Profiles of endogenous circulating cortisol and bone mineral density in healthy elderly men

Exogenous glucocorticoids are known to increase the risk of osteoporosis. H owever, the contribution made by endogenous circulating cortisol concentrat ions to adult skeletal status remains unknown. We examined this issue in a sample of 34 healthy men, aged 61-72 yr. Venous blood samples were obtained under standard conditions every 20 min over a 24-h period. Measurements we re made of serum cortisol and cortisol-binding globulin. Bone mineral densi ty was measured at the lumbar spine and proximal femur using dual energy x- ray absorptiometry. Measurements were made at baseline and 4 yr later. Thes e was a weak negative association between integrated cortisol concentration and lumbar spine bone density (r = -0.37; P < 0.05); similar relationships (P < 0.05) existed at three of five proximal femoral sites. There were als o statistically significant positive associations between the trough cortis ol concentration and bone loss rate at the lumbar spine (r = 0.38; P < 0.05 ) femoral neck (r = 0.47; P < 0.001), and the trochanteric region (r = 0.41 ; P = 0.02) over the 4-yr follow-up period. The cross-sectional relationshi ps between cortisol concentration and bone density were removed by adjustme nt for body mass index, but the influence on bone loss rate remained signif icant after adjusting for adiposity, cigarette smoking, alcohol consumption dietary calcium intake, physical activity, and serum testosterone and estr adiol levels. These observations suggest that the endogenous cortisol profi le of healthy elderly men is a determinant of their bone mineral density an d their rate of involutional bone loss.