If your level is only slightly low, nothing much happened
Men over 60 whose testosterone ran from 100 to 400 ng/dL took it for three years. Sexual desire, erections, overall sexual function and quality of life all matched placebo.
What the study found
Three years of testosterone moved nothing in barely-low men
This trial let in men over 60 with testosterone anywhere from 100 to 400 ng/dL, so many were not low by any guideline threshold. Over three years, sexual desire, erectile function, overall sexual function and quality of life all failed to separate from placebo, as did both artery measures.
The caveat · Built to study arteries, not sex
The trial was powered for artery thickening rather than for sexual outcomes, so the null on sex is a secondary result rather than a definitive one. Its authors say plainly that it should not be read as establishing cardiovascular safety. Haematocrit and prostate-specific antigen both rose more on testosterone.