HIGH BONE TURNOVER IS ASSOCIATED WITH LOW BONE MASS AND SPINAL FRACTURE IN POSTMENOPAUSAL WOMEN

A group of 366 healthy, white postmenopausal women, aged 50-81 years, mean age 66 years, were selected from the screened population of Scand inavians who were part of a multicenter study of the efficacy of tilud ronate, a new bisphosphonate, in established postmenopausal osteoporos is, Eighty-eight women had a lumbar spine bone mineral density (BMD) a bove 0.860 g/cm(2), and 278 women had a BMD below 0.860 g/cm2. Spinal fracture was diagnosed from lateral spine X-ray studies and defined as at least 20% height reduction (wedge, compression, or endplate fractu re) in at least one vertebra (T4-L4), Bone resorption was assessed by measurement of the urinary excretion of type I collagen degradation pr oducts by the CrossLapsTM enzyme-linked immunoassay (ELISA). Bone form ation was assessed by ELISA measurement of the N-terminal-midfragment as well as the intact serum osteocalcin (OCN-MID), thus omitting the i nfluence of the instability of osteocalcin caused by the labile 6 amin o acid C-terminal sequence. The women were divided into groups with hi gh or low bone turnover according to the concentrations of urinary Cro ssLapsTM or OCN-MID. Women in the quartiles with the highest concentra tions of CrossLaps [519 +/- 119 mu g/mmol (SD)] or OCN-MID [44.6 +/- 7 .5 ng/ml (SD)] had 10-16% lower spinal BMD compared with women in the lowest quartiles (CrossLaps 170 +/- 48 mu g/mmol (SD), and OCN-MID [22 .1 +/- 3.0 ng/ml (SD)] (P < 0.0004). The prevalences of spinal fractur e were 25 to 29% in the lowest quartiles, whereas the prevalences in t he highest quartiles were almost double-53-54% (P < 0.006). If the wom en were subgrouped according to spinal BMD and prevalence of spinal fr acture, corresponding results were found. Women with a BMD less than 0 .860 g/cm(2), without or with spinal fracture (n = 136 and n = 142), h ad 36-43% higher concentration of CrossLaps (P = 0.0001) and 11-15% hi gher concentration of OCN-MID (P < 0.02), as compared with women with a BMD above 0.860 g/cm(2) and no spinal fracture (n = 84). In conclusi on, the results indicate a strong association among high bone turnover , low bone mass, and prevalence of spinal fracture, which supports the theory that high bone turnover is a risk factor for spinal fracture a nd osteoporosis.