Biochemical markers as predictors of rates of bone loss after menopause

Biochemical markers of bone turnover may correlate with rates of bone loss In a group of postmenopausal women, but it is uncertain how useful they are in predicting rates of bone loss in the individual, The aim of this study was to determine the value of measurements of biochemical markers for the p rediction of rates of bone loss in the individual. We studied 60 postmenopa usal women (ages, 49-62 years), 43 of whom had gone through a natural menop ause 1-20 years previously and 17 of whom had undergone hysterectomy 3-22 y ears ago. Lumbar spine bone mineral density (BMD) was measured using dual-e nergy X-ray absorptiometry (DXA) over 2-4 years. Bone formation markers (bo ne-specific alkaline phosphatase [ibAP] and amino terminal of type I collag en [PINP] and osteocalcin [OC]) were measured in serum. Bone resorption mar kers (N-telopeptide of type 1 collagen [NTx] and immunoreactive free deoxyp yridinoline [iFDpd]) were measured in urine and corrected for creatinine (C r), Rates of bone loss were calculated as percent change per year, We found significant negative correlations (Spearman rank) between all measured bio chemical markers and rate of change in bone density with r values ranging f rom -0.35 to -0.52. When markers and rates of bone loss were divided into t ertiles, prediction of bone loss in an individual was poor (kappa < 0.2), T here was an exponential relationship between rate of bone loss and years si nce menopause (YSM) in the 33 women having a natural menopause (r(2) = 0.44 ; p = 0.008) indicating higher rates of loss in the early postmenopausal pe riod. Levels of NTx, iFDpd, and PINP also showed a significant negative cor relation with YSM. We conclude that there is a strong relationship between rates of spinal bone loss and levels of bone turnover markers. Although thi s is a small study, the results also suggest that using DXA measurements of the lumbar spine as the "gold standard," it is not possible to use biochem ical markers to predict rate of bone loss in the individual.