Long-Term Safety Study of Elagolix in Combination With Estradiol/Norethindrone Acetate for the Management of Heavy Menstrual Bleeding Associated With Uterine Fibroids in Premenopausal Women

Inclusion Criteria: * Participant is a premenopausal female at the time of Screening. * Participant has a diagnosis of uterine fibroids documented by a Pelvic Ultrasound \[Transabdominal ultrasound (TAU) or transvaginal ultrasound (TVU)\]. * Participant has Heavy Menstrual Bleeding (HMB) associated with uterine fibroids as evidenced by Menstrual Blood Loss (MBL) \> 80 mL during each of two screening menses as measured by the alkaline hematin method. * Participant has negative urine and/or serum pregnancy test during Washout (if applicable) and/or Screening and just prior to first dose. * Participant has an adequate endometrial biopsy performed during Screening, the results of which show no clinical significant endometrial pathology. Exclusion Criteria: * Participant has screening pelvic ultrasound or Saline Infusion Sonohysterography (SIS) results that show a clinically significant gynecological disorder. * Participant has history of osteoporosis or other metabolic bone disease. * Participant has clinically significant abnormalities in clinical chemistry, hematology, or urinalysis. * Participant has a history of major depression or post-traumatic stress disorder (PTSD) episode within 2 years of screening, OR a history of other major psychiatric disorder at any time (e.g., schizophrenia, bipolar disorder). * Participant is using any systemic corticosteroids for over 14 days within 3 months prior to Screening or is likely to require treatment with systemic corticosteroids during the course of the study. Over the counter and prescription topical, inhaled, intranasal or intra-articular injectable (for occasional use) corticosteroids are allowed.