There is evidence pointing to a relationship between insulin and testosterone in men (testosterone is the male sex hormone that is produced in the testes). As men get older their testosterone levels decrease while their weight and insulin resistance tends to increase. The purpose of this research study is to learn more about the details of the relationship between insulin and testosterone. A clearer understanding of this relationship can have an important impact on public health due to the high rate of health problems associated with diabetes, obesity, and heart disease.