Melatonin is known as the “sleep hormone”, but its importance to the body is much wider. It affects, among others on the immune system, is a powerful antioxidant, and more recent research indicates that it can be helpful in the treatment of obesity, osteoporosis and other diseases common in older people.
Melatonin is a hormone whose level varies greatly throughout the day. It is produced mainly at night, in the pineal gland, in cells called pinealocytes. The signal for pinealocytes telling them to produce melatonin comes from the hypothalamus nucleus of the hypothalamus. The activity of these nuclei induces the release of norepinephrine, thanks to which serotonin is transformed into melatonin.
In addition to the pineal gland, melatonin also produces, in smaller quantities, e.g. retina, digestive system, bone marrow, leukocytes.
In the largest amounts melatonin is secreted between 4 and 10 years of age. During puberty, its secretion decreases, and then it remains relatively stable to around 45 years of age. After this age there is again a significant decrease in melatonin secretion and in people after 60? At the age of 70, only small amounts of this hormone are observed in the blood. Her circadian rhythm of secretion also disappears.
Melatonin and biological rhythms
The best known function of melatonin is the regulation of biological rhythms – seasonal and circadian. Seasonal rhythms are more pronounced in animals, and circadian rhythms are more important in humans, including the rhythm of sleep-wake . Melatonin is responsible for feeling drowsy, but also for reducing temperature and blood pressure at night. Thanks to its ability to shift the sleep phase, it is recommended to adjust the rhythm for shift workers and people with jet-lag. It also helps blind people who have frequent circadian rhythms and those with an accelerated or delayed sleep phase .
Melatonin as an antioxidant
During the cellular respiration taking place in the mitochondria, a certain amount of free radicals is always formed . These are mainly oxygen atoms with an unpaired electron, which in a large amount cause oxidative stress and contribute to the destruction of cellular DNA.
Melatonin reduces oxidative stress and thus prevents cell death , which is especially important in the nervous system, because all the most common neurodegenerative diseases are characterized by the extinction of nerve cells.
Studies have shown that melatonin is more effective in removing free radicals than vitamins C and E, often indicated as an example of antioxidants.
In addition to removing free radicals, melatonin also prevents their formation due to its effect on thyroid hormones . The pineal gland regulates the production of the TRH hormone, which stimulates the production of another hormone? TSH, stimulating the thyroid gland. Thanks to TSH, the thyroid secrete the hormone triiodothyronine (T3) and thyroxine (T4). Melatonin is involved in the transformation of T4 to T3, which is a more active hormone from T4. One of the functions of triiodothyronine is to provide energy mitochondria for the process of cellular respiration. If energy is too low, there remains an excess of unused oxygen, which leads to the formation of free radicals. Thanks to the regulation of thyroid hormones, melatonin prevents the formation of free radicals.
Melatonin in the prevention and treatment of cancer
By neutralizing free radicals, melatonin protects DNA against damage that may result in cancer. In addition, it can also help in the eradication of cancer. It has the ability to inhibit the proliferation of tumor cells , accelerate the apoptosis (extinction) of cancer cells, also prevent metastases and participate in the differentiation of cancer cells (transformation into other, less able to divide).
It can be particularly helpful in the prevention and treatment of hormone-dependent cancers (estrogen dependent breast cancer and testosterone-dependent prostate cancer). In patients with breast and prostate cancer, disturbances in the melatonin secretion cycle have been observed, which has the ability to regulate the level of estrogen and testosterone.
It is possible that the reason for the increased number of cancer cases in recent decades is the shortage of melatonin that occurs in modern society due to artificial lighting. In the past, when the sun was setting, the pineal gland began to produce melatonin. We are currently stopping this process and we are out-regulating the natural circadian rhythm in the lighted rooms. The hypothesis about the influence of melatonin deficiency on the formation of tumors is also supported by the fact that tumors are more common in older people, in whom the level of melatonin is lower than in young people.
Melatonin and the immune system
In addition to its antioxidant capacity and the ability to regulate the level of other hormones, melatonin may be effective in the prevention of cancer also by strengthening the immune system.
The activity of the immune system decreases with age. The activity of NK cells plays an important role in the prevention of cancer and metastases as well as macrophages and granulocytes that destroy pathogenic organisms. The lymphocyte profile also changes. The number of helper T cells that are responsible for stimulating the immune response is reduced, and the number of cytotoxic T lymphocytes that are involved in the fight against viruses and tumors is increased, which may also be responsible for transplant rejection.
Melatonin stimulates the production of macrophages, granulocytes, NK cells and helper T-lymphocytes and inhibits the production of cytotoxic T lymphocytes. It also increases the activity of NK cells and helper T-lymphocytes. In this way, it contributes to the “rejuvenation” of the immune system.
Another advantageous feature of melatonin is the prevention of damage to the immune system by corticosteroids secreted during stress.
Also observed in animals and people, seasonal changes in the functioning of the immune system, which may result from changes in the amount of melatonin produced.
Melatonin and cardiovascular system
Melatonin also has a beneficial effect on the circulatory system. It lowers the level of cholesterol in the blood , if its excess occurs and has the ability to regulate the pressure .
Melatonin in the digestive system
In the digestive system, the function of melatonin is to slow down the digestive processes, which increases the absorption of the necessary vitamins and microelements contained in the food. It is particularly beneficial to increase the absorption of zinc, which deficiency often occurs in older people, and which has a beneficial effect on the immune system.
Melatonin in the treatment of neurodegenerative diseases
Recently, the possibility of using melatonin in the treatment of neurodegenerative diseases has been studied.
The level of melatonin in patients suffering from Alzheimer’s disease has been reduced , also in people in preclinical conditions, when there are no visible symptoms. People with Alzheimer’s disease often have a disturbed sleep-wake rhythm that can regulate the intake of melatonin. Although there are only a few studies on the impact of melatonin on people with this disease, some of them indicate that melatonin may improve not only sleep but also slow down the decline in cognitive function.
Research is also being carried out on the introduction of melatonin for the treatment of Huntington’s disease and amyotrophic lateral sclerosis. Although research is currently not enough, the first ones are promising.
Conflicting results were obtained in the case of Parkinson’s disease. Some studies have shown a reduction in melatonin symptoms, while others have increased.
Melatonin in the treatment of obesity
Adipose tissue is divided into white and brown, whose function is to produce heat. Until recently it was thought that human brown adipose tissue occurs only in newborns and young children, but recent studies show that it also occurs in quite large numbers in adults. This tissue burns large amounts of calories to produce heat, thus consuming glucose and fatty acids, reducing deposition of adipose tissue. Melatonin controls the size and activity of brown adipose tissue and the transformation of white tissue into brown. Studies on the effects of melatonin on human obesity have not yet been studied, but animal studies have shown that it contributes to weight reduction, even without changing the diet.
Animal studies have also shown that deprivation of melatonin induces glucose intolerance and resistance to insulin. The same symptoms are seen in people with reduced levels of melatonin in the blood (eg in night workers, people with diabetes, older people).
The function of melatonin is also to increase the synthesis of leptin, which is responsible for suppressing appetite.
Melatonin in bone diseases
It is believed that melatonin may play a role in osteoporosis and idiopathic scoliosis (the so-called lateral curvature of the spine).
Animal studies have shown that deprivation of melatonin causes calcium deficiency, while in vitro studies have demonstrated the stimulating effect of melatonin on the differentiation of osteoblasts (osteogenic cells) and their activity. It is possible that with age, a decrease in the level of melatonin causes a shift in the differentiation of bone marrow cells from osteoblasts to adipose tissue cells.
The hypothesis about the influence of melatonin deficiency on the formation of osteoporosis is supported by the analysis of 38,000 postmenopausal women who showed that women who worked 20 or more years of night shifts had a higher risk of wrist or hip fractures than women who never worked at night.
Some data also indicate the possible role of melatonin deficiency in the development of scoliosis . Many studies have shown that deprivation of melatonin causes scoliosis in animals. The results of some studies also indicate a lower level of melatonin in people with scoliosis. Research on the role of melatonin in human scoliosis is currently scarce, but many scientists agree that it may be important in the development and prevention of this disease.
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