Endometriosis is a puzzling and sometimes
debilitating disease that affects millions of women around the world.
Women suffering from endometriosis experience a variety of symptoms,
with lower abdominal pain being most common. Pain can be especially
intense before and during menstrual periods. Some women experience pain
throughout the menstrual cycle; some during sex. The disease forces more
than 100,000 hysterectomies each year in the United States alone, and
the costs of the disease exceed $1 billion annually.
Particularly troubling is the fact that it is showing up more than ever
before in very young women. Given the poor quality of data, however, it
is difficult to document long term trends or determine the precise
number of women afflicted with the disease. Many cases go unreported and
accurate, confirmed diagnosis requires an invasive surgical procedure.
Nonetheless, specialists in the field believe that the prevalence of the
disease has increased greatly since World War II. The National Institute
of Child Health and Human Development estimates that endometriosis
afflicts 10 to 20 percent of women of childbearing age in the U.S. Prior
to 1921, there were only twenty reports of the disease in the worldwide
Endometriosis develops when endometrial-like tissue starts growing in
places where it shouldn’t be, away from the lining of the uterus, often
in the abdominal cavity or pelvic region, but sometimes in lungs or
arms, and elsewhere. These tissue growths respond to hormonal signals in
the menstrual cycle in the same way that uterine lining does, building
up and breaking down each month. But while the uterine lining can be
flushed out of the body during menstruation, the tissue remains of
endometrial growths have no place to go. Internal bleeding, inflammation
and other problems result.
While these facts about endometriosis are clear, the causes of the
disease are much more obscure and debated. There are four key parts to
First, how does endometrial tissue wind up in inappropriate locations?
One suggestion is that endometrial cells are transported by reverse flow
off blood during menstruation into the abdominal cavity, or through the
blood stream and lymphatic system to more remote sites. Another is that
cells in the remote locations are transformed from their original
condition into endometrial cells. These explanations are not mutually
Second, why doesn’t the immune system prevent endometrial tissue from
becoming established and growing? Recent research has revealed that
women with endometriosis are also likely to experience an array of
immune system problems, suggesting that immune system dysfunction may be
the proximal cause of endometriosis. The challenge then is to understand
what has happened to the endometriosis victim's immune system.
Third, what would lead some women to develop severe endometriosis, while
others none at all? There appears to be some heriditary component to the
risk of endometriosis, possibly involving multiple genes, but
environmental factors are also implicated. The most telling evidence on
environment comes from animal studies in which dioxin increases the risk
of endometriosis in Rhesus monkeys, and also increases the likelihood
that endometrial implants will thrive in rodents. Monkeys exposed to
radiation also are more likely to develop endometriosis.
And fourth, what are the patterns of the disease over time? As indicated
above, it is widely believed that endometriosis is more common now than
mid-20th century, and data also suggest that more cases are now
developing earlier in life than before and becoming more severe.
As we describe in Chapter 10 of Our Stolen Future, the medical causes of
endometriosis are shrouded in uncertainty. A few studies completed by
the time we published OSF pointed toward contamination. Since then a
small number of studies have been reported consistent with this trend.
None contradict it.
In 1992, German scientists reported an association between heavy PCB
contamination and endometriosis that hinted at a new chapter in the
search for causes of endometriosis. Then in 1993 researchers from the
Harlow Primate Center at the University of Wisconsin published dramatic
and unexpected findings . Their study was of monkeys used in research on
the long-term reproductive effects of dioxin. When three of the dioxin
treated animals died of severe endometriosis, a new study was initiated
to compare the presence and severity of endometriosis with the animals
exposure to dioxin. The study found a dose-dependent relationship
between dioxin and endometriosis. Animals with more exposure were more
likely to develop the disease, and the greater a female monkey's
exposure to dioxin, the greater the severity of the disease. Only one of
7 animals exposed to 25 parts per trillion dioxin was free of
endometriosis. This was much higher than the rate of endometriosis
experienced in the general population of monkeys at the research center,
Experimental work has now afforded additional clues. In mice and rats,
exposure to dioxin increases the size of endometriotic sites that are
experimentally induced. A furan also promotes endometrial growth.
More about dioxin and endometriosis...
While we still lack scientific certainty about the causes of
endometriosis, exposures to environmental factors that undermine the
immune system are emerging as one of the most likely causative agents.
Both dioxin (and other dioxin-like compounds) and radiation harm immune
system action, in monkeys as well as in people. Widespread exposures to
dioxins increased during the 20th century, as most likely did
endometriosis. Other contaminants also are toxic to the immune system
including a variety of pesticides and industrial compounds.
This combination of experimental data from animals and circumstantial
evidence from people suggests that preventative steps to reduce
exposures could assist in the fight against endometriosis.