A large-scale genetic study of endometriosis has been carried out to better understand its link to other inflammatory and chronic conditions.

Published in Nature Genetics, the study analysed the genomes of 60,674 women with endometriosis and 701,926 healthy controls of European, American, Australian and Japanese ancestry to elucidate the mechanism behind known links between endometriosis and other inflammatory and chronic pain conditions.

‘Using different datasets of women with and without endometriosis, some of which had unprecedented detailed data on surgical findings and pain experience collected using standardised criteria, allowed us to generate a treasure trove of new information about genetically driven endometriosis subtypes and pain experience’ said Dr Nilufer Rahmioglu, first author of the study and senior researcher at the Wellcome Centre for Human Genetics, Oxford.

Endometriosis is characterised by the abnormal overgrowth of the lining of the uterus, the endometrium, in other parts of the body, such as the ovaries. Symptoms usually consist of severe pain, irregular periods, fatigue, nausea, and infertility. The exact cause of this condition is unknown, and available treatments are only used to manage symptoms. It affects five to ten percent of women around the world.

The scientists have identified 42 genetic loci linked to increased risk of endometriosis by conducting a genome-wide association study on participants of European ancestry.

Data used was largely from the UK BioBank or provided by online direct-to-consumer testing site 23andMe.com. These loci are the site of a range of genes that were differently expressed in the endometrium and therefore had a likely role in disease development. Using the large amount of genetic information gathered from this group, the researchers identified variants on these loci that are more frequently found in endometriosis patients.

Many of the genes present at the loci identified are linked to hormone maintenance as well as to 11 chronic pain conditions, such as migraine and chronic back pain. An association was also found between endometriosis and two inflammatory conditions – osteoarthritis and asthma.

This suggests a correlation between endometriosis, chronic inflammatory or pain conditions and possibly even perception of pain. The study also found that ovarian endometriosis has a distinct genetic profile, as opposed to other subtypes of the condition.

‘Endometriosis is now recognised as a major health issue affecting women’s lives’, said the co-author of the study Professor Krina Zondervan from the University of Oxford. ‘It has provided a wealth of new knowledge on the genetics underlying endometriosis, which will help the research community in their efforts to come up with new treatments and possibly new ways of diagnosing the disease benefiting millions of women worldwide.’