骨质疏松症是罹患于绝经后妇女和老年男性的常见疾病，骨质疏松性骨折是其最严重并发症。维生素D水平与骨密度和椎体骨折的发生是否存在因果关联一直存在争议且是近年来的热点，而孟德尔随机化分析是解决上述因果关系的可靠方法之一。本研究在我们前期已完成椎体骨折工作基础上纳入1200名上海市绝经后妇女，检测血清25-羟维生素D [25(OH)D]水平；利用胸腰椎侧位X线片和半定量读片法判断是否存在椎体骨折；采用双能X线吸收仪检测骨密度。提取每例受试者外周血基因组DNA用于单核苷酸多态性位点的基因分型。选取已证实对血清25(OH)D水平有影响的4个基因共10个位点进行分型。利用统计学处理方法和孟德尔随机化工具来阐明血清25(OH)D水平与骨密度、椎体骨折的确切关系。本研究可进一步明确维生素D与骨质疏松、骨健康的关系，为今后临床诊治及政策制定提供宝贵数据。

Osteoporosis is a common disease in postmenopausal women and elderly men. Osteoporotic fracture is the most serious complication of osteoporosis. The causal associations between vitamin D level and bone mineral density (BMD) and vertebral fracture has been a controversial issue in recent years and Mendelian randomization may be the way to solve it. In this study, 1200 postmenopausal females in Shanghai were enrolled. Serum 25-hydroxyvitamin D levels were measured; vertebral fracture was defined by lateral X-ray film and semi-quantitative method was adapted; bone mineral density was measured by dual-energy X-ray absorptiometry. Meanwhile, genomic DNA from peripheral blood was extracted for genotyping of single nucleotide polymorphisms (SNP) loci. SNP was used to select genes related to vitamin D metabolism. The exact relationship between serum 25(OH)D level and BMD in vertebral fractures was clarified using statistical methods and Mendelian random tools. This study may provide the relationship between vitamin D and bone health in osteoporosis and obtain valuable data for clinical diagnosis and treatment and policy formulation in the future.