understood, this new study is certainly important to uncovering the potential mechanisms by which a woman’s environmental exposures may increase her risk for uterine fibroids,” Whirledge said.
Unfortunately, though commonly-used chemicals are tested for toxicity, their ability to mess with endocrine function is not closely examined, mainly because the health effects can be tricky to evaluate. “The effects aren’t always related to dose, and sometimes big effects are seen at low or high doses, and the effects of endocrine disruptors are not always immediately apparent,” Whirledge said, adding that it’s clear they can significantly alter our health throughout our lifespan.
“This new study is certainly important to uncovering the potential mechanisms by which a woman’s environmental exposures may increase her risk for uterine fibroids.”
– Shannon Whirledge, associate term professor of Obstetrics, Gynecology & Reproductive Sciences
Should we avoid certain products?
It’s worth considering, according to Bulun. He recommends avoiding plastic bottles and plastic food packaging — opt for glass containers when possible and avoid polyvinyl chloride (PVC)-containing products packed with phthalates.
It’s a bit harder to completely dodge phthalates since they’re everywhere. “These chemicals are included in hundreds of different products, and in most cases, they won’t be listed on the product packaging labels,” Whirledge said. Bulun recommends carefully checking the ingredients in any foods, makeup or household products that you use. Look for microwave-safe containers, toys and consumer products that are labeled phthalate-free. Because so many medical products contain high levels of phthalates, it may be worth asking your healthcare provider if they have any phthalate-free options.
The best way to effectuate change — build public awareness. Think back to the case of BPA: growing evidence and public pressure eventually pushed legislators to ban the substance from being used in certain products like baby bottles.
The same can, hopefully, happen with phthalates, according to Whirledge. “The study from Dr. Bulun’s group is a great step towards building that foundation of research needed to understand how phthalate exposure can impact health and disease risk so that women can advocate for safer products,” Whirledge said.