Melatonin is a natural hormone that’s mainly produced by your pineal gland in your brain. It plays a role in managing your sleep-wake cycle and circadian rhythm. Scientists still have a lot to learn about all of its effects on the human body.
Melatonin is a natural hormone that’s mainly produced by your pineal gland, which is a tiny gland in your brain. Your pineal gland is part of your endocrine system.
The full impact of melatonin in humans isn’t totally clear, but most research shows it helps to synchronize circadian rhythms in different parts of your body. Circadian rhythms are physical, mental and behavioral changes that follow a 24-hour cycle. The most important and well-known of these circadian rhythms is your sleep-wake cycle. These natural processes respond primarily to light and dark. Your pineal gland secretes the highest levels of melatonin during the night and minimal amounts during the day.
Melatonin can also be made synthetically in a laboratory and marketed as a dietary supplement. The U.S. Food and Drug Administration (FDA) doesn’t regulate supplements, so synthetic melatonin isn’t officially FDA-approved for any purposes or conditions. It’s important to talk to your healthcare provider or pharmacist before taking melatonin supplements.
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Researchers and scientists still have a lot to learn about melatonin and all of its effects on the human body. The main way melatonin affects your body is by playing a role in your body’s circadian rhythm and sleep-wake cycle.
Your pineal gland releases the highest levels of melatonin when there’s darkness and decreases melatonin production when you’re exposed to light. In other words, you have low levels of melatonin in your blood during the daylight hours and peak levels of melatonin during the nighttime. The longer the night, the longer your pineal gland secretes melatonin.
Because of this, melatonin has often been referred to as a “sleep hormone.” While melatonin isn’t essential for sleeping, you sleep better when you have the highest levels of melatonin in your body. However, several other factors contribute to your body’s ability to sleep and the quality of the sleep you get.
As your pineal gland receives information about the daily light-dark (day-night) cycle from the retinas in your eyes and then releases melatonin accordingly, people with blindness who can’t detect light usually have irregularly synchronized melatonin cycles leading to circadian rhythm disorders.
Melatonin also interacts with biologically female hormones. Research has shown that it helps in regulating menstrual cycles.
Pineal melatonin can also protect against neurodegeneration, which is the progressive loss of function of neurons. Neurodegeneration is present in conditions such as Alzheimer’s disease and Parkinson’s disease.
Researchers have found that people who’ve had their pineal gland surgically removed (pinealectomy) experienced an accelerated aging process. Because of this, some scientists think natural melatonin may have anti-aging properties.
Your healthcare provider can check your melatonin levels with a blood test, urine (pee) test or saliva (spit) test, but it’s not a common test.
Pineal melatonin levels vary widely based on your age and sex.
Newborn babies don’t produce their own melatonin. Before birth, they receive melatonin from the placenta, and after birth, they can receive it through breast milk. A melatonin cycle appears when they’re 2 to 3 months old.
Melatonin levels then continue to increase as your child ages, reaching peak levels right before puberty. Once puberty hits, there’s a steady decrease in melatonin levels until it evens out in the late teens. In all ages after puberty, melatonin levels are higher in women and people assigned female at birth (AFAB) than in men and people assigned male at birth (AMAB).
Melatonin levels are then stable until around age 40, followed by a decline as you continue to age. In people who are over 90 years old, melatonin levels are less than 20% of young adult levels.
Different factors cause the decline in age-related melatonin production, including calcification of your pineal gland, which is very common, and issues with light detection due to eye conditions, such as cataracts.
If you undergo a test that measures your melatonin levels, your healthcare provider will let you know if your levels are within normal ranges based on your age and sex.
The two main conditions that involve melatonin issues are hypomelatoninemia (lower-than-normal levels of melatonin) and hypermelatoninemia (higher-than-normal levels of melatonin). Several factors cause each of these conditions and are associated with other health conditions.
Hypomelatoninemia happens when you have lower-than-normal peak nighttime melatonin levels or lower-than-normal total production levels of melatonin when compared with what’s expected for your age and sex.
Hypomelatoninemia can play a role in circadian rhythm sleep disorders, which are a group of sleep disorders that all share the common feature of a disruption in the timing of sleep. Circadian rhythm sleep disorders include:
These sleeping disorders can cause a lack of sleep and disrupt the quality of the sleep you get, which can contribute to the development of the following health conditions:
Causes of hypomelatoninemia can be primary or secondary. Primary causes are factors that directly affect your pineal gland, such as damage to your pineal gland or a pineal gland tumor.
Secondary causes of hypomelatoninemia are due to environmental factors and/or medications, including:
Hypermelatoninemia happens when you have higher-than-normal peak nighttime melatonin levels, usually with an extended duration into the morning (daylight), when compared with what’s expected for your age and sex.
Most cases of hypermelatoninemia are from taking too much supplementary melatonin or melatonin-related sleep medications. Naturally occurring hypermelatoninemia is rare. The medical conditions associated with it include:
Symptoms of hypermelatoninemia include:
Studies have revealed that supplemental melatonin can improve sleep in specific cases, but it isn’t for everyone. It’s important to talk to your healthcare provider about melatonin supplements first before taking them and to be aware of issues related to side effects and proper dosages. In addition, as the FDA doesn’t regulate dietary supplements, you should be aware of the potential differences in quality from brand to brand. Studies show that this means the actual melatonin content could be below what a product claims. It also means it could be well above what the label claims, and that could lead to side effects. One study showed melatonin content found across 31 supplements ranged from 83% less than advertised up to 478% more than advertised.
In adults, studies have found that supplemental melatonin may have the most potential benefits for people who have a condition called delayed sleep-wake phase disorder (DSWPD) and non-24-hour sleep-wake disorder.
While natural melatonin does play a role in your sleep-wake cycle, several factors contribute to the quality of sleep you get, such as caffeine and/or alcohol usage, certain medications, mood disorders such as anxiety or depression, how comfortable your bed is and noise disruptions. It’s important to know that melatonin supplements aren’t a “magic pill” that can solve your sleep issues. Again, your healthcare provider can help determine if melatonin supplements are for you.
There isn’t any good evidence to support using melatonin supplements for COVID-19. Follow healthy lifestyle choices and proven prevention methods instead, such as getting the COVID-19 vaccine, effective mask-wearing and social distancing.
Melatonin supplements are possibly unsafe for people when taken frequently or in high doses when trying to become pregnant. There’s not enough reliable information to know if melatonin is safe in lower doses when trying to become pregnant.
Scientists don’t know enough about the safety of melatonin when used during pregnancy. Until they do more research, it’s best not to use melatonin supplements while pregnant or trying to become pregnant.
In addition, scientists don’t know enough about the safety of using melatonin supplements when breastfeeding (chestfeeding). It’s best not to use it.
A note from Cleveland Clinic
Natural melatonin is an important hormone for regulating your sleep-wake cycle. While several factors can negatively affect how long and how well you sleep, the amount of melatonin your pineal gland is making could be one of them. If you’re having issues with sleeping, be sure to talk to your healthcare provider. Quality sleep is very important and essential to health.
Last reviewed by a Cleveland Clinic medical professional on 07/05/2022.
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