title: [The relationships between biomarkers of age-related changes in bone turnover and bone mineral density in healthy Chinese women].
abstract: OBJECTIVE
  To study the relationships of serum bone alkaline phosphatase (sBAP), serum osteocalcin (sOC) and the ratio of urine cross-linked N-telopeptide of collagen type I (uNTX)/creatine (Cr) with age and bone mineral density (BMD) in healthy women aged 20 - 80 years.
  
  
  METHODS
  sBAP, sOC and uNTX were measured using ELISA. BMD at lumbar spine 1 - 4 anteroposterior (AP) and at femoral neck (FN) was studied using DXA (QDR 4500A) in 668 healthy women. Correlations of bone biomarkers with age and BMD were fitted in entire female population by ten kinds of regression models.
  
  
  RESULTS
  (1) sBAP, sOC and uNTX were positively correlated with age (all P < 0.001). The cubic regression model was better fitted with age-related changes of bone biomarkers as compared with the other regression models and the coefficients of determination (R(2)) of fitting curve were 0.181 - 0.381 (P < 0.001). (2) When all subjects were stratified by 10-year age groups, the bone biomarker values during 30 - 39 years of age were the lowest, then they increased gradually to a highest level in the 50 - 59 years of age. (3) When subjects were stratified by menopause, levels of sBAP, sOC and uNTX in postmenopausal women with a low value of BMD at AP and FN were significantly higher than those in premenopausal women (all P < 0.001). (4) Positive correlation among sBAP, sOC and uNTX was found (all P < 0.001) and BMD values at AP and FN were negatively correlated with all the bone biomarkers (all P < 0.001).
  
  
  CONCLUSIONS
  sBAP, sOC and uNTX may be the sensitive and relatively specific markers to evaluate age- and menses-dependent changes of bone turnover, but they are negatively correlated with BMD, suggesting that individuals with increased bone biomarker levels are associated with a decreased BMD value.
authors.affiliation: Institute of Metabolism and Endocrinology, Xiangya Second Hospital, Central South University, Changsha 410011, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Liu
authors.forename: Er-Yuan
authors.initials: EY
authors.lastname: Liao
authors.forename: Xian-Ping
authors.initials: XP
authors.lastname: Wu
authors.forename: Hong
authors.initials: H
authors.lastname: Zhang
authors.forename: Xiang-Hang
authors.initials: XH
authors.lastname: Luo
authors.forename: Hui
authors.initials: H
authors.lastname: Xie
authors.forename: Xing-Zhi
authors.initials: XZ
authors.lastname: Cao
authors.forename: Shi-Ping
authors.initials: SP
authors.lastname: Liu
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000469:Alkaline Phosphatase / Q000097:blood*; D015519:Bone Density; D003094:Collagen / Q000652:urine*; D003401:Creatine / Q000652:urine; D005260:Female; D006801:Humans; D008875:Middle Aged; D015675:Osteocalcin / Q000097:blood*; D012044:Regression Analysis; D012680:Sensitivity and Specificity
chemical_list: C461299:urinary N-telopeptide of type I collagen, human; D015675:Osteocalcin; D003094:Collagen; D000469:Alkaline Phosphatase; D003401:Creatine