Correlation between concentrations of melatonin in saliva and serum in patients with delayed sleep phase syndrome.

Exogenous melatonin, which can be used to treat certain circadian rhythm disorders, maximally advances delayed rhythms when administered 5 hours before the endogenous melatonin starts to increase. The time of the start of the endogenously melatonin is defined as Dim Light Melatonin Onset (DLMO). The DLMO concentration has been defined in serum to be 10 pg/ml. Because of the greater practicability of frequent saliva sampling over blood sampling, we have validated radioimmunoassay (RIA) measurements of melatonin in saliva in patients diagnosed as suffering from a typical circadian rhythm disorder: Delayed Sleep Phase Syndrome (DSPS). Based on these results we have defined the equivalent salivary DLMO concentration to be 4 pg/ml.