A long-term condition, it is where small pieces of the womb lining, or endometrium, are found outside of the womb itself, either in the fallopian tubes, ovaries, bladder, bowel, vagina or rectum.
However, the symptoms vary greatly from person to person, and some women experience very few or even no symptoms at all. Left untreated though, it can cause infertility or other complications, so if you are concerned that you may be a sufferer, here's what you need to know.
The most common symptoms of endometriosis are painful or heavy periods, pain in the lower abdomen, pelvis or lower back, pain during sexual intercourse, bleeding between periods, and trouble conceiving. Discomfort during urination, bleeding from the rectum, a bowel blockage and even coughing blood can also occur.
The longer you have endometriosis, the greater the chance that fertility will be affected. That said, the NHS estimates that up to 70 per cent of women with a mild or moderate case will still be able to get pregnant once the condition is being treated.
Further complications can occur in the form of adhesions or ovarian cysts, both of which can be resolved with surgery.
Endometriosis is diagnosed by way of a laparoscopy, a procedure which is performed under general anaesthetic. This involves passing a viewing tube into the body, usually through the naval, in order for the gynaecologist to see where the tissue might be present. The specialist may then take a biopsy for further testing.
Sadly there is no cure for endometriosis, but treatment may help to ease the symptoms and, as mentioned, improve fertility.
What type of treatment the specialist recommends will depend on your age, primary symptom, and your desire to have children or not. In roughly a third of cases, the condition gets better without the need for treatment, but it is important to keep a close eye on the symptoms in case they worsen.
Paracetamol, codeine and non-steroidal anti-inflammatories such as ibuprofen may be advised for the pain, while hormone treatments that limit the production of oestrogen, which encourages the growth of endometriosis, may also help to ease the symptoms.
Laparoscopic surgery may be necessary to remove or destroy the endometriosis tissue, and this can help to improve symptoms. According to the NHS, eating a healthy, balanced diet can also benefit sufferers, as it helps to increase energy levels, and regulate bowel movements and sleep patterns.
For those that are having trouble coping with their level of pain, or the problems associated with the condition, the charity Endometriosis UK can offer support and advice via their website or helpline, and can also provide information about local support groups in your area.
If you are concerned that you may be displaying one or some of the symptoms, do visit your GP to discuss your options.