Activational effects of testosterone on cognitive function in men

Objectives: The effect of testosterone (T) on sexual function in men is wel l established. However, less is known about its effects on cognitive functi on. The aim of this study is to investigate the relationship between T leve ls and sex-typed cognitive abilities in both eugonadal and hypogonadal men. Design: A single-blind placebo-controlled design was employed in this stud y. Methods: Thirty healthy eugonadal men and seven hypogonadal men particip ated in the study. Eugonadal men were randomised into one of two treatment regimens: (1) active group - receiving 200 mg of T enanthate i.m. weekly fo r 8 weeks (raising T levels into the supraphysiological range) or (2) place bo group - receiving 200 mg of sodium chloride i.m. weekly for 8 weeks. The hypogonadal group received the physiological replacement dose of 200 mg T enanthate i.m. bi-weekly for 8 weeks. All groups underwent a battery of neu ropsychological tests and had circulating T measured at baseline, and at we eks 4 and 8 during treatment. Results: A significant time by group interact ion effect was found in the measure of spatial ability (i.e., block design test) indicating that the active group's performance declined significantly at week 4, compared to placebo group (F(4,64) = 3.78, P < 0.01). Conversel y, the active group performed significantly better than the placebo group i n the measure of verbal fluency (i.e., the Controlled Oral Word Association Test) at week 4 (F(4,64) = 2.54, P < 0.05). No significant changes were fo und on any of the other tests. Generally, the hypogonadal group performed l ess well than the eugonadal groups on all tests. Conclusions: These results offer support to the notion that increased T has a differential effect on cognitive function, inhibiting spatial abilities while improving verbal flu ency in eugonadal men. (C) 2001 Elsevier Science Ltd. All rights reserved.