What is Melatonin?
Melatonin: Unraveling the Mysteries of the Sleep Hormone
Melatonin, a natural hormone intricately linked to our sleep-wake cycle, plays a vital role in maintaining our biological clock. While it can be found in the body, synthetic melatonin is widely available as an over-the-counter dietary supplement in the U.S.
The applications of melatonin are diverse, ranging from combating jet lag and regulating sleep cycles in individuals with non-24-hour sleep disorders, to addressing insomnia and managing shift-work sleep disorders. Our sleep-wake cycle typically involves around 8 hours of nighttime slumber and 16 hours of daytime activity.
Supplemental melatonin has garnered attention for its potential benefits in various areas, including sleep disorders and even cancer treatment. However, comprehensive studies to support these claims are still lacking. Notably, melatonin has been extensively examined for its efficacy in mitigating jet lag and other sleep-related ailments.
Naturally, melatonin levels increase in response to darkness, peaking between 11 PM and 3 AM at approximately 200 picograms per mL. Nighttime levels are roughly tenfold higher than daytime levels. This rise and fall of melatonin levels act as cues for our sleep and wake times, orchestrating our circadian rhythm.
Endogenous melatonin production commences from the amino acid tryptophan, with serotonin serving as an intermediary, before being released to receptors in the brain, eyes, and other crucial areas responsible for regulating sleep quality and wake cycles. With a relatively short half-life of about 20 to 50 minutes, melatonin is metabolized by the liver’s CYP450 enzyme system and subsequently excreted.
During summer, when days are longer, melatonin production occurs in shorter bursts, while winter sees more prolonged periods of melatonin release. The presence of light at night, such as from electronic devices, inhibits melatonin production and can disrupt sleep patterns. Aging also dampens nighttime melatonin levels, contributing to the prevalence of insomnia and early awakening among older adults.
But how exactly does melatonin work? As a lipid-soluble hormone, natural melatonin is synthesized in the pineal gland of the brain. It is produced from the amino acid tryptophan and then released into the bloodstream and cerebrospinal fluid, crossing the blood-brain barrier. Acting as a receptor agonist, it communicates with receptors in the brain and other areas to regulate sleep and wake cycles.
When taken as a supplement, melatonin mimics the effects of the body’s natural sleep hormone, inducing drowsiness typically within half an hour of ingestion. However, it’s important to consult a healthcare provider to determine the optimal dosing strategy, as taking melatonin before bedtime may not be suitable for all sleep disorders, and its effectiveness varies among individuals.
Melatonin is classified as an exogenous hormone when it is naturally produced within the body (endogenous hormone). However, melatonin supplements (exogenous hormone) are synthetically derived and readily available without a prescription in pharmacies, nutrition stores, and other retail outlets.
Before considering melatonin usage, individuals with allergies to the hormone should refrain from its use. Moreover, it is crucial to consult a healthcare provider to assess the compatibility of melatonin with any existing medical conditions, such as diabetes, depression, bleeding disorders, or the use of certain medications like blood thinners.
Pregnant women should seek medical advice before using melatonin, as its impact on unborn babies is not fully understood. Similarly, breastfeeding mothers should exercise caution, as the potential effects on nursing infants remain uncertain.