Women are more likely to develop endometriosis if they have elevated levels of cadmium in their system, a new study reports.
Twice as many women with slightly or moderately elevated levels of the toxic element wound up with endometriosis compared to women with the lowest levels, researchers say.
“Although endometriosis is estimated to affect 1 in 10 women, the reason why this condition develops in some women and not in others remains unclear,” said senior researcher Kristen Upson, an assistant professor of epidemiology and biostatistics at Michigan State University.
“Our research on environmental contaminants and finding of an association between cadmium exposure and endometriosis is helping to move the needle closer to understanding risk factors for endometriosis,” she added.
This newly discovered association between endometriosis and cadmium is “a good starting point for additional studies that look at other environmental factors and how they can perhaps cause endometriosis,” said Dr. Susan Khalil, director of the Division of Sexual Health in the Raquel and Jaime Gilinski Department of Obstetrics, Gynecology and Reproductive Science at Mount Sinai.
“I think it doesn’t give exact recommendations for action at this time, or things that you can translate into clinical management. So I can’t really make recommendations off of this for patients,” Khalil added. “But I would at the same time say it’s great they’re finding these associations, so they can do high quality prospective trials to look at the role of the environment on endometriosis – and not just its impact on fertility, but also the chronic pain it causes.”
Endometriosis occurs when tissue similar to the inner lining of the uterus — the endometrium — starts to grow on other parts of the body, such as the bladder, intestines, diaphragm and other organs and structures of the female reproductive system.
These areas can develop into cysts, lesions and scar tissue, causing severe pain and fertility problems. Because the endometrial tissue responds to hormone changes, it can become inflamed during a woman’s menstrual cycle.
For this study, Upson and her colleagues analyzed survey and health data gathered by the U.S. Centers for Disease Control and Prevention on 1,750 U.S. women ages 20 to 54 between 1999 and 2006.
They specifically looked at the women’s cadmium levels because prior research has shown the toxic metal can act like the hormone estrogen, said lead researcher Mandy Hall, a data analyst in the Michigan State University Department of Epidemiology and Biostatistics.
“As estrogen plays a key role in the development of endometriosis, we were interested in seeing if exposure to cadmium was associated with a history of being diagnosed with endometriosis,” Hall said.
Researchers organized the women into four groups (quartiles) based on the cadmium levels found in their urine, from lowest to highest.
“We observed that those with cadmium levels in the second and third quartile, compared to those with cadmium levels in the first quartile, had twice the prevalence of endometriosis,” Hall said.
However, those with cadmium levels in the fourth quartile — the highest — only had a 60% increased prevalence of endometriosis compared to those with cadmium levels in the first quartile, the researchers noted.
“It is important to remember that endocrine-disrupting chemicals, like cadmium, can produce different biologic effects at different levels of exposure, and not necessarily follow a dose-response relationship of more exposure being associated with more disease,” Upson explained.
U.S. women are commonly exposed to cadmium by breathing in cigarette smoke, Hall said.
Cadmium is found naturally in the environment, but it also is released by industrial processes like smelting and burning fossil fuels or municipal waste, according to the CDC. Cadmium is used in metal plating, producing pigments, making batteries and crafting plastic products.
“With industrial activities, cadmium is released into the environment and enters soil and water,” Upson said. “Cadmium in soil and water can accumulate in plants and organisms, contaminating the food supply. Cadmium has been found in leafy greens like spinach and lettuce, as well as potatoes, grains, nuts, organ meat and shellfish.”
She said further research is needed to confirm these findings.
“However, activities that promote overall health — such as not smoking and eating a balanced diet — can help reduce exposure to cadmium, as well as to other environmental contaminants,” Upson said.
The study was published July 24 in the journal Human Reproduction.
SOURCES: Kristen Upson, PhD, MPH, assistant professor, epidemiology and biostatistics, Michigan State University, East Lansing; Mandy Hall, MS, data analyst, epidemiology and biostatistics, Michigan State University; Susan Khalil, MD, director, Division of Sexual Health, Raquel and Jaime Gilinski Department of Obstetrics, Gynecology and Reproductive Science, Mount Sinai, New York City. Human Reproduction, July 24, 2023
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