BACKGROUND: Systematic investigations into the cognitive impact of estradiol and insulin in male individuals are sparse, and it is unclear whether the two hormones interact to benefit specific cognitive functions in humans. We investigated the acute effect of estradiol and insulin and of their combined administration on divergent (creative) and convergent (arithmetical) thinking as well as short-term and working verbal memory in healthy young men. METHODS: According to a 2×2 design, two groups of men (each n=16) received a 3-day transdermal estradiol (100 µg/24 h) or placebo pre-treatment and on two separate mornings were intranasally administered 160 IU regular human insulin and, respectively, placebo before completing a battery of cognitive tests; we also determined relevant blood parameters. RESULTS: Estrogen compared to placebo treatment induced a 3.5-fold increase in serum estradiol and suppressed serum testosterone concentrations by 70%. Estrogen in comparison to placebo improved creative performance, i.e., verbal fluency and flexibility, but not arithmetical thinking, as well as verbal short-term memory, but not visuospatial memory. The combination of estrogen and insulin enhanced recognition discriminability at delayed verbal memory recall; insulin alone remained without effect. CONCLUSIONS: Estrogen specifically enhances core aspects of creativity and verbal memory in young male individuals; delayed recognition memory benefits from the combined administration of estradiol and insulin. Our results indicate that insulin's acute cognitive impact in young men is limited and not robustly potentiated by estradiol. Estradiol per se exerts a beneficial acute effect on creative and verbal performance in healthy young men.
GrantsHelmholtz Alliance ICEMED-Imaging and Curing Environmental Metabolic Diseases, through the Initiative and Network Fund of the Helmholtz Association German Federal Ministry of Education and Research (BMBF) Deutsche Forschungsgemeinschaft