Unfortunately, the cause of endometriosis is not completely understood, though a number of possible reasons for the disease have been addressed. Possible causes of endometriosis include:
Genetics. Endometriosis appears to run in families, which suggests a genetic component to the disease.
Menstrual Fluid Backup Endometriosis may be the result of a backup of menstrual fluids. If menstrual fluids back up through the fallopian tubes, it is possible that the tissue can take root outside of the uterus. This backup (retrograde menstruation or Sampson’s Hypothesis) is undoubtedly a cause of some endometriosis. Birth control pills have been known to work in treating this type of endometriosis.
Problems with Lymph and Blood Systems Endometriosis may be caused by a problem with your lymph or blood systems. These systems are responsible for distributing endometrial tissues around the body. This may explain why doctors are occasionally surprised to see rare cases of endometriosis in the lungs!
Spontaneous conversion of pelvic lining cells This theory (called coelomic metaplasia) is gaining more traction in recent years. Stem cells within the tissues which coat the pelvic organs may develop a mind of their own and begin to behave like and convert to endometrial cell types. These cells may be particularly aggressive since they can make their own estrogen (that is, they can fuel themselves), and they may resist treatment with progesterone-like hormones. Surgery is typically used to treat this type of aggressive endometriosis.