An Extension Study to Evaluate the Efficacy and Safety of Elagolix in Premenopausal Women With Heavy Menstrual Bleeding Associated With Uterine Fibroids

Inclusion Criteria: * Participant has completed the 6-Month Treatment Period of their respective Pivotal Study (either Study M12-815 or Study M12-817). * Participant did not meet removal criteria in bone mineral density (BMD) decrease in the spine, total hip and femoral neck at Month 6 of the Treatment Period of their respective Pivotal Study * Participant has negative urine and/or serum pregnancy test(s) results were consistently negative during the Treatment Period of their respective Pivotal Study and prior to first dose in this study. * Participant's endometrial biopsy from the Month 6 Visit of their respective Pivotal Study shows no clinically significant endometrial pathology. Exclusion Criteria: * Participant met criteria for removal from therapy in her respective Pivotal Study. * Participant is planning a pregnancy within the next 18 months. * Participant has current suicidal markers as noted at the Month 6 visit of her respective pivotal study. * Participant has any new medical conditions that may be unsuitable for participation. * Participant is using any systemic corticosteroids for over 14 days or is likely to require treatment with systemic corticosteroids during the course of the study. Over-the-counter and prescription topical, inhaled, intranasal or injectable (for occasional use) corticosteroids are allowed.