478 participants were randomly assigned at a ratio of 2:1 to the following treatment groups:
1. Elagolix 300 mg twice daily (BID) plus estradiol 1.0 mg/norethindrone acetate 0.5 mg (E2/NETA) once daily (QD) for 48 months, followed by 12 months PTFU
2. Placebo for 12 months, followed by elagolix 300 mg BID plus E2/NETA QD for 36 months, followed by 12 months PTFU
This study was double-blinded during the first 12 months and open-label for the next 36 months. Participants entered up to 12 months of PTFU after completing treatment Month 48 (or at any time a participant prematurely discontinued treatment).