Melatonin measurement is used to investigate sleep disorders and the body's reactions to stress.
Melatonin is a compound secreted mainly by the pineal gland but synthesized also in many other tissues and cells. In humans, nocturnally peaking oscillations of melatonin are involved in sleep-wakefulness where melatonin concentrations are lower during the day.
In recent years, the role of melatonin and its metabolites have been identified as potent, broad-acting antioxidants and free radical scavengers in addition to playing a role in the upregulation of antioxidant enzymes. Melatonin levels in plasma are paralleled by corresponding variations in saliva where the saliva concentrations are about 30% of that found in plasma. Measurement of salivary Melatonin is advantageous, especially to avoid invasive venipuncture procedures.
Melatonin is a hormone that also acts as a neurotransmitter. It is synthesized in the epiphysis and is derived from the amino acid tryptophan with the intermediate molecule serotonin. Melatonin levels follow a daily (circadian) rhythm in response to the light / dark cycle (melatonin and light occur at opposite times). Endogenous melatonin production begins about 2 hours before bedtime, provided the light is dim.
Many people know about melatonin because of its effect on sleep. Melatonin helps positively by influencing the initiation and maintenance of quality sleep cycles while disorders in the rhythm of melatonin secretion, commonly referred to as phase shift, may present clinically as sleep disorders.
Although better known for its relationship to sleep, melatonin plays many other clinically important roles. Melatonin is a powerful antioxidant found in almost every cell in the body. It stimulates the function of the immune system and reduced levels are observed in cancer patients, as well as in people with reduced CNS function. Melatonin can help with weight loss and improve mood and has been shown to have anti-aging properties. In addition, the antioxidant activity of melatonin can protect the egg at ovulation, optimize progesterone secretion, and seems to increase the success rate of artificial insemination.
Melatonin and cortisol are inversely related: when melatonin levels are low, cortisol levels should be high, and vice versa. However, as disturbances in the daily cortisol secretion rhythm may be observed, disturbances in the melatonin secretion rhythm may also occur. The circadian rhythm of melatonin secretion is influenced by various factors. For example, a decrease in melatonin levels is observed with increasing age, exposure to blue light (such as that commonly emitted by television screens and computers), and some medications including benzodiazepines and antihypertensives (beta-blockers). Some antidepressants and antipsychotics can alter melatonin rhythm, as can strenuous exercise.
Taking melatonin supplements can be especially helpful for people who are working in shifts or suffer from jet lag.
Therapeutic interventions to optimize melatonin levels:
- Implement a consistent sleep schedule
- Increased exposure to light during daylight hours
- Reduce the amount of light exposure (especially blue light) during the evening hours
- Taking melatonin supplements
Taking immediate-release melatonin supplements may be helpful for people with difficulty sleeping and low evening melatonin levels. Prolonged-release supplements release melatonin gradually over 5-8 hours and may be more beneficial for those who have waking episodes during sleep. It is generally recommended to take a melatonin supplement 30-60 minutes before bedtime (available in various forms: sublingual, drops, and chewable) which may have a faster effect than capsules, and extended-release formulations that affect melatonin levels beyond immediate-release formulations.
Melatonin supplementation is not associated with the suppression of the body's ability to produce melatonin. Even at doses up to 50 mg, melatonin has not shown addictive properties or suppression of endogenous production.