Open Access Dissertation
Date of Award
Jean E. Davis
CIRCADIAN RHYTHM OF CORTISOL AND ESTRADIOL IN HEALTHY WOMEN
KARYN G. BUTLER
Advisor: Dr. Jean E. Davis
Degree: Doctor of Philosophy
Daily variation in human processes and behaviors has been identified for centuries. Study of these circadian rhythms demonstrates their role in human health. Sickness behaviors include alterations in affect, sleep quality and energy. The study of the relationship between circadian rhythms has been limited to isolated rhythms. The role of temporal relationships among rhythms has received little attention. Sickness behaviors are prevalent in many disorders including depression, cancer, and autoimmune disorders. Two hormones that have been shown to play a role in the manifestation of sickness behaviors are cortisol and estradiol. To date the role of the relationship between cortisol and estradiol circadian rhythms and sickness behaviors remains unknown. The purpose of this study is to explore the temporal relationship between the rhythms of cortisol and estradiol and its relationship to sickness behaviors. It was hypothesized that a cortisol-estradiol phase angle difference (PAD) would exist that would correlate with optimal affect, sleep quality and energy.
A small scale, comparative, correlational design was used to test the hypothesis. A sample of twenty-three university women (11 morning-types and 12 evening-types) between the ages of twenty to thirty-five were recruited from an urban university. Salivary samples were collected every two hours for a twenty-four hour period. Subjective measures of affect, sleep quality and energy were recorded. Salivary samples were assayed for cortisol and estradiol levels and fitted to a cosinor model with ultradian harmonics for each participant. Relationships between the cortisol-estradiol PAD and affect, sleep quality and energy measures were evaluated using a second degree polynomial equation. Results showed a significant correlation in affect measures (p < 0.05), but not sleep quality or energy. An optimal PAD was identified for affect at 3.6 hours.
The phase relationship between cortisol and estradiol may play a role in the development of alterations in affect which manifest in many disorders. These findings are based on a small homogeneous sample of university women. More research is needed in a larger, more heterogeneous group of women.
Butler, Karyn G., "Circadian rhythm of cortisol and estradiol in healthy women" (2011). Wayne State University Dissertations. 304.