The Influence of Non-energetic Stressors on Human Menstrual Function

The Reproductive Suppression Model posits that due to the high cost and failure rate of human reproduction, the female body maximizes lifetime reproductive fitness by suppressing reproduction during poor conditions (where likelihood of offspring survival is low) until conditions are more favorable. The hormonal mechanism for this suppression when calories are scarce and the female body is in low energy availability (LEA) has been studied. However, the mechanism for this suppression in the presence of stressors unrelated to low energy availability, but which could still negatively impact offspring survival, is much less clear. The investigators define such stressors, which do not impact energy state or energetic demands, as "non-energetic stressors." Thus, the aim of this study is to determine if non-energetic stressors drive reproductive suppression in humans. The investigators will assess this by testing the impact of a stress intervention on the stress hormones cortisol and norepinephrine, and in turn if the levels of these stress hormones predict the levels of sex hormones associated with the menstrual cycle. Finally, the investigators will assess if changes in stress hormones change total and basal energy expenditure.