Abstract: Methods for modulating one or more side effects of 5-?-reductase inhibitor therapy are provided, where the method includes administering a 5-?-reductase inhibitor and testosterone undecanoate. Also provided are methods of maintaining or restoring a DHT serum level in an individual undergoing 5-?-reductase inhibitor therapy, where the method includes administering testosterone undecanoate in addition to 5-?-reductase inhibitor. Further provided are methods of treating or preventing a DHT-related condition, such as benign prostate hyperplasia (BPH) or prostate cancer by administering a 5-?-reductase inhibitor and testosterone undecanoate.