Cortisol is a dynamic hormone possessing many functions outside of responding to stressful stimuli, such as the promotion of fat accumulation and regulating energy (oxidizable substrates). While cortisol has been widely studied as a biomarker of stress in relation to pubertal timing, few past studies have examined the extent to which cortisol may vary temporally as a function of pubertal development. Similarly, few studies have longitudinally assessed cortisol across puberty while also accounting for changes in body fat, weight, and growth that may confound relationships to cortisol and timing of menarche. In studies that have attempted to track changes in cortisol across puberty, there have been mixed results. Much of the mixed evidence may be explained by differences in study design both in terms of using variable measures of cortisol (from blood, urine, saliva, hair), discrepancies in pubertal measurements used (e.g., using age, pubertal development stage, clinical hormonal pubertal stage, or menarche alone) or only having capacity to sample at limited time points rather than across early to mid-puberty.
In this pilot study, I aim to 1) determine the magnitude of inter-individual variation in cortisol to understand whether a temporal trend exists for cortisol across puberty 2) investigate how cortisol and pre-menarcheal body compositional changes are associated with menarcheal timing. I will utilize previously collected urine samples to assay first-morning-void cortisol at the UW Biodemography Lab August-September 2021. Samples were collected from 51 pre-pubertal Indigenous Qom females from a community in Formosa, Argentina. Samples were collected by trained assistants from the Chaco Area Reproductive Ecology Program (CARE). Participants were 7-10 years old at first observation and followed until at least 3 menstrual cycles. The assayed urine samples will be used in conjunction with 2 simultaneously collected anthropometrics and menarcheal status. Critically, this pilot study will allow me to test lab methods for sampling and assaying cortisol and gain experience independently assaying cortisol in the UW Biodemography Lab. It will also allow me to test mixed-effects statistical modeling techniques and to mentor a volunteer student research assistant. All of these aspects of the pilot study will be essential to inform my future dissertation research, which will include additional analysis of these cortisol samples in relation to other pubertal hormonal trajectories, as well as to inform my study design and methods for examining cortisol responses among pubertal and post-menarcheal girls living in Jordan.