正常女性与年龄相关的骨转换生化指标和骨密度的关系

目的　探讨女性人群骨转换生化指标 :血清骨特异性碱性磷酸酶 (sBAP)、血清骨钙素(sOC)和尿Ⅰ型胶原氨基末端肽 (uNTX)随年龄变化及其与骨密度 (BMD)之间的关系。方法　用ELISA测定sBAP、sOC和uNTX ,用DXA仪测定腰椎 1～ 4前后位 (AP)、股骨颈 (FN)的BMD。结果( 1)sBAP、sOC和uNTX与年龄呈正相关 ,3个骨生化指标随年龄的变化均以三次回归模型的拟合程度最好 ,拟合曲线的决定系数 (R2 )为 0 181～ 0 381(P <0 0 0 1)。 ( 2 )按每 10岁年龄段分组发现 :这3个生化指标在 30～ 39岁年龄段最低 ,随后随年龄的增长而升高 ;5 0～ 5 9岁段达最高值。 ( 3)按是否绝经分组结果表明 :绝经后妇女sBAP、sOC和uNTX水平均较绝经前妇女高 (P <0 0 0 1) ,而绝经后妇女的AP、FN部位的BMD都低于绝经前妇女 (P <0 0 0 1)。( 4 )sBAP、sOC与uNTX呈正相关 (P<0 0 0 1) ,sBAP、sOC和uNTX与AP、FN部位的BMD呈负相关 (P <0 0 0 1)。结论　sBAP、sOC和uNTX是反映女性随年龄及绝经变化的骨转换的敏感和较特异的指标 ,能较好地预测BMD ,妇女BMD降低与骨的代谢转换率升高有关。

The relationships between biomarkers of age-related changes in bone turnover and bone mineral density in healthy Chinese women

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.