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.