The levonorgestrel-releasing intrauterine system, Mirena IUS, is widely available in Europe and Asia, and it was approved for use in the United States in December 2000. It combines the best features of hormonal contraceptives and IUDs. It delivers the progestin levonorgestrel through an IUD and is effective for up to five years.
Mirena drastically reduces the excessive menstrual bleeding experienced by some women with uterine fibroids. But scientists do not know what molecular mechanism accounts for this improvement in symptoms. Council researchers and others are working to determine the underlying molecular cause of changes in the endometrium of women using Mirena.