Testosterone Levels Associated with Sexual Function in Older Men

Testosterone Levels Associated with Sexual Function in Older Men

The Study

Glenn R. Cunningham, MD, of the division of diabetes, endocrinology and metabolism at Baylor College of Medicine, and colleagues evaluated 788 men aged at least 65 years participating in the Testosterone Trials (TTrials) who had low testosterone levels to determine whether sexual function, vitality and physical function are associated with baseline serum total testosterone, free testosterone, estradiol and sex hormone-binding globulin levels. The TTrials included the Sexual Function Trial (n=470), Vitality Trial (n=474) and the Physical Function Trial (n=390); participants could be part of more than one trial.

Participants from all three trials had similar mean BMI, total testosterone, free testosterone, estradiol and SHBG levels.

Participants in the Physical Function Trial had slower mean gait speed compared with the other two trials. Total testosterone was associated with significant increases in mean sexual desire (P=.03), erectile function (P=.004) and sexual activity (P=.02). Similarly, free testosterone was associated with significant increases in sexual desire (P=.02), erectile function (P=.005) and sexual activity (P=.01).

There was a significant association between total testosterone and erectile function (P=.005) and sexual activity (P=.03) and a marginal association between total testosterone and sexual desire (P=.055).

“We conclude that baseline [free testosterone] and [total testosterone], but not [estradiol] or SHBG, are consistently and independently associated with measures of sexual desire, erectile dysfunction and sexual activity in older men with low testosterone levels and symptoms of sexual dysfunction,” the researchers wrote. “These findings suggest that the circulating [free testosterone] and [total testosterone] levels contribute more than [estradiol] or SHBG to the variation in some measures of sexual dysfunction in older men with low [total testosterone]. In contrast, we did not find an association between baseline [free testosterone], [total testosterone], [estradiol] or SHBG and measures of vitality or physical function in the participants who qualified for those trials.”