Date of Award
Developing an endocrine-based laboratory exercise for undergraduate students is challenging because of the limitations that are characteristic of endocrine processes. These laboratory exercises often involve invasive methods and expensive biochemical analysis. They are also time consuming because of the slow-acting endocrine responses. A potential endocrine-based exercise that can be completed in 2-3 hours, is non-invasive, and at a low cost is a salivary assay. This assay is not without drawbacks, however, including sample collection outside the laboratory classroom. Cortisol is a hormone that is accessible in saliva and provides some insight into the Hypothalamic-Pituitary-Adrenal Axis (HPA Axis), also known as the stress cascade. Stress has been shown to evoke cravings for foods high in sugar content. Cortisol is often released in response to a stressor and tends to follow a circadian rhythm, tending to be higher in the morning and lower at night. Validation of the procedure for evaluating this circadian rhythm in an undergraduate laboratory setting was achieved by allowing 16 students to provide night and morning saliva samples by self-collecting samples at home. The other 84 students were split into groups to examine the effect of sugar intake on cortisol levels by eating snacks with varying amounts of sugar. These sugar treatment groups consisted of a control group (0g), low (<1g), medium (14g), and high (26g) sugar consumption. Samples were analyzed with a salivary cortisol ELISA assay kit procedure and with a microplate reader to obtain absorbance measurements. A paired t-test supported significance (p<0.001) between morning and night samples of cortisol. ANCOVA was used to determine a significance (p<0.001) found between samples in all sugar treatment groups. Therefore, sugar was shown to have an effect of increasing cortisol levels. The methods were successful in the ability to be integrated into an undergraduate laboratory curriculum by limiting the time and invasiveness of an endocrine-based laboratory approach to teaching students.
Guy, Charmin C., "Development of a Novel Salivary Cortisol Laboratory Experiment for Undergraduate Physiology Students" (2018). Honors Theses. 184.