Relation between Serum Testosterone, Serum Estradiol, Sex Hormone-Binding Globulin, and Geometrical Measures of Adult Male Proximal Femur Strength

Abstract

Although previous studies have indicated associations between circulating testosterone (T) or estradiol (E2) concentrations and bone mineral density, the relationship between gonadal steroids and skeletal geometry is not well defined. Our objective was to uncover the relation between circulating T or E2 and proximal femur geometry in a diverse sample of men. We used data on 808 men enrolled in the Boston Area Community Health/Bone Study. Serum concentrations of total and calculated free T and E2 were obtained via early-morning blood sampling. The geometry of the proximal femur at three sites (the narrow neck, intertrochanter, and shaft) was obtained using the Hip Structural Analysis technology. Analyses adjusted for subjects' age, height, total body lean mass and fat mass, and level of physical activity were performed. In-home interviews accompanied by subject visits to the General Clinical Research Center at Boston University School of Medicine were performed. A randomly selected cohort of men living in Boston, MA (ages 30-79 yr) was included in the study. These were not applicable. Bone mineral density and bone outer diameter, cross-sectional area (measuring bone material), and section modulus (an index of bending strength) were calculated. In age-adjusted models, E2 was positively associated with hip strength parameters, whereas T was not. Adjustment for age and other parameters resulted in substantial reductions in, but not complete elimination of, associations between E2 and hip strength parameters. Circulating E2 is strongly associated with proximal femur strength, an association that is partially mediated by body composition.