Melatonin and cortisol levels in humans can be used as biomarkers of our circadian rhythm. Dysregulation of our physiological clock occurs commonly in multiple pathologies and are of clinical interest for a range of physiological and psychological diagnostics. Melatonin is secreted by the pineal gland during the dark period and is suppressed by light. Cortisol is released in response to stress, diet and circadian rhythm factors, and its release is controlled principally by the hypothalamic-pituitary-adrenal axis (HPA axis). Together, these two hormones are metabolically coupled. In healthy states, when cortisol increases, melatonin typically drops; and thus, their levels are best studied in tandem. Most of the methods that have been developed so far to investigate melatonin and cortisol levels have relied on the analysis of whole blood, serum or saliva. Measurements of melatonin and cortisol concentrations in these samples, however, only reflects their concentrations at a single time point. Therefore, recent studies in our lab and others have begun to investigate cortisol levels in hair samples to obtain long-term averages which can be used to expand fixed time-point data. At present, no research has been reported which evaluates melatonin levels in hair. In this presentation, we demonstrate that melatonin concentrations can be determined in both hair and saliva samples. Thus, both melatonin and cortisol long-term averages can now be observed in the same hair sample. Evaluating both hormones in hair will provide a time-averaged record of melatonin and cortisol production that will be used to improve their use as diagnostic markers for circadian rhythm function.

Correlation between melatonin and cortisol levels in hair and their validity as biomarkers

253rd National Meeting (2017)

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