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 increase d 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 mi neralized tissues and therefore considered a potential marker of bone metab olism. In 82 postmenopausal women, randomly allocated to either low-dose se quential HRT or no HRT, serum BSP was measured and compared with establishe d specific biochemical markers of bone resorption [urinary deoxypyridinolin e (DPD), pyridinoline (PYD) and amino-terminal telopeptide (NTx)] and marke rs of bone formation [serum osteocalcin (Oc) and bone-specific alkaline pho sphatase (bALP)]. Longitudinal analysis showed a marked response of BSP lev els following commencement of HRT, resulting in a 52% reduction after 12 mo nths compared with initial values. The changes of BSP levels over time were at least as strong as in conventional markers of bone formation and resorp tion and paralleled their changes. A moderate to close correlation was foun d 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, re spectively). Our data demonstrate a cause and effect relationship between c ommencement of HRT and a change in serum BSP. In conclusion, serum BSP circ umvents some of the limitations of urinary measurements and appears valuabl e for the quantitative monitoring of the skeletal response to HRT in health y postmenopausal women.