Endometriosis is usually discussed in relation to pelvic pain, infertility and reproductive health, but new research suggests its effects may extend further.

A large US study found that women diagnosed with endometriosis were more likely to develop type 2 diabetes, with the strongest associations seen in some younger women and certain forms of the disease.

Published in Diabetologia, the research analysed electronic health records from Utah covering a 25-year period. The findings do not prove that endometriosis causes diabetes, but they suggest that metabolic health may deserve more attention in some patients with the condition.

Nearly 3 Million Women Were Studied

Researchers led by Maggie Fuzak Nunziato and Dr Anna Pollack of George Mason University examined health records from almost 3 million women who lived in Utah between 1996 and 2021.

Nearly 100,000 women received an endometriosis diagnosis during that period.

The study used a retrospective cohort design, meaning the researchers looked back through existing medical records rather than assigning participants to different treatments. This allowed them to follow a very large population over time, although this type of research can identify associations rather than establish direct cause and effect.

Overall, women with endometriosis were 46% more likely to develop type 2 diabetes than women without an endometriosis diagnosis.

Risk Was Not Equal Across Groups

The relationship appeared stronger among women who had not yet reached menopause.

It was also more pronounced among women with a body mass index below 30 kg/m², a group that includes people who are underweight, within the healthy-weight range or overweight but not living with obesity.

That finding is notable because these women would not traditionally be viewed as the group at greatest risk of type 2 diabetes based on body weight alone.

Among postmenopausal women aged 50 or older, the association was much weaker. A correction published after the original paper clarified that the adjusted hazard ratio in this group was 1.07, meaning a comparatively modest increase in risk.

Location Of Endometriosis Mattered

The researchers also examined whether diabetes risk differed according to where endometriosis lesions were recorded.

The strongest association appeared in women whose endometriosis was classified as affecting “other sites”. This category included disease in locations outside the more typical pelvic areas, such as the gastrointestinal tract, abdominal wall or chest.

Women in this category had more than twice the risk of developing type 2 diabetes compared with women without endometriosis.

The study does not establish why location might matter. More extensive or atypically located disease could reflect differences in inflammation, disease severity or other biological factors, but those possibilities require further investigation.

Inflammation May Be One Clue

Endometriosis and type 2 diabetes are very different conditions, but both involve inflammatory processes.

In endometriosis, endometrial-like tissue grows outside its usual location, commonly around the ovaries and fallopian tubes. The condition can trigger chronic inflammation, although symptoms vary widely and some women experience few or none.

Type 2 diabetes develops when the body becomes less responsive to insulin or cannot produce enough insulin to maintain normal blood glucose levels.

The researchers suggest that shared inflammatory or metabolic pathways could potentially help explain the association, but the current study was not designed to identify a specific biological mechanism.

Gestational Diabetes Did Not Explain It

The team also looked at gestational diabetes, which develops during pregnancy and is itself associated with a greater likelihood of type 2 diabetes later in life.

Among women who had given birth, a history of gestational diabetes did not significantly change the relationship between endometriosis and later type 2 diabetes.

That suggests the association observed in the wider study was not simply being driven by pregnancy-related diabetes.

What The Findings Mean

The researchers say the results may be particularly relevant for premenopausal women with endometriosis who do not have obesity, because they may otherwise be considered at relatively low metabolic risk.

Fuzak Nunziato said the findings add to growing evidence that endometriosis may affect more than reproductive health alone.

However, the study does not mean that every woman with endometriosis will develop diabetes, nor does it show that endometriosis directly causes the condition. Electronic health records can also miss undiagnosed cases, and other factors may contribute to the observed relationship.

The practical importance lies in identifying a potentially overlooked group that could benefit from closer attention to metabolic health. Further studies will be needed to determine whether earlier screening for type 2 diabetes in selected patients with endometriosis can improve long-term outcomes.