Endometriosis is the outcome of endometrium (tissue of the uterine lining) growing in other areas of a woman's body. This can cause irregular bleeding and pain and may cause infertility.
Hormones from the ovaries stimulate endometrium growth every month in preparation for possible pregnancy. If the endometrium goes out of bounds into areas outside of the uterus, this is where the trouble begins. Pain and possible scarring can occur on the fallopian tubes and ovaries, and within the pelvis.
Since progestin is similar to progesterone, it also decreases estrogen production which in turn stops a woman from ovulating and having menstrual periods. Progestins block luteinizing hormone (LH) which helps stop ovulation.
Progestin is an effective hormone therapy, and is one of the oldest treatments for endometriosis. It is usually not tried until birth control pills or gonadotropin-releasing hormone agonist (GnRH-a) therapies have been attempted. These are preferred treatments since high-dose oral or injected progestin like Depo-Provera and Megestrol can have adverse side effects such as thinning of the bones.
High dose progestin can end menses and cause irregular spotting or light vaginal bleeding. It can cause tenderness of the breasts, edema (water retention) and weight gain. Depression and other mood changes can also result.
The progestin intrauterine device (IUD), on the other hand, poses less risk of these side effects because it provides a lower dose of progestin.
The progestin IUD is also not known to have any adverse effect on the bones or cause other negative effects. Progestin from the IUD affects only the uterus and cervix without affecting other areas of the body.
Progestin does not cure endometriosis but then no known treatment can do this.