Article Image

IPFS News Link • Science, Medicine and Technology

Sex hormones determine how well anesthesic works in men and women

•, By Bronwyn Thompson

Earlier studies have shown that women take longer to be 'put under', to emerge from anesthetic faster than men, and are more likely to experience rare occurrences of awareness while on the operating table. But why this is has been largely theory-based and understudied, which should not be a surprise given widespread gender bias in health care across the board.

Now, in a mouse and a human model, University of Pennsylvania researchers look to have confirmed that hormones play a key role in drug metabolism and their sleep effect, with women more resistant to the hypnotic aspects of general anesthesia.

"Anesthetics induce unconsciousness in part by impinging upon sexually dimorphic and hormonally sensitive hypothalamic circuits regulating sleep and wakefulness," the authors noted in the study. "Thus, we hypothesized that anesthetic sensitivity should be sex-dependent and modulated by sex hormones."

In a mouse study, the team found that at identical anesthetic concentrations, female mice were more resistant to the drug than males. However, when the trial was replicated on castrated mice, they had increased resistance that was in line with the females. As such, it seemed to confirm testosterone was at play in drug sensitivity.

"Anesthetic sensitivity is bidirectionally modulated by testosterone," the added. "Castration increases anesthetic resistance. Conversely, testosterone administration acutely increases anesthetic sensitivity. Conversion of testosterone to estradiol by aromatase is partially responsible for this effect."