In addition to birth control, the hormonal IUD is used for prevention and treatment of:

Heavy menstrual periods
Endometriosis and chronic pelvic pain
Adenomyosis and dysmenorrhea
Anemia
Endometrial hyperplasia (especially in pre-menopausal women who wish to maintain fertility in the treatment of endometrial hyperplasia)
In some cases, use of a hormonal IUD may prevent a need for a hysterectomy.Advantages:

Considered one of the most effective forms of reversible birth control
Can be used while breastfeeding (see also nursing mothers)
No preparations needed before sex, though routine checking of the device strings by patient and physician is advised to ensure proper placement remains intact
90% of users who wish to become pregnant do so within 24 months of removal. May experience lighter periods (some women stop having periods completely, see also amenorrhea)
Effective for up to three to seven years (depending on the IUD)Disadvantages:

Irregular periods and spotting between periods often occurs after insertion This usually improves after three to six months. Moderate to severe discomfort may be experienced during insertion procedure, including uterine cramping and back pain. Other potential adverse effects and risks

Effectiveness
After insertion, Mirena is effective at preventing pregnancy for up to seven years. Kyleena is approved for five years and Skyla is approved for three years.The hormonal IUD is a long-acting reversible contraceptive, and is considered one of the most effective forms of birth control. The first year failure rate for the hormonal IUD is 0.1-0.2% and the five-year failure rate is 0.7-0.9%. These rates are comparable to tubal sterilization, but unlike sterilization the effects of the hormonal IUD are reversible.
No longer-term studies have been performed to assess the long-term effects on infants of levonorgestrel in breast milk. There are conflicting recommendations about use of Mirena while breastfeeding. The U.S. CDC does not recommend any hormonal method as a first choice of contraceptive for nursing mothers, although progestin-only methods, such as Mirena, may be used with close follow-up or when the benefits outweigh the risks. The World Health Organization recommends against immediate postpartum insertion, citing increased expulsion rates. It also reports concerns about potential effects on the infants liver and brain development in the first six weeks postpartum. However, it recommends offering Mirena as a contraceptive option beginning at six weeks postpartum even to nursing women. Planned Parenthood offers Mirena as a contraceptive option for breastfeeding women beginning at four weeks postpartum. Contraindications
A hormonal IUD should not be used by women who:

Are, or think they may be, pregnant
Have abnormal vaginal bleeding that has not been explained (controversial)
Have untreated cervical or uterine cancer
Have, or may have, breast cancer
Have abnormalities of the cervix or uterus (controversial)
Have had pelvic inflammatory disease within the past three months
Have had an STI such as chlamydia or gonorrhea within the past three months
Have liver disease or tumor
Have an allergy to levonorgestrel or any of the inactive ingredients included in the deviceInsertion of an IUD is acceptable after a dilation and evacuation (D&E) abortion (second-trimester abortion), but may be associated with a higher expulsion rate.