The hypothalamus plays a key role in maintaining homeostatic functions that change during aging, like reproduction and sleep-wake activity. Using a nonhuman primate animal model, which has the benefit of age-related hormone changes similar to those of humans as well as being diurnal and showing consolidated sleep patterns, I have assessed age versus hormone-related changes in the arcuate (ARC) nucleus and the suprachiasmatic nucleus (SCN) that control reproduction and sleep-wake activity, respectively. In males, the SCN and ARC have rhythmic gene expression in elderly animals, which may have implications for changes in behavioral rhythms in older males. Finally, genes in the ARC of females were particularly responsive to hormone therapy, which suggests that there may be benefits of using estrogen supplementation to treat physiological changes related to reproductive function and activity patterns in older women.