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Association between Seasonal Changes in Vitamin D and Bone Mineral Density

=Abstract= Objectives: Vitamin D deficiency, which causes secondary hyperparathyroidism, is considered to be a major contributor to osteoporosis. Because the serum 25-hydroxyvitamin D (25-OHD) level depend on sun exposure and, varies by season, the level of serum 25-OHD in each season at which vitamin D status can lead to changes in bone mineral density (BMD) is not known. Methods: A total of 2,878 women who underwent periodic health examinations at Ajou University Hospital were included in this study. We measured the serum 25-OHD concentrations using radioimmunoassay and BMDs using dual energy x-ray absorptiometry (DXA). The differences in serum 25-OHD levels among groups as a function of age, season, and BMD were tested by one-way ANOVA. Results: The serum 25-OHD level was not different based on age, but by season, with higher levels in the summer and autumn than in the winter and spring. However, the 25-OHD level did not have a significant relationship with BMD in any season. Conclusion: The serum 25-OHD level represents vitamin D status at the time of testing, which is not associated with long-term changes in BMD. When the 25-OHD levels are used to make clinical decisions related to the treatment of osteoporosis, careful interpretation is required. (J Korean Soc Menopause 2011;17:88-93)