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Endometriosis is the most common reproductive disease afflicting young women, often leading to debilitating chronic pelvic pain and impaired quality of life. Safe, effective, and convenient long-term treatments are lacking for adolescents and young adults. The levonorgestrel-containing IUD (LNG-IUD) represents an attractive long-term drug delivery system for the treatment of endometriosis during adolescence and young adulthood. However, while the LNG-IUD has an acceptable safety profile, it is not associated with a favorable bleeding profile and may not fully suppress endometriosis pain when used as monotherapy. Investigators hypothesize that the addition of NETA will improve bleeding patterns, maximize pain control, and improve continuation rates of the IUD when the two medications are used in combination. This proposed prospective trial provides the ideal context in which to investigate these clinical questions and advance research on the best treatments for endometriosis.

Endometriosis is a major source of morbidity for U.S. females, affecting ~49% of adolescents with chronic pelvic pain and 10% of all women of reproductive age. This percentage translates into approximately 176 million women worldwide who may suffer from endometriosis. Annual health care costs are estimated to be over $22 billion in the US alone. Over 50% of adults with endometriosis report onset of severe pelvic pain during their adolescence. Symptoms result in decreased quality of life, negative socioeconomic consequences, impaired reproductive potential, and diminished mental health. Endometriosis is a chronic disease that progresses over time in more than half of patients. Endometriosis has no cure. For adolescents in particular, this means that the impact of endometriosis and its symptoms can last for decades. Appropriate management involves not only prompt initiation of therapy, but also the maintenance of therapy for a protracted length of time.

Medical therapy for endometriosis typically includes oral progestins or contraceptive pills. Though often effective, these options are associated with systemic side-effects which may further affect compliance and preclude long-term use. Furthermore, the need for repeated or regular administration compromises compliance and therefore efficacy. The levonorgestrel-releasing intrauterine system (LNG-IUD) has been evaluated as a promising treatment for endometriosis in adult women. The LNG-IUD 52 mg (Mirena) delivers levonorgestrel (LNG) to the uterine cavity at a steady rate of 20 µg/day over 5 to 6 years. The LNG causes atrophy and pseudo decidualization of the uterine lining, along with apoptosis of endometrial glands and stroma. As the LNG-IUD requires no further patient action following insertion, patient compliance is excellent. While continuation of the device is generally very good in adults, unfavorable uterine bleeding patterns are the most frequent reason for early device removal, particularly within the first 6 months. Anecdotal clinical experience suggests that combining use of the LNG-IUD with low-dose oral progestin therapy may maximize effectiveness and continuation of the LNG-IUD device in adolescents.

The investigators will recruit 80 adolescents for participation in a double-blind, randomized trial of NETA (n=40) vs. placebo (control group, n=40) for adjunct treatment to the levonorgestrel-containing IUD for pelvic pain due to endometriosis. It is believed that a combination of the locally-acting LNG-IUD plus systemic NETA may be the optimal combination to effectively treat endometriosis pain, minimize side effects, provide contraception, and control bleeding for adolescents with endometriosis.

Inclusion Criteria:

• Female with surgically confirmed endometriosis
• Clinical decision to begin use of the LNG-IUD
• Age 13 to 24 years
• Current pelvic pain (score ≥ 3 on Visual Analog Scale) that has been present for at least 2 months prior to enrollment
• Willingness to comply with visit schedule and study protocol

Exclusion Criteria:

• Pre-menarche or post-menopause
• Previous gonadotropin-releasing agonist use
• Contraindications to an IUD (e.g., cavity-distorting uterine anomaly, acute pelvic inflammatory disease, <3 months from postpartum endometritis or septic abortion, local neoplasm, uterine bleeding of unknown etiology, breast cancer, untreated cervicitis or vaginitis or other lower genital tract infections)
• Active or historical venous thromboembolism, active or recent arterial thromboembolic disease
• Impaired liver function or liver disease
• Systemic lupus erythematosus
• Uncontrolled diabetes or uncontrolled hypertension (BPs >140s/90s)
• Hypersensitivity to any component of the NETA or LNG-IUS
• Concurrent use of moderate or strong CYP34a inducers or inhibitors (such as erythromycin, ketoconazole, phenobarbital, rifampin)
• Significant mental or chronic systemic illnesses that may impact pain assessment
• Breast feeding, giving birth within the last 6 months, pregnancy, or planning to become pregnant in the next 12 month