Utility of salivary melatonin measurements in the assessment of the pineal physiology in newborn infants

SubjectsThe aim of this study was to assess whether salivary melatonin could be used as a reliable alternative to serum melatonin to study the pineal physiology in newborn infants.Design and methodsThe 95 newborn infants were allocated to four groups according to the time of sampling (09–11 am, 03–05 pm, 09–11 pm, and 03–05 am).ResultsThe median melatonin levels in serum and saliva were not significantly different between groups: median (interquartile range), 18.4 pg/mL (13.9–26.0 pg/mL) and 10.6 pg/mL (7.5–14.9 pg/mL); 13.3 pg/mL (11.5–19.0 pg/mL) and 9.1 pg/mL (7.8–14.2 pg/mL); 16.0 pg/mL (12.4–18.7 pg/mL) and 12.3 pg/mL (8.2–16.8 pg/mL); 13.0 pg/mL (8.8–27.4 pg/mL) and 11.2 pg/mL (7.7–16.6 pg/mL) for groups 1, 2, 3, and 4, respectively (p > 0.05). The results revealed a highly significant correlation between the serum and salivary melatonin levels (Pearson's correlation coefficient, r = 0.763; P < 0.001).ConclusionMelatonin levels in saliva reflect those in serum at any time of the day and like serum melatonin levels do not increase at night.