Infections with the cancer-causing human papilloma virus (HPV) were more than twice as common in ovaries of women with endometriosis compared to those without the disease, suggesting that an infection may trigger the abnormal growth of endometrium outside the uterus.
Researchers suspect that inflammatory reactions and changes in the immune system during a viral infection may contribute to the disease.
Researchers at Isfahan University of Medical Sciences in Iran analyzed tissue from 50 women with endometriosis and 49 women without the disease (the control group). Since the tissue samples were part of the pathology archives, a pathologist first examined the tissue to make sure that the endometriosis diagnosis was correct.
HPV virus is the most common sexually transmitted infection. And while not causing any harm in the majority of cases, certain high-risk virus types can cause cervical and other types of cancer if the infection persists.
An analysis showed that high-risk HPV virus types were found in 13 ovaries affected by endometriosis, amounting to 26 percent. In contrast, researchers detected high-risk HPV in only five ovaries, or 10.2 percent, of the control group.
The two groups did not differ in age, the number of completed pregnancies, or the rates of cervical cancer in first-degree relatives — differences that might have explained a higher infection rate in the endometriosis group.
Since married women tend to have both more HPV infections and more endometriosis than single women, the team also looked at this factor. More women were single in the control group, but the difference did not reach statistical significance.
Although the findings do not support the idea that the viral infection directly causes endometriosis, researchers believe it can contribute to making the endometrium more inclined to become invasive.
Endometriosis is also linked to a higher risk for certain cancers, and the findings might suggest that there is a link between HPV infection, endometriosis, and cancer. But so far, there is little proof that this is really the case.
Researchers had previously suggested that infections may trigger endometriosis, and HPV has been examined in a similar manner twice. One of the studies came to the same conclusion as the Iranian team, while the other found no evidence that HPV was involved in the development of endometriosis.