This research proposal aims at investigating the role of Wnt signaling molecules, RANKL and OPG in the regulation of bone metabolism and trabecular and cortical bone charachteristics during different stages of life in men, i.e. during puberty, at adult age and during senescence. In addition, possible determinants of the Wnt OPG/RANKL/RANK systerms will be explored, focusing on sex steroïd status.