Inclusion Criteria:  Pre-menopausal female subjects, between 18 and 49 years of age, inclusive, at the time of signing informed consent. Subject must have a clinical diagnosis of endometriosis (laparoscopy or laparotomy) as documented by medical records within 10 years before screening. Subject must have a Composite Pelvic Signs and Symptoms Score total score of ≥ 6 with a score of at least 2 for DYS and at least 2 for NMPP at screening. Subject agrees not to participate in another interventional study while participating in the present study.  Exclusion Criteria:  Subject is pregnant or breastfeeding or is planning a pregnancy during the study period. Subject has chronic pelvic pain that is not caused by endometriosis or has any other chronic pain syndrome or other chronic therapy, or that would interfere with the assessment of endometriosis-related pain Subject has clinically significant gynecologic condition other than endometriosis Subject has previous history of a severe, life-threatening or other significant sensitivity to any opioids or non-steroidal anti inflammatory drugs (NSAIDS) or any contraindication to their use such as gastrointestinal ulcer or bleeding Subject has history of hysterectomy and/or bilateral oophorectomy Subjects with past or present pituitary tumor growth Subjects has a history of osteoporosis or other metabolic bone disease