Bone Geometry, Body Composition and Sex Hormones in Men

描述(申请人提供)：骨质疏松症的特征是骨强度降低，导致骨折风险增加。在美国，有100-200万50岁或以上的男性受到骨质疏松症的影响。骨密度降低对骨质疏松症和骨折风险的贡献是众所周知的。然而，人们的注意力已经转向骨骼几何，这是另一个可能影响骨折风险的骨骼特征。骨骼几何形状由内部和外部骨骼表面上的相对组织数量确定。从生物力学的角度来看，骨骼强度与几何形状密切相关。老年男性中影响骨骼几何形状和骨骼强度的特征几乎是未知的。骨生长和骨吸收是通过生物途径调节的，包括来自肌肉力量的机械负荷，以及内分泌效应等非机械因素。因此，我们假设老年男性髋部和脊柱中的骨几何形状将与腹部身体成分以及内源性睾酮和雌二醇水平有关。腹肌可能会直接影响臀部和脊柱的机械负荷。腹部脂肪组织可能影响整体负荷模式，也可能对骨骼产生内分泌影响。在老年男性中，睾丸激素似乎可以刺激骨骼生长，而雌激素可能会抑制骨丢失。为了检验假设的相关性，我们建议使用1,800名65岁及以上的美国男性的现有数据，他们是男性骨质疏松性骨折(MRO)队列的参与者。在这个队列中进行了定量计算机断层扫描(QCT)。髋部和脊柱的骨骼几何测量和腹部身体成分测量都是从这些扫描中得出的。还对这些参与者进行了睾酮和雌二醇的检测。我们将使用横断面设计来量化髋部和脊柱中的骨几何形状与腹部身体成分、睾酮和雌二醇的关系。这项拟议的项目将提供有关影响老年男性骨骼几何因素的新信息。

DESCRIPTION (provided applicant): Osteoporosis is characterized by reduced bone strength that results in an increased risk of fracture, in the US, 1-2 million men ages 50 years or older are affected by osteoporosis. The contribution of reduced bone density to osteoporosis and fracture risk is well known. However, attention has turned toward bone geometry as another skeletal feature that may influence fracture risk. Bone geometry is determined by the relative amounts of tissue on the inner and outer bone surfaces. From a biomechanical perspective, bone strength is vitally dependent on geometry. The characteristics among older men that influence bone geometry and bone strength are virtually unknown. Bone growth and resorption are regulated through biologic pathways that involve mechanical loading from muscle forces, as well as non-mechanical factors such as endocrine effects. Therefore, we hypothesize that bone geometry in the hip and spine among older men will be associated with abdominal body composition and with endogenous levels of testosterone and estradiol. Abdominal muscles may directly affect mechanical loads on the hip and spine. Abdominal adipose tissues may affect overall loading patterns or may exert endocrine influences on bone. In older men, testosterone appears to stimulate bone growth and estradioi may inhibit bone loss. To test the hypothesized associations, we propose to use existing data from 1,800 US men ages 65 years and older who are participants in the Osteoporotic Fractures in Men (MrOS) cohort. Quantitative computed tomography (QCT) scans have been performed in this cohort. Bone geometry measures in the hip and spine and abdominal body composition measures are derived from these scans. Assays for testosterone and estradiol have also been performed for these participants. We will quantify the associations of bone geometry in the hip and spine with abdominal body composition, testosterone and estradiol using a cross-sectional design. The proposed project will yield new information about factors that influence bone geometry among older men.