What is melatonin ?

Sleep hygiene

Melatonin is a hormone produced in a small structure in our brain called the “pineal gland.” Its main function is to provide temporal cues to our body, which is why it’s essential for the circadian regulation of our sleep. When melatonin secretion is disrupted, numerous sleep disorders can occur. Conversely, some sleep disorders can be treated with melatonin. Let’s take a closer look at this “miracle” sleep hormone.

The functioning of melatonin

The numerous biological functions of the human body are governed by circadian regulation, a physiological cycle that lasts a little over 24 hours. The primary location of our main circadian clock is the hypothalamus (specifically in a small group of neurons called the “suprachiasmatic nucleus” because it is located above the crossing of the two optic nerves). It regulates the alternation of the wake-sleep cycle, internal body temperature, secretion of certain hormones, as well as rhythms in metabolism or food intake. This clock “sets the time for our body,” yet it doesn’t work in isolation, and many factors, called “external synchronizers,” influence its cycle. The most powerful synchronizer of the circadian rhythm is the alternation of light and darkness, but physical and social activity as well as food intake also play an important role.

On its side, melatonin represents one of the essential “messengers” for our circadian clock. The secretion of this hormone aims to prepare the body for rest and sleep. Indeed, as soon as light decreases, melatonin secretion increases to shift the body into “sleep mode.” For a person with “normal” circadian regulation, melatonin levels will significantly rise around 9 pm (approximately 1 to 2 hours before the usual bedtime), and the peak release of melatonin will occur between 2 and 4 am. The secretion will then decrease, and melatonin will no longer be present during the day. It is crucial to note that melatonin secretion can be blocked or interrupted by light present during the evening or at night.

When melatonin secretion is disrupted

If melatonin is naturally produced by the body, in some cases its secretion may be disrupted. Most often, we observe a disruption in melatonin secretion due to inappropriate exposure to bright light. For example, exposure to light or screen use in the evening can delay melatonin secretion and create difficulties in falling asleep. Conversely, the absence of adequate light stimulation during the day can delay the cessation of melatonin secretion and make waking up more difficult. This is particularly true in cases of insufficient light exposure in the morning. Other situations can also be problematic, such as traveling across different time zones (jet lag), irregular work schedules, as well as decreased vision (difficulty in distinguishing different levels of brightness).

Finally, it should be noted that melatonin secretion evolves throughout our lives and that the pineal gland secretes less and less of it over time.

What to do in case of circadian rhythm disruption?

The most important thing is to maintain a regular sleep schedule while preserving the correct alternation of light and darkness in one’s environment. In practical terms, it’s necessary to limit exposure to light in the evening and protect oneself by reducing the intensity of surrounding lights and screens. Special glasses, called “blue blockers,” can be a simple way to preserve our circadian rhythm.

On the contrary, it’s important to expose oneself to light upon waking and during the morning (opening blinds, curtains, and exposing oneself to natural light). Light therapy (using high-intensity light for about thirty minutes in the morning after waking up) can be useful in some cases of circadian rhythm disruption.

There are also melatonin-based treatments that can compensate for low or shifted hormone secretion, but the implementation of this treatment and its dosage should be validated by a doctor. Therefore, avoid self-medication and prefer consultation with a specialized physician.