 - Biochemical markers: selected biochemical markers of bone metabolism were measured at T0, T3, T6 and T12 or at the time of premature withdrawal in case of drop-out using commercially available kits. Bone formation was assessed by serum bone-specific alkaline phosphatase BAP and osteocalcin OC levels using commercially available kits. Bone resorption was assessed in serum by the C-terminal telopeptide of type I collagen degradation Crosslaps R and urinary N-terminal telopeptide of type I collagen degradation Osteomark R. 