Endometriosis and the estrogen threshold theory. Relation to surgical and medical treatment.

Estrogen-dependent diseases often regress when estrogen production is reduced. Endometriosis is an estrogen-responsive disease, and the pelvic pain associated with it improves when estrogen production is reduced with bilateral oophorectomy or chronic gonadotropin releasing hormone (GnRH) agonist treatment. Unfortunately, reduction of estrogen production is associated with adverse side effects, such as vasomotor symptoms and bone loss. In women with endometriosis and pelvic pain, the combination of bilateral oophorectomy plus postoperative low-dose estrogen treatment produces sustained improvement in pain symptoms and reduces the hypoestrogenic side effects associated with bilateral oophorectomy. In a parallel manner, chronic GnRH agonist treatment plus low-dose steroid therapy (estrogen plus progestin or progestin only) is effective in the treatment of pelvic pain caused by endometriosis and reduces the hypoestrogenic effects associated with hypoestrogenism caused by the GnRH agonist. Since chronic GnRH agonist treatment is reversible and avoids surgery, it may become an important alternative to bilateral oophorectomy for the treatment of endometriosis.