Levonorgestrel-releasing intrauterine system for the treatment of endometriosis: biological and clinical evidence.

Endometriosis-associated symptomatology can be safely and effectively treated with intrauterine-released progestin, which is associated with fewer adverse effects than other therapeutic options and may be used on a long-term basis. We have herein reviewed the current literature in relation to the biological and clinical rationale for the use of an intrauterine system releasing 20 microg/day of levonorgestrel for the treatment of pelvic pain symptoms associated with endometriosis. Levonorgestrel induces endometrial glandular atrophy and decidual transformation of the stroma, reduces endometrial cell proliferation and increases apoptotic activity. After the first year of use, a 70-90% reduction in menstrual blood loss is observed. The levonorgestrel-releasing intrauterine system has proven effective in relieving pelvic pain symptoms caused by peritoneal and rectovaginal endometriosis and in reducing the risk of recurrence of dysmenorrhea after conservative surgery. Thus, the intrauterine delivery of a potent progestin may constitute an innovative, effective, safe and convenient alternative for local delivery of a potent progestin in the long-term therapy of symptomatic endometriosis.