Sexual function does not change when serum testosterone levels are pharmacologically varied within the normal male range

Abstract

Objective: To examine the relationship between serum T levels and sexual function when T levels are varied in the normal male range by pharmacological means. Two groups of healthy men were treated with a depot form of GnRH agonist leuprolide acetate (Lupron depot; TAP Pharmaceuticals, Chicago, IL) on days 1 and 31 to suppress endogenous T production and either 4 (n = 6) or 8 (n = 5) mg/d T replacement by a sustained release, long-acting T microcapsule formulation on day 1. Outcome Measures: Sexual function was evaluated by daily logs of sexual activity and electroencephalogram-coupled nocturnal penile tumescence recording before and after 9 weeks of treatment. Results: Serum T levels in 4 and 8 mg/d groups were at low and high ends of the normal male range, respectively (10.5 ± 1.7 versus 26.5 ± 3.4 nmol/L). The number and duration of rapid eye movement (REM) periods, latency to REM sleep, erections/REM period, magnitude, and duration of tumescence were not significantly different between the 4 and 8 mg groups. Sexual logs also did not show significant differences in overall scores or in subcategories of intensity of sexual feelings (libido) and sexual activity between the two doses. Conclusions: These data indicate that erectile function and sexual activity and feelings are restored by relatively low T levels. These data may help explain why some partially hypogonadal men continue to have normal sexual function and the absence of good correlation between serum T levels in the normal range and sexual function.