Endometriosis can cause far more than painful periods. It drives chronic pelvic pain, infertility, digestive and urinary problems, fatigue, mood changes, and in rare cases, complications in organs as distant as the lungs. Because the condition takes between 4 and 11 years on average to diagnose, many people live with these effects for years without understanding their source.
The tissue involved behaves like the uterine lining but grows in places it shouldn’t: on the ovaries, fallopian tubes, bowel, bladder, and occasionally beyond the pelvis entirely. It responds to hormonal cycles, bleeding and triggering inflammation each month, which is why the damage compounds over time and affects so many different systems.
Chronic Pelvic Pain
Pain is the hallmark of endometriosis, and it goes well beyond typical menstrual cramps. Misplaced tissue bleeds cyclically, creating inflammation both at the lesion sites and throughout the pelvic cavity. The immune system releases inflammatory chemicals in response, which activate and sensitize nearby nerve fibers. Over time, those nerves become increasingly reactive, a process called peripheral sensitization, meaning stimuli that wouldn’t normally hurt begin to register as painful.
If this continues long enough, the central nervous system itself adapts. Pain signals get amplified in the spinal cord and brain, producing a chronic pain state that can persist even between periods or after lesions are treated. This is why some people with endometriosis experience constant pelvic pain rather than pain only during menstruation. Pain during sex, pain with bowel movements, and pain during urination are all common because the nerves serving the reproductive tract, colon, and bladder share overlapping pathways. Inflammation in one organ can trigger pain responses in the others, a phenomenon called cross-organ sensitization. This shared wiring also helps explain why endometriosis so often coexists with irritable bowel syndrome and overactive bladder syndrome.
Infertility
Roughly 30 to 50% of people evaluated for infertility turn out to have endometriosis. The condition undermines fertility through several routes at once.
Adhesions and scar tissue from chronic inflammation can physically distort the pelvis, pulling the ovaries, fallopian tubes, and uterus out of normal position. Thick bands of scar tissue can seal off the space behind the uterus or block the fallopian tubes, preventing sperm from reaching an egg or stopping a fertilized egg from traveling to the uterus.
Even when anatomy looks relatively normal, egg quality often suffers. Ovarian endometriosis consistently reduces both the number of eggs retrieved during fertility treatment and the proportion of those eggs that are mature. Under a microscope, eggs from affected ovaries frequently show structural problems: a hardened outer shell, disrupted internal scaffolding, and damaged energy-producing structures within the cell. Oxidative stress from the inflammatory environment injures the DNA inside the eggs themselves. All of this lowers the chances of successful fertilization and healthy embryo development, whether conception is attempted naturally or through assisted reproduction.
Digestive and Urinary Problems
Up to one-third of people with endometriosis have gastrointestinal involvement. The rectum and sigmoid colon are affected most often, but tissue can also grow on the small intestine, appendix, or bladder wall. Symptoms include bloating (sometimes called “endo belly”), cramping, nausea, diarrhea, constipation, and painful bowel movements, particularly around menstruation.
In its most aggressive form, deep infiltrating endometriosis invades through the wall of the bowel or bladder rather than sitting on the surface. Over time, repeated inflammation and scarring can form a stricture, a narrowing that partially or completely blocks the intestine. A full bowel obstruction causes escalating abdominal pain, vomiting, and visible abdominal distension. This is uncommon but serious, and it typically requires surgery. When endometriosis affects the bladder, it can cause urgency, frequency, and blood in the urine that worsens cyclically with the menstrual period.
Fatigue and Cognitive Effects
Persistent, heavy fatigue is one of the most commonly reported symptoms, yet it often gets overlooked in favor of pain. The root cause is largely inflammatory. As the immune system works to contain misplaced endometrial tissue, it releases cytokines, small signaling proteins that trigger widespread inflammation. These same molecules produce the kind of deep exhaustion people feel during a flu, except in endometriosis the process is ongoing.
Many people also report difficulty concentrating, memory lapses, and mental fogginess. Chronic pain and chronic inflammation both affect brain function, altering how the brain processes information. Combined with disrupted sleep from nighttime pain and the emotional toll of managing a long-term condition, the cognitive effects can be significant enough to interfere with work and daily life.
Anxiety and Depression
About 32% of people with endometriosis experience significant anxiety symptoms, making them roughly 2.8 times more likely to report anxiety than people without the condition. Depressive symptoms affect about 29%. The relationship between endometriosis and mental health runs in both directions: chronic pain and the unpredictability of symptoms fuel psychological distress, while the inflammatory chemicals involved in endometriosis can directly influence brain chemistry and mood regulation. Years of diagnostic delay, dismissed symptoms, and limited treatment options compound the emotional burden.
Autoimmune and Inflammatory Conditions
Endometriosis appears to shift the immune system in ways that increase vulnerability to other inflammatory and autoimmune diseases. Large survey data show that people with endometriosis develop lupus, Sjögren’s syndrome, rheumatoid arthritis, multiple sclerosis, and Hashimoto’s thyroiditis (underactive thyroid) at significantly higher rates than the general population. Fibromyalgia and chronic fatigue syndrome are also markedly more common.
Allergies and asthma follow a similar pattern. Asthma affects about 12.5% of people with endometriosis compared to 5.2% of the general female population, and that figure climbs even higher, to over 28%, among those who also have fibromyalgia or chronic fatigue syndrome. The exact mechanism connecting these conditions is still being worked out, but the shared thread appears to be a chronically dysregulated immune response that makes the body more reactive across multiple systems.
Ovarian Cancer Risk
Endometriosis raises the risk of ovarian cancer by roughly fourfold compared to people without the condition. The risk is concentrated in slow-growing subtypes known as type I ovarian cancers: clear cell carcinoma, endometrioid carcinoma, low-grade serous carcinoma, and mucinous carcinoma. For people with more severe endometriosis, the risk climbs to nearly 10 times that of the general population.
Important context: ovarian cancer is still relatively rare overall, so even a four- to tenfold increase translates to a small absolute risk for any individual. But the association is strong enough to be clinically meaningful, particularly for people with advanced disease or endometriomas (ovarian cysts caused by endometriosis) that persist over many years.
Thoracic Endometriosis
In rare cases, endometrial tissue reaches the chest cavity, most often the right side of the diaphragm or the lining around the lungs. The most dramatic result is catamenial pneumothorax, a collapsed lung that recurs within 72 hours of the start of a menstrual period. Symptoms include sudden chest pain and shortness of breath that come back month after month.
The tissue likely migrates upward from the pelvis through tiny natural openings or lymphatic channels in the diaphragm, which are more common on the right side. This explains why thoracic endometriosis is overwhelmingly right-sided. Once endometrial tissue is established in the chest, monthly hormonal cycling causes it to shed and bleed just as it does in the pelvis, irritating the lung lining and creating air leaks. Thoracic endometriosis is frequently misdiagnosed as a primary lung problem because clinicians may not connect chest symptoms to the menstrual cycle.