Bone Geometry, Body Composition and Sex Hormones in Men

骨质疏松症的特点是骨质强度降低，导致骨折风险增加，在美国，1- 200万50岁或以上的男性患有骨质疏松症。骨密度降低对骨质疏松症和骨折风险的影响是众所周知的。然而，人们的注意力已经转向骨的几何形状，认为这是另一个可能影响骨折风险的骨骼特征。骨的几何形状是由骨内外表面组织的相对数量决定的。从生物力学的角度来看，骨骼强度在很大程度上取决于几何形状。老年男性中影响骨骼几何形状和骨骼强度的特征实际上是未知的。骨的生长和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，以及非机械因素，如内分泌作用。因此，我们假设老年男性髋部和脊柱的骨骼几何形状与腹部身体组成以及内源性睾酮和雌二醇水平有关。腹肌可能直接影响髋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或可能对骨骼施加内分泌影响。在老年男性中，睾酮似乎可以刺激骨骼生长，而雌二醇可能会抑制骨质流失。为了验证假设的关联，我们建议使用1800名65岁及以上的美国男性骨质疏松性骨折（MrOS）队列参与者的现有数据。在该队列中进行了定量计算机断层扫描（QCT）。髋部和脊柱的骨几何测量以及腹部的身体组成测量都来自这些扫描。对这些参与者也进行了睾酮和雌二醇的测定。我们将采用横断面设计量化髋部和脊柱骨骼几何形状与腹部身体组成、睾酮和雌二醇的关系。该计划将提供有关影响老年男性骨骼几何形状因素的新信息。

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.