Are femara (letrozole) and norethindrone used for stage 4 endometriosis?

Yes: Norethindrone acetate has been used for may years to help endometriosis pain. Femara (letrozole) has recently been tried with some success but there is much less data to go by. Both may be effective but may not work in every woman. Treatment must be highly individualized.

Not very successfull: No medical treatment has ever been shown to be effective in treating stage IV endo. This stage means that there is deeply invasive endo usually between the rectum and vagina or cervix. Endo nodules are by definition deeper than 5mm, and the hormones can't penetrate well and they don't respond. You need a surgeon very experienced in complex procedures to remove the endo.