Contraceptive and therapeutic effects of the levonorgestrel intrauterine system: An overview

The levonorgestrel intrauterine system (LNG IUS), a steroid-releasing intrauterine system, is a T-shaped device that releases levonorgestrel directly into the uterine cavity at an initial rate of 20 μg per day. The contraceptive and therapeutic benefits of the LNG IUS stem primarily from its local effects. The local hormone delivery causes high levonorgestrel levels in the endometrial tissue but low levels in the systemic circulation. This leads to strong endometrial suppression and, in many cases, a dramatic reduction in menstrual blood loss. The high contraceptive efficacy is well documented through extensive international clinical research. This review article provides an overview of the LNG IUS and addresses the following topics: mechanisms of action, contraceptive efficacy, changes in bleeding patterns, principal safety issues, potential noncontraceptive benefits, and implications for women's reproductive health.