High bone turnover is associated with low bone mass in both pre- and postmenopausal women

In 979 healthy women, aged 30-75 years, bone mass was measured by DXA in the lumbar spine and proximal femur, and by SXA in the distal forearm. Bone turnover was assessed by urinary CrossLaps (CrossLaps ELISA), a new assay which measures type I collagen degradation products in urine and by osteocalcin (two-site N-Mid hOsteocalcin ELISA), a new assay which measures the N-terminal-mid fragment (1-43) as well as the intact (1-49) osteocalcin (OCN-Mid) in serum. For comparison data on urinary hydroxyproline (fU Hpr/Cr) and serum, total alkaline phosphatase were included (AP). In premenopausal women below 50 years of age, the concentrations of the biochemical markers were stable with age. At menopause CrossLaps and OCN-Mid increased abruptly to a level 60% and 35% above the premenopausal mean values (p < 0.001). Premenopausal women in the highest quartiles, stratified according to the concentration of CrossLaps and OCN-Mid corrected for height and weight, had 6%-11% lower bone mass in all regions (p < 0.01) as compared to women in the lowest quartiles. CrossLaps and OCN-Mid corrected for height and weight correlated with bone mass in the spine and proximal femur, r = -0.13 to r = -0.28, p < 0.05. In postmenopausal women, the difference in bone mass between the highest and lowest quartiles was 8%-14% (p < 0.001). CrossLaps and OCN-Mid correlated with bone mass measured in all regions, r = -0.14 to r = -0.32, p < 0.05. The correlation between bone mass and AP and Fu Hpr/Cr was lower; r = -0.06 to r = -0.20 for premenopausal women, NS to p < 0.01, and r = -0.01 to r = -0.23, NS to p < 0.001 for postmenopausal women. In conclusion, the present data indicate that high bone turnover is associated with a significantly lower bone mass in not only postmenopausal, but interestingly also in premenopausal women. In consistence with previous results, we found that bone turnover increased perimenopausally and in the early menopause.