Effects of infused testosterone on mental performances and serum LH.

Abstract

Serial subtraction performances were measured before and after a 4-hr iv infusion of testosterone in 27 normal male subjects. Twenty-seven control subjects, individually matched with the testosterone infused subjects for initial serial subtraction performance ability, received control infusions. Testosterone was infused at a rate of 0.8 mg/hr. Plasma testosterone concentrations (PTC) and serum LH levels were measured at the beginning and end of the infusion in some subjects. The post-infusion task performances were poorer in both the testosterone and saline infused groups. However, the control group had a significantly greater decline in performance than the testosterone infused group (p<.05). The PTCs of the saline group declined 21%, probably reflecting the diurnal variation reported for PTC. Control subjects with the lowest post-infusion PTCs had significantly greater declines in performances than those with higher post-infusion PTCs (p<.02). In the subjects infused with testosterone the post-infusion PTCs increased by 44%. The testosterone infused subjects with the higher post-infusion PTCs had a greater deterioration in performances than the testosterone infused subjects with lower post-infusion PTCs (p <.002). The saline infusion produced no consistent change in LH, whereas the testosterone infusion suppressed LH levels in a significant number of subjects. Significantly less LH suppression occurred in the testosterone infused subjects with the higher post-infusion PTCs than in the testosterone infused subjects with lower post-infusion PTCs (p <.05). The results suggest that infused testosterone positively affects performances of a repetitive mental task. The infused testosterone appeared to have less effect upon mental performances and upon LH suppression in subjects with high post-infusion PTCs. These subjects also appear to have had less long-term effect from their own endogenous testosterone secretion, as reflected by their significantly poorer pubic hair development (p<.005).