What Is Melatonin Hormone Its Function Secretion and Regulation
Introduction:
Melatonin is a hormone mainly produced by the pineal gland that controls the sleep – wake cycle. As a dietary supplement, it is often used for the short - term treatment of depression, such as from jet lag or shift work, and is usually taken by mouth. Proof of its utility for this use, however, is not good.
Melatonin was discovered in 1958. It is sold over the counter in Canada and the United States; in the United Kingdom, it is a prescription-only medication. It is not approved by the US Food and Drug Administration (FDA) for any medical use. In Australia and the European Union, it is indicated for difficulty sleeping in people over the age of 54. In the European Union, it is indicated for the treatment of insomnia in children and adolescents. It was approved for medical use in the European Union in 2007.
Melatonin Hormone Functions:
Circadian Rhythm
Melatonin plays an important role in sleep regulation-wake cycles in animals. The level of melatonin in human infants becomes regular in about the third month after birth, with the highest levels measured between midnight and 8 am. Human production of melatonin decreases as a personages. Also, as children become adolescents, the melatonin release schedule for the night is delayed, leading to later sleeping and waking times.
Antioxidant
Among animals, melatonin plays an important role in the regulation of sleep – wake cycles. Human infants ' melatonin levels are normal in about the third month after birth, with the highest levels recorded between midnight and 8:00 am. Human melatonin output declines as a person ages. Also, when children become adults, the nightly cycle of melatonin release becomes postponed, leading to later sleeping and waking hours.
Immune System
While it is understood that melatonin interacts with the immune system, the specifics of those interactions remain unknown. The anti - inflammatory effect seems to be the most important. There were few studies designed to assess the efficacy of melatonin in the treatment of diseases.
Medical Uses:
Positions on the effects of melatonin for insomnia are mixed. An Agency for Healthcare Research and Quality (AHRQ) study from 2015 reported that proof of gain in the general population was uncertain. A study from 2017, found a modest effect on time before the onset of sleep. Another study from 2017 placed this decrease at six minutes to sleep onset but reported no correlation in total sleep time. Melatonin may also be useful in delayed sleep phase syndrome. Melatonin tends to function as well as ramelteon but costs less.
Dementia
A 2016 Cochrane review found no evidence that melatonin helped sleep problems in people with moderate to severe dementia due to Alzheimer's disease. A 2019 review found that while melatonin could improve sleep with minimal cognitive impairment, it has little to no effect after Alzheimer's onset. However, melatonin can aid to sunset.
Jet Lag and Shift Work
Melatonin is known to reduce the jet lag, especially when traveling eastward. However, if the time it is taken isn't correct, it may delay adaptation instead. Native evidence suggests the length of time people can sleep increases.
Occurrence:
As a Dietary Supplement:
Melatonin is categorized by the US Food and Drug Administration (FDA) as a dietary supplement.
Food Products:
Melatonin is categorized by the US Food and Drug Administration (FDA) as a dietary supplement.
Adverse Effects:
Naturally-occurring melatonin has been reported in foods including tart cherries to about 0.17–13.46 ng/g, bananas and grapes, rice and cereals, herbs, plums, olive oil, wine and beer.
Melatonin can lower levels of the hormone that stimulates follicles. The effects of Melatonin on human reproduction remain unclear.
In those taking warfarin, some evidence suggests there may exist a potentiating drug interaction, increasing the anticoagulant effect of warfarin and the risk of bleeding.
FAQs on Melatonin Hormone and Its Role in Human Physiology
1. What is melatonin hormone?
Melatonin is a hormone produced mainly by the pineal gland that regulates the body’s sleep–wake cycle. It is synthesized from the amino acid tryptophan and released primarily at night in response to darkness. Melatonin helps coordinate daily biological rhythms, also known as the circadian rhythm, and signals to the body that it is time to sleep.
2. Where is melatonin produced in the body?
Melatonin is mainly produced in the pineal gland, a small endocrine gland located in the center of the brain. Its production is controlled by the suprachiasmatic nucleus (SCN) of the hypothalamus, which receives light information from the retina. Although small amounts are also produced in tissues like the retina and gastrointestinal tract, the pineal gland is the primary source responsible for regulating sleep cycles.
3. What is the function of melatonin in the human body?
The main function of melatonin is to regulate the circadian rhythm and promote sleep. Its key roles include:
- Controlling the sleep–wake cycle by increasing at night
- Synchronizing biological rhythms with the light–dark cycle
- Acting as an antioxidant that protects cells from oxidative stress
- Supporting immune and reproductive functions
By signaling darkness to the body, melatonin prepares the brain and organs for rest.
4. How does melatonin regulate the sleep–wake cycle?
Melatonin regulates the sleep–wake cycle by increasing in response to darkness and decreasing in response to light. The process works as follows:
- Light detected by the retina sends signals to the suprachiasmatic nucleus (SCN).
- The SCN controls the activity of the pineal gland.
- In darkness, the pineal gland releases melatonin into the bloodstream.
- Rising melatonin levels promote drowsiness and lower alertness.
This daily fluctuation helps synchronize the body’s internal clock with the external environment.
5. Why is melatonin released at night?
Melatonin is released at night because its secretion is stimulated by darkness and inhibited by light. When light levels drop, signals from the suprachiasmatic nucleus (SCN) activate the pineal gland to produce melatonin. Exposure to bright light, especially blue light, suppresses melatonin production. This mechanism ensures that sleep occurs during the night in alignment with the natural light–dark cycle.
6. What is the role of melatonin in circadian rhythm?
Melatonin acts as a biological signal that helps synchronize the body’s circadian rhythm with the 24-hour day–night cycle. It provides information about environmental light conditions to body tissues. Key points include:
- Higher levels at night signal “biological night.”
- Lower levels during the day signal “biological day.”
- It coordinates sleep patterns, hormone release, and body temperature.
Thus, melatonin functions as a time-keeping hormone for many physiological processes.
7. How is melatonin synthesized in the body?
Melatonin is synthesized from the amino acid tryptophan through a multi-step biochemical pathway in the pineal gland. The steps include:
- Tryptophan is converted into serotonin.
- Serotonin is acetylated to form N-acetylserotonin.
- N-acetylserotonin is methylated to produce melatonin.
This synthesis is stimulated in darkness and regulated by neural signals from the hypothalamus.
8. What happens if melatonin levels are low?
Low melatonin levels can disrupt the sleep–wake cycle and lead to sleep disorders. Common effects include:
- Difficulty falling or staying asleep (insomnia)
- Disturbed circadian rhythm
- Increased fatigue and reduced alertness during the day
Low levels may result from aging, excessive nighttime light exposure, or irregular sleep schedules.
9. What is the difference between melatonin and serotonin?
Melatonin and serotonin are related hormones, but serotonin regulates mood while melatonin regulates sleep. Key differences include:
- Serotonin: A neurotransmitter involved in mood, appetite, and alertness; mainly active during the day.
- Melatonin: A hormone derived from serotonin; mainly active at night to promote sleep.
Serotonin serves as a biochemical precursor in the synthesis of melatonin.
10. Does melatonin affect other biological processes besides sleep?
Yes, melatonin influences several biological processes beyond sleep regulation. These include:
- Acting as a powerful antioxidant that protects cells from free radical damage
- Modulating the immune system
- Influencing reproductive hormones and seasonal breeding in some animals
- Helping regulate body temperature and blood pressure rhythms
Therefore, melatonin is a multifunctional hormone with roles in both circadian biology and overall physiological balance.
