Melatonin is a hormone that is involved in inducing sleep and in other body functions related to biological rhythms.
It is secreted by the pineal gland, but can also be obtained through dietary supplements and medications.
In this article we will learn what this hormone consists of, how we can obtain it, when it is secreted, what relationship it has with biological rhythms, its functions, indications and side effects. Finally, we will also know the advantages that it presents in comparison to certain drugs.
- Related article: “The 50 main types of hormones (and what they are for)”
Melatonin: what is it and how is it obtained?
Melatonin (N-acetyl-5-methoxytryptamine) is a hormone secreted by our body , specifically our pineal gland (located in the center of the brain). This hormone is responsible for controlling the circadian rhythm of sleep (the sleep-wake cycle) which allows us to sleep. In addition, it also controls the infradian (seasonal) rhythms.
But melatonin is not only synthesized by our own body, but we can also obtain it from dietary supplements (generally in the form of tablets, which are ingested orally) or from medications.
Both supplements and drugs are marketed. In the case of being marketed as a drug, but, its indication is as follows: patients with insomnia over 55 years of age.
Functions
The function of melatonin is basically to induce sleep and regulate the circadian rhythm corresponding to the sleep-wake cycle.
In other words, it regulates circadian (daily) rhythms, but also infradian (seasonal) rhythms, as we will see below.
Biological rhythms: how do they work?
Biological rhythms are part of our body, and regulate some basic functions such as sleeping, eating, etc. These can be of three types: circadian (daily), infradian (occur less than once a day) and ultradian (occur more than once a day).
Melatonin acts on circadian rhythms , which have a daily frequency, as is the case with the sleep-wake cycle in adults (in children it is slightly different). These rhythms develop in the postnatal period, and are regulated by the suprachiasmatic nucleus, a brain structure that has the function of synchronizing behavior and bodily states to changes in the environment. In addition, it enables and favors survival.
The activity of the neurons of the suprachiasmatic nucleus is modified by the amount of light entering the retina (ie, the more light, the more discharge).
On the other hand, melatonin is also involved in infradian rhythms; these are characterized by the fact that they occur less than once a day, for example menstruation in women or hibernation.
In this case, the suprachiasmatic nucleus also exerts its function, through another structure, the paraventricular nucleus, which in turn activates the Sympathetic Autonomic Nervous System (SNA Sympathetic). Finally, after all this brain circuitry, it is the pineal gland (epiphysis) that secretes melatonin, which in turn controls seasonal (infradian) rhythms.
When do we secrete melatonin?
Melatonin release is related to sleep induction. But when does it occur?
The synthesis and release of melatonin in the brain usually occurs when it is dark or when light levels are lower; that is, especially at night. This explains why when the day ends and we go to sleep we feel sleepy. More specifically, the maximum peak of melatonin occurs in the first half of the night, and gradually declines as it goes on (during the second half).
However, there are also other times of the day when our melatonin levels are higher; especially, as we have said, when light levels are low.
Another interesting fact is that the amount of melatonin that our body synthesizes decreases over the years; This explains why older people (the elderly) have more problems falling asleep and/or staying asleep, presenting insomnia problems .
Indications
Melatonin is frequently used to treat sleep disorders, such as insomnia, jet lag, circadian rhythm sleep disorders in blind people, delayed sleep phases, and other disturbances or disorders.
1. Insomnia
Melatonin is mainly used to treat insomnia. The insomnia disorder can be initial (difficulty falling asleep), maintenance (difficulty staying asleep) or terminal (waking up very early).
Studies with melatonin in patients with insomnia show how this hormone can slightly increase sleep hours, improve sleep quality and reduce the time it takes to fall asleep.
2. Jet lag
Jet lag is another sleep disorder, in which it produces a temporary imbalance or decompensation in the biological clock (circadian rhythm) that makes the person unable to fall asleep and other alterations (malaise, dizziness, drowsiness, intestinal alterations…).
It usually occurs after a long plane trip, when changing the time of origin (to which we are accustomed) for the destination.
Studies using melatonin to treat jet lag show how it can slightly alleviate the symptoms of this disorder. It can also improve a person’s alertness.
3. Circadian rhythm sleep disorders in blind people
In blind people, melatonin is used to induce sleep at “normal” hours at night (thus regulating their sleep-wake cycle). These people, not seeing and not being able to detect the organism when it is dark and when it is not, have altered the circadian rhythm of sleep.
In this case, melatonin can be used in both blind children and adults.
4. Delayed sleep phase
When a person has a delayed sleep phase, it means that their sleep pattern is two hours or more behind their normal, healthy sleep pattern.
This means that their release of melatonin occurs two hours later than what is considered “normal”, and that this person begins to feel sleepy very late (for example at 1 in the morning). In turn, this implies that the person also gets up later, this fact being able to impair his daily functioning.
Studies with melatonin show how this hormone can reduce sleep latency (time it takes to fall asleep), both in children and in young adults with delayed sleep phase.
Contraindication
The use of melatonin is not indicated when suffering from an autoimmune disease.
Advantage
One of the advantages of melatonin is that it does not create dependency , a characteristic that most drugs prescribed to treat insomnia do have. In addition, it does not create tolerance either; that is, you do not need more doses as you take it to achieve the same effect.
And, finally, another positive characteristic of melatonin is that it does not cause excessive drowsiness when waking up, something that some drugs do (such as benzodiazepines). That is, you may not even present it or you may present it slightly.
Side effects
Melatonin, when ingested through supplements, is considered a safe product. On the other hand, even though it is synthesized in the laboratory, it is considered a fairly natural product. However, it can also cause side effects, such as: headaches, nausea, drowsiness and dizziness (these would be the most frequent effects).
As for the less frequent adverse effects that melatonin can cause, we find: irritability, slight anxiety, colic, mild tremors, confusion or disorientation, low blood pressure, depressive feelings and decreased alertness.
Bibliographic references
- Carlson, N.R. (2005). Physiology of behavior. Madrid: Pearson Education.
- Garjon, J. (2014). Melatonin for sleep disorders. Pharmacotherapeutic information bulletin of Navarra, 22(1): 2-11.
- Netter, F. (1989). Nervous system. Anatomy and physiology. Barcelona: Salvat.
To the classic question “what do you do?” I always answer “basically I am a psychologist”. In fact, my academic training has revolved around the psychology of development, education and community, a field of study influenced my volunteer activities, as well as my first work experiences in personal services.