The pineal melatonin rhythm provides a robust reference signal for the timing of the endogenous human circadian system. The rhythm in the major urinary metabolite of melatonin, 6-sulphatoxymelatonin (aMT6s), is highly correlated with plasma melatonin and provides a noninvasive method to measure circadian phase, particularly in field-based studies. In this chapter, we describe the protocol for collecting urinary aMT6s and the method used to calculate the acrophase, or peak, time as a circadian phase marker.
Keywords: 6-sulphatoxymelatonin; Circadian; Human; Melatonin; Urine.
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