Serum level of intact amino terminal propeptide of type I procollagen (PINP) and type 1 collagen cross-linked C-telopeptide (CTX) as well as DXA measurement at the spine, total hip and femoral neck BMD are evaluated at TPTD treatment initiation, at baseline of randomization to antiresorptive therapy as well as at 3 and 9 months during the combination treatment.Volumetric BMD values will be also determined.