The hormonal system and melatonin



By “hormone” we mean a chemical substance which is secreted into the bodily fluids by particular groups of cells (endocrine glands) and has an effect on other cells in the organism. Thus the endocrine glands secrete hormones which act at a distance on parts of the body referred to as target organs, stimulating them to function in their intended manner. Some hormonal effects are observable within a few seconds, whilst others may not start for up to several days, then going on to last for weeks, months or even years.
Hormonal effects are complex. A given hormone may have different effects in different tissues and in the same tissue at different times during our lives. Furthermore, some biological processes are controlled by just one hormone, whereas others involve complex interactions between several hormones.
Hormonal function involves four essential and fundamental aspects of life: maintaining balance in the internal environment, the generation, use and conservation of energy, growth and development, and reproduction.
A feature of the hormonal system is the rhythmical nature of its secretions into the bloodstream, with peaks that repeat at regular intervals which vary with age, sex and the type of hormone. The lengths of these cycles can vary from minutes to hours, days, weeks or even longer; the rhythms can also be different at different times in our lives, at different times of day and night and in different seasons, which all goes to show what a profound relationship there is between the hormonal system and the world around us. Thus the connection is established between the internal environment and its functions (through internal synchronisers) and the outside with its variations (external synchronisers), to which we must be able to adapt.
Hormones, then, are substances which act as messengers between the brain and the other cells of the body. They get the various parts of the body working together and establish the rhythms of – and the balance between – the organic functions, and have a profound influence on both cellular energy production and stress/adaptive responses. Indeed, there are many links between the hormonal and nervous systems, in particular as regards the establishment and maintenance of our biorhythms.

The biological clock which deals with these rhythms sits in a small cerebral nucleus located right behind the eyes, namely the suprachiasmatic nucleus, or SCN. The nerve cells of the SCN periodically transmit chemical messages, with around twelve hours of “uptime” for every twelve of “downtime”, in alternation. This is a rhythm which is inherent in us, and which is independent of all factors both internal and external to the organism, and for this reason the SCN is considered to be the source of the circadian (i.e. daily) rhythms of the human body.
The next step is transmitting the rhythm generated by this little nucleus (a rhythm which is programmed into our DNA, therefore) to the rest of the body, whose functions must become tuned and synchronised (i.e. adapted) to it. To that end, the SCN tells the pineal gland to produce melatonin, which circulates in the bloodstream around the body and gives it the information on which state to adopt, “on” or “off”. When the body clock is in its twelve-hour “uptime” phase, the mechanism becomes active and melatonin ( mélatonine )is produced; during the period of “downtime”, the gland ceases production.
It is important to add that we human beings are creatures of the day, and so we are programmed to be active during the daytime and to be at home in bed at night. Hence melatonin, being a hormone which encourages rest and recovery, is produced at night, with a peak at around 3 am. So we can now see that the body clock must be tuned not only with the internal environment, but also with the external world, so that the organism always receives the right messages about the time of day or night in which it finds itself (not forgetting that the SCN has a close relationship with the eyes). Indeed, when sunlight (or light from bright artificial source) falls on the eyes, a message is sent which turns the biological clock to “off”, suspending the production of melatonin. The body clock switches back on twelve hours later, and this is the signal for the pineal gland to start producing the hormone again. The gland releases melatonin ( mélatonine )into the blood, and the circulatory system conveys it to the billions of cells in the body: good-night!
To sum up, then, the melatonin ( mélatonine )flows around the whole circulation network, giving the body information about the time of day, thus keeping the two great networks of the body – the nervous and endocrine systems – in tune. The latter, in turn, regulates the functions of the various organs, precisely in relation to the time of day or night, creating that harmony which we know as health and wellbeing.
But in how many ways have our rhythms been distorted, in every moment of the day, by the habits that the modern human race has acquired? I do not believe that we can quantify quite how far we have strayed from the biorhythms which are programmed into us, and which represent the best hope our ancestors have given us for protecting our health! It is worth remembering that this all comes out in the form of discomfort or symptoms which always involve the hormonal system, and therefore the immune system too.
In the light of everything I have just discussed, the huge benefits of melatonin-based supplements must therefore be emphasized. They help rebalance our rhythms, and act as adjuvants in the treatment of most diseases or imbalances of the endocrine system. And more besides…

Dr. Maria Teresa Ventrella


Melatonine - Multilenguages section Key Melatonin