The side effects of testosterone replacement therapy in men with benign prostatic hyperplasia include the development of prostate cancer and cardiovascular disease.15,33,44 Studies also report an increase in the PSA level, which can induce prostatic hyperplasia and prostate cancer.45,46 In this study, we measured the serum PSA level in men treated with MR-10 and found no difference. The gene discussed is KLK3; the disease is prostate cancer.