Bone sialoprotein is a specific biochemical marker of bone metabolism in postmenopausal women:: A randomized 1-year study

Accelerated bone remodeling after the menopause is associated with increased bone loss that can be abolished using hormone replacement therapy (HRT). Biochemical markers of bone metabolism are known to correlate closely with changes in bone histomorphometry and osteodensitometry. Bone sialoprotein (BSP), a major constituent of bone matrix, is almost exclusively found in mineralized tissues and therefore considered a potential marker of bone metabolism. In 82 postmenopausal women, randomly allocated to either low-dose sequential HRT or no HRT, serum BSP was measured and compared with established specific biochemical markers of bone resorption [urinary deoxypyridinoline (DPD), pyridinoline (PYD) and amino-terminal telopeptide (NTx)] and markers of bone formation [serum osteocalcin (Oc) and bone-specific alkaline phosphatase (bALP)]. Longitudinal analysis showed a marked response of BSP levels following commencement of HRT, resulting in a 52% reduction after 12 months compared with initial values. The changes of BSP levels over time were at least as strong as in conventional markers of bone formation and resorption and paralleled their changes. A moderate to close correlation was found between BSP and both markers of bone resorption (r = 0.57 for NTx; r = 0.38 for DPD) and formation (r = 0.55 for Oc; r = 0.39 for bALP; p<0.0001, respectively). Our data demonstrate a cause and effect relationship between commencement of HRT and a change in serum BSP. In conclusion, serum BSP circumvents some of the limitations of urinary measurements and appears valuable for the quantitative monitoring of the skeletal response to HRT in healthy postmenopausal women.