The use of testosterone in hypogonadic men, known as testosterone replacement therapy, has become of increasing interest to both the medical and other communities over the past decade. Even though the knowledge of the potential benefits and risks of male testosterone replacement therapy has increased dramatically, there is still much that needs to be determined. Data concerning clinical effects of such replacement have accumulated and yet there has not been any controlled trial of this therapy for type 2 diabetes, insulin resistance and obesity. The purpose of this study is to find out the effect of testosterone replacement therapy by discussing limited number of clinical trials.