The purpose of this study is to assess how effective and safe denosumab is in a population of males with low bone mass at risk of fracture. The primary clinical hypothesis is that in men with low bone mineral density, the mean percent change in lumbar spine bone mineral density at 12 months in subjects receiving denosumab will be greater than in subjects receiving placebo. Denosumab is a fully human monoclonal antibody with a high affinity for Receptor Activator of Nuclear Factor (RANK) Ligand that can bind and neutralize the activity of human RANK Ligand similar to the action of endogenous osteoprotegerin.