Salivary Melatonin as a Circadian Phase Marker: Validation and Comparison to Plasma Melatonin

Abstract

There are many situations in which it would be useful to know the phase state of the biological clock. It is recognized that measurement of melatonin levels can provide this information, but traditionally blood has been used for the analysis, and there are many problems in extending the measurements into the home or field situations. The aim of this study was to develop and validate a salivary melatonin radioimmunoassay and to compare results obtained against a plasma assay for determining the onset of melatonin secretion. The assay developed was sensitive (4.3 pM) and required only 200 microliters of sample. A rhythm in melatonin was detected in saliva, peaking at approximately 120 pM or 30% of the plasma levels. Using an objective criterion for determining the onset of secretion (mean +/- 2 standard deviations of three daytime samples), the time of onset was shown to exhibit low intraindividual variability (coefficient of variation = 1.5%-4.3%). The time of onset determined using saliva was significantly correlated with the plasma onset (r = .70, p < .05). The onsets determined were 22:30 h +/- 22 min for the saliva and 21:50 h +/- 16 min for plasma for 17 subjects. Similarly, the acrophases of the saliva and plasma melatonin rhythms were significantly correlated. Neither posture alone nor changes in posture affected the calculation of the onset of melatonin secretion using the saliva approach. Very high saliva flow rates induced by citric acid resulted in lower melatonin concentrations compared to the gentle chewing on parafin film. These results firmly establish the use of salivary melatonin measurements for phase typing of the melatonin rhythm in humans.

Relationship between post-awakening salivary cortisol and melatonin secretion in healthy participants

“…The study did however demonstrate that melatonin secretion was related to awakening time with lower melatonin secretion observed with later awakening. This finding is consistent with the underlying circadian pattern of declining melatonin secretion from its night-time peak (Voultsios et al, 1997). Surprisingly, in contrast to other reports (Edwards et al, 2001) cortisol secretion was not associated with awaking time in this study, which may be related to the relatively small range of awakening time observed.…”

“…It was concluded that salivary melatonin reflects biosynthesis of melatonin from the pineal and that such sampling was a simple and non-invasive way of studying melatonin in human participants. Further work demonstrated no effect of change in body posture or naturalistic saliva flow rate on salivary melatonin levels (Voultsios et al, 1997).…”

“…The demonstration that melatonin is stable in saliva samples, with a circadian pattern reflecting serum (Vakkuri, 1985;Voultsios et al, 1997), together with the introduction of commercially available sensitive assay systems enables simultaneous determination of both cortisol and melatonin in the same saliva samples. The aim of the current study was to simultaneously study post-awakening cortisol and melatonin secretion from saliva samples on 2 days within the domestic setting in a population of healthy participants.…”

Temporal integration of light flashes by the human circadian system

“…The dynamic threshold was calculated as the mean of the first 3 daytime melatonin concentrations plus twice the standard deviation of these values (86). DLMO was estimated for each participant on days 15 (DLMO 15 ) and 16 (DLMO 16 ).…”

Pinealectomy in the chicken: a good model of scoliosis?

“…Radioimmunoassay utilised reagents obtained from Buhlmann Laboratories (Allschwil, Switzerland), and was performed as previously described for human plasma [23]. Sensitivity of the assay was 4.3 pM.…”