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作者：John F Aloia, Sonia A Talwar, Simcha Pollack, Martin Feuerman and James K Yeh, 作者单位：1 From the Bone Mineral Research Center, Winthrop University Hospital, Mineola, NY.2 Supported by grant no. RO1 AG15325 from the National Institute of Aging, National Institutes of Health.3 Address reprint requests and correspondence to JF Aloia, Winthrop University Hospital, 222 Station Plaza North
【摘要】
Background: Optimal vitamin D status for the prevention of osteoporosis has been inferred from examinations of the serum 25-hydroxyvitamin D concentration below which there is an increase in serum parathyroid hormone (PTH).
Objective: 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.
Design: 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.
Results: 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.
Conclusion: Although a threshold for 25(OH)D can be identified, we suggest that it should not be used to recommend optimal vitamin D status.
【关键词】 african americans vitamin parathyroid hormone pth osteoporosis calcium intake secondary hyperparathyroidism
INTRODUCTION
The purpose of calcium intake in midlife is to replace the calcium lost through excretion so that the loss does not have to be offset from the skeleton (1). There is general agreement that an intake of 1000C1500 mg Ca/d should be recommended for white postmenopausal women (2, 3). There is insufficient information to make a definitive recommendation for other ethnic groups.