In normal men, the male hormone testosterone affects a number of things in the body including muscle function and sexual function. An enzyme in the body called 5-alpha reductase converts testosterone into another form called dihydrotestosterone (DHT) which has slightly different effects. The purpose of this study is to find out how different amounts of the two different forms of testosterone affect muscle function and sexual function in healthy young men like you. This will be done by giving the men participating in the study different combinations of hormone-related medication for 20 weeks and making measurements before, during and after the medications to look for changes in lean body tissue, muscle size, muscle strength and leg power, as well as sexual function and sexual activity in all participants.