Melatonin
Melatonin is a natural hormone made by the pineal gland from tryptophan and is critically involved in daily circadian body rhythms. Seasonal cycles in many species are controlled by the annually recurring changes in day length which in turn are perceived via melatonin secretion. The activity of the enzyme serotonin-n-acetyl-transferase is increased 30-60 fold during the dark with normal production of melatonin being almost exclusively at night. It has also been suggested that melatonin is a potent antioxidant, immune stimulant and inhibitor of cancer. Animal studies have shown an increased incidence of carcinogen-induced tumors in mice who had their pineal glands removed which was reversed by the addition of melatonin. In humans, melatonin functions in regulating normal sleep/wake cycles and has been used as a natural sleep aid and in treating symptoms related to jet lag. Melatonin decreases with age and its role in the aging process is being investigated. Supplementation with melatonin as a sleep aid is becoming more common but optimal effective doses have not been defined. Melatonin is highly lipophilic and salivary levels are a direct reflection of serum concentrations.

Interpretation of Results
Salivary levels of naturally produced hormones reflect the free fraction (non-protein-bound fraction) of hormones in the blood. Since peak melatonin levels occur in the early A.M., if a single melatonin level is desired, we suggest a 3 A.M. collection. If a diurnal panel is desired, specimens should be collected at 10 P.M., 3:00 A.M., 7 A.M., and 12 Noon. Normal unsupplemented melatonin ranges are outlined below. Melatonin is measured in pg/ml.

References
1) Arendt J. Melatonin. Clin. Endocrinol. 1988;29:205-229
2) Bartsch, H., Bartsch C. Effect of Melatonin on experimental tumors under different photoperiods and times of administration. J. Neural Trans. 1981;52:269-279
3) Whitson PA, Putcha L, Chen YM, Baker E: Melatonin and Cortisol Assessment of Circadian Shifts in Astronauts Before Flight. J Pineal Res 1995;18:141-147
4) Voultsios A, Kennaway DJ, Dawson D: Salivary Melatonin as a Circadian Phase Marker: Validation and Comparison to Plasma Melatonin. J Biol Rhythms 1997;12:457-466