What mattered was how far your level rose, not where it started
In 470 men over 65, ten of twelve sexual measures improved, and how much a man improved tracked the size of his rise. None of 27 starting traits predicted who would respond.
What the study found
No testosterone level marked the point where men responded
Ten of twelve sexual measures improved on testosterone in 470 men over 65. How much a man improved tracked how far his testosterone and estradiol rose, not where he started, and none of 27 baseline traits predicted response. Desire and activity followed the rise; erections did not.
The caveat · Only men with a willing partner
Men had to have a partner willing to attempt intercourse at least twice a month, which selects a particular and comparatively motivated group. Twelve outcomes were tested, so some of the ten significant ones may be the arithmetic of testing many things. And the missing threshold cuts both ways: it undercuts any single diagnostic cutoff, and it also means no reading identifies in advance who will benefit.