Predictors of bone mineral density in aging healthy men varies by skeletal site

Factors contributing to the pathogenesis of osteoporosis in women are well defined. However, changes in bone mineral metabolism in aging men and the role of various factors in the pathogenesis of age-related bone loss in men are less well understood. To further clarify these changes, serum and urine biochemical parameters, and lumbar spine, hip, and total body bone mineral density (BMD) were evaluated in a small sample of 45 healthy men aged 20-80 years, and multiple regression models were developed to predict age-related bone loss. Serum calcium, phosphate, albumin, creatinine clearance, osteocalcin, C-terminal propeptide of type I procollagen, log-free androgen index, dehydroepiandrosterone sulfate (DHEA-S), and androstenedione decreased with age, and serum sex hormone binding globulin and urine total and free pyridinoline increased with age. Femoral neck BMD decreased with age, but remained stable at the other sites measured. Multiple regression analysis indicated that serum phosphate, DHEA-S, and intact parathyroid hormone (PTH) predicted lumbar spine BMD. Age, serum phosphate, and PTH predicted femoral neck BMD. Urine-free deoxypyridinoline alone predicted femoral greater trochanter BMD. Weight, serum creatinine, and urine-free deoxypyridinoline predicted total body BMD. We conclude that predictor variables of bone density vary by skeletal site in healthy men. Alterations in adrenal androgens, phosphate, and PTH may be important in the pathogenesis of bone loss with aging in men.