Endometriosis is the presence of endometrium at a site outside the uterine lining. It’s a hormone-dependent condition in women of childbearing age. Genetic factors and family history can increase the risk. Hormonal and immune system factors contribute to the development of endometriosis. One study states that menstrual blood flows backwards (Retrograde Menstruation) into the pelvic cavity, transporting endometrial tissue, which then implants and grows in an abnormal location, leading to symptoms like pain and inflammation.