Aloia John F, Talwar Sonia A, Pollack Simcha, Feuerman Martin, Yeh James K
Bone Mineral Research Center, Winthrop University Hospital, Mineola, NY 11501, USA.
Am J Clin Nutr. 2006 Sep;84(3):602-9. doi: 10.1093/ajcn/84.3.602.
Optimal vitamin D status for the prevention of osteoporosis has been inferred from examinations of the serum 25-hydroxyvitamin D [25(OH)D] concentration below which there is an increase in serum parathyroid hormone (PTH).
The objectives of the study were to ascertain whether a threshold for serum 25(OH)D exists below which serum PTH increases and whether persons with 25(OH)D above this threshold have lower rates of bone loss than do persons with 25(OH)D below the threshold.
The relation of serum 25(OH)D to serum PTH was analyzed in 208 African American women studied longitudinally for 3 y. These healthy women in midlife were randomly assigned to receive placebo or 800 IU vitamin D3/d; after 2 y, the vitamin D3 supplementation was increased to 2000 IU/d. Both groups received calcium supplements to ensure an adequate calcium intake. A systematic literature review found a wide range of threshold values in part due to varied calcium intake.
A Loess plot suggested a breakpoint between 40 and 50 nmol/L for serum 25(OH)D. A line-line model was fitted to the data, and it showed a spline knot at 44 nmol/L. A heuristic approach verified that PTH does not decline as rapidly when the serum concentration of 25(OH)D is >40 nmol/L as when it is <40 nmol/L. We found no significant difference in rates of bone loss between persons with 25(OH)D concentrations above and below 40 nmol/L.
Although a threshold for 25(OH)D can be identified, we suggest that it should not be used to recommend optimal vitamin D status.
预防骨质疏松症的最佳维生素D状态是通过检测血清25-羟基维生素D[25(OH)D]浓度推断出来的，低于该浓度时血清甲状旁腺激素(PTH)会升高。
本研究的目的是确定血清25(OH)D是否存在一个阈值，低于该阈值时血清PTH会升高，以及血清25(OH)D高于该阈值的人群的骨质流失率是否低于血清25(OH)D低于该阈值的人群。
对208名非裔美国女性进行了为期3年的纵向研究，分析血清25(OH)D与血清PTH之间的关系。这些处于中年的健康女性被随机分配接受安慰剂或800 IU/d的维生素D3；2年后，维生素D3补充量增加到2000 IU/d。两组均补充钙剂以确保充足的钙摄入量。一项系统的文献综述发现，由于钙摄入量不同，阈值范围很广。
一条局部加权回归散点图表明血清25(OH)D在40至50 nmol/L之间存在一个转折点。对数据拟合了一个线性模型，结果显示在44 nmol/L处有一个样条节点。一种启发式方法证实，当血清25(OH)D浓度>40 nmol/L时，PTH下降的速度不如<40 nmol/L时快。我们发现血清25(OH)D浓度高于和低于40 nmol/L的人群之间的骨质流失率没有显著差异。
虽然可以确定25(OH)D的一个阈值，但我们建议不应将其用于推荐最佳维生素D状态。
