Discussion
The goal of the current study was to elucidate the effects of exogenous ESTWhile some studies found no significant sex differences in rsFCIn our study, the single treatment with ESTThe single OXTOverall, our results show that a single OXTThe present study has some limitations that need to be addressed in future research. We tested women during the early follicular phase of their menstrual cycle to control for changes in endogenous hormone levels. Nevertheless, in both sexes, supraphysiological EST levels were induced and it is conceivable that treatment or interaction effects would be altered at physiological EST levels occurring during the menstrual cycle. In addition, the treatment-induced EST levels were higher in women than in men, which may have contributed to the observed sex-specific treatment effects. However, the inclusion of treatment-induced changes in hormonal levels as covariates did not alter our results and importantly, the baseline levels of EST, OXT, testosterone, and progesterone were comparable between treatment groups. Yet, we cannot extrapolate our findings to other cycle phases, which involve the fluctuation of other steroid hormones, or hormonal contraceptives, as different estrogen types and dosages are used for their preparationCollectively, our results provide support for the notion that hippocampus and amygdala rsFC are modulated by sex and by the single and interactive effects of EST