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.

What is Melatonin?

  • 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.

How does Melatonin affect my body?

  • 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.

Melatonin effects on sleep

  • 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.

What test measures Melatonin levels?

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.

What are normal Melatonin levels?

  • 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.


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:

  • Delayed sleep phase disorder: With this sleep disorder, you go to sleep and wake up more than two hours later than what’s typically considered a normal sleep-wake cycle.
  • Advanced sleep phase disorder: With this sleep disorder, you fall asleep in the early evening (6 p.m. to 9 p.m.) and wake up in the early morning (2 a.m. to 5 a.m.).
  • Irregular sleep-wake rhythm: This sleep disorder has an undefined sleep-wake cycle. You may take several naps during a 24-hour period.
  • Non-24-hour sleep-wake syndrome: With this sleep disorder, you keep your same length of sleep and awake time, but your internal clock is longer than 24 hours. When this is the case, the actual sleep-wake cycle changes every day, with the time being delayed one to two hours each day.


  • 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:

  • Hypogonadotropic hypogonadism: Hypogonadism is a condition in which your testes or ovaries produce little or no sex hormones. Hypogonadotropic hypogonadism is a form of hypogonadism that’s due to an issue with your pituitary gland or hypothalamus.

  • Anorexia nervosa: Anorexia is an eating disorder that involves limiting the number of calories and the types of food you eat due to an intense fear of gaining weight.

  • Polycystic ovarian syndrome (PCOS): PCOS is a hormonal imbalance caused by your ovaries creating excess male hormones.

  • Spontaneous hypothermia hyperhidrosis: This is a rare condition in which a person suddenly and for no known reason develops a low body temperature (hypothermia) without being in a cold environment and sweats excessively (hyperhidrosis).

  • Rabson-Mendenhall syndrome: This is a rare genetic condition characterized by severe insulin resistance, which causes high blood sugar (hyperglycemia) that can lead to diabetes. Rabson-Mendenhall syndrome can cause pineal gland enlargement (hyperplasia).

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