What are the causes of endometrial polyps/endometriosis?

Polysp are: The result of accelarated growth of the uterine lining (almost always benign) and not uncommon; endometriosis is different. Fragments of uterine lining go into abdominal cavity and implant on tubes, ovaries, abdominal wall, some women have altered immune system that (for whatever reason) isn't as adept at "removing" the tissue that is now in a foreign place; these implants are hormonally sensitive.