It’s tempting to think that bringing testosterone back to “healthy youthful levels” will mean that a return of overall youth and fitness will follow. But it probably doesn’t work that way UNLESS the person in question actually IS youthful with a medical problem that has resulted in abnormally low testosterone. For the older man (say 50+), youthful levels may be neither normal nor healthy in a body that is no longer young in every other respect. The point here is, tread with caution. There could be serious, unforeseen downsides–just as there have been with HRT for women.