• To determine what dose of Finasteride, when combined with Oral TU, will yield an average serum testosterone over 24 hours in the eugonadal range while at the same time maintaining serum DHT concentrations within the normal range. [ Time Frame: 24-hours ] [ Designated as safety issue: Yes ]
  

We will be using three drugs: The first, acyline, temporarily turns off the body's production of testosterone for about two weeks. Subjects will receive acyline as shots three times over a six-week drug administration period. During the time when the body's production of testosterone is turned off, we will give testosterone either by itself or with a medication called finasteride by mouth twice daily for one week to see how much is absorbed and present in the bloodstream after administration. Subjects will go through three one-week study drug exposure periods. During two of the three one-week study drug administration periods subjects will also take a second medication, finasteride, by mouth twice daily. On the last day of each one-week drug administration period, subjects will be admitted to the University of Washington General Clinical Research Center overnight for monitoring of your blood testosterone levels. There will be 3 overnight visits for this study. This study will allow us to determine the absorption of testosterone taken by mouth, and the relative impact of two different doses of oral finasteride on testosterone absorption.