RESUMEN
BACKGROUND: The relevance of the age-associated decline in testosterone for cognition in elderly men is still poorly understood. One hypothesis is that testosterone enhances spatial abilities, while it might impair verbal skills. METHODS: Thirty elderly men received a single testosterone (250 mg testosterone enanthate) or placebo injection. Cognitive performance was tested before and 5 days after treatment using spatial as well as verbal tests. RESULTS: Five days after injection, testosterone and estradiol levels were still in the supraphysiologic range. In the verbal fluency task, the placebo group, but not the testosterone group, showed a practice effect. Therefore, the testosterone group performed significantly worse than the placebo group after treatment. No effects of testosterone were observed in the other verbal and spatial tasks. CONCLUSIONS: The present finding, that testosterone blocks the practice effect in verbal fluency, partly supports the general idea that sex steroids modulate performance in tests with known gender differences. Moreover it demonstrates that these effects can occur rapidly. However, beneficial effects on spatial cognition or memory might need more time to develop and/or might only occur when a less pronounced testosterone increase is induced.