In a phase 2 , multicenter , international , randomized , placebo-controlled , parallel-group , eight-group study , we evaluated the efficacy and safety of romosozumab over a 12-month period in 419 postmenopausal women , 55 to 85 years of age , who had low bone mineral density ( a T score of -2.0 or less at the lumbar spine , total hip , or femoral neck and -3.5 or more at each of the three sites ) .