Circadian rhythms can be observed at multiple levels of analysis from gene expression to the behavior of the organism as a whole.
Sex differences have been described at each level of the neuraxis regulating circadian rhythms.
Sex differences have also been observed in downstream physiological circadian processes, i.e. the HPA axis.
The intrinsic sex differences and the different responses of gonadal steroids should be considered to better understand the role of the circadian system in health and disease in males and females.