- Autoimmune diseases — disorders in which the immune system attacks the body's own tissues.
- Chronic fatigue syndrome — a strong feeling of fatigue that lasts for at least six months without letting up.
- Fibromyalgia — a recurrent pain in the muscles, tendons, and ligaments.
- Endocrine diseases — disorders of the glandular tissue
- Atopic diseases — such as allergies or asthma
The researchers found that women with endometriosis were at greater risk than were other women for such autoimmune diseases as systemic lupus erythematosus, Sjögren’s Syndrome, rheumatoid arthritis, and multiple sclerosis. The women in the study were over a hundred times more likely to experience chronic fatigue syndrome than the general population of U.S. women. The women with endometriosis were more than twice as likely as other women to experience fibromyalgia. In addition, 20 percent had more than one other disease, and up to 31 percent of those with more than one disease had also been diagnosed with either fibromyalgia or chronic fatigue syndrome. Hypothyroidism — an underactive thyroid gland — was seven times more common in the endometriosis patients. In many cases, hypothyroidism may also be an autoimmune disorder, resulting from an immune system attack on the thyroid gland. The researchers also found that the rates of allergies and asthma were higher among women with endometriosis than among women in the U.S. population, and higher still if they had other diseases. The researchers found that 61 percent of the women with endometriosis reported allergies (as compared to 18 percent of the general female population) and 12 percent had asthma (as compared to 5 percent). If a woman had endometriosis and an endocrine disease, the percent with allergies rose to 72 percent, and if a woman had endometriosis plus fibromyalgia or chronic fatigue syndrome, the rate for allergies rose to 88 percent. Two-thirds of the women reported that relatives also had diagnosed or suspected endometriosis, suggesting a familial basis for the condition.