**1. Introduction**

Melatonin is a principal hormone produced by pineal cells in the pineal gland located in the cerebrum center behind the third ventricle (**Figure 1**). This endocrine gland consists of two cell types: pineal cells (which dominate and produce indolamines, mainly represented by melatonin, and peptides, such as arginine vasotocin) and neuroglia cells. The information received from neurons and modified by means

### **Key points**


Currently there are convincing data on the role of melatonin in the onset of menopause, the formation of climacteric syndrome, depression, osteoporosis, dyslipidemia, menopausal metabolic syndrome and cardiovascular diseases, and breast cancer in women in perimenopausal and postmenopausal women.

**Figure 1.** *Anatomical location for pineal body.*

**Figure 2.** *Melatonin mechanisms of action.*

of night and daylight intensity transforms in the pineal gland into chemical signals. Receiving the information about luminosity the pineal gland turns it into endocrine response by producing melatonin, which is a biogenic amine pertaining to the indole class, based on its chemical structure. Melatonin is a derivant of biogenic amine serotonin, which in its turn is synthesized from the amino acid tryptophan, received with food. Activity of ferments participating in serotonin transformation into melatonin is suppressed by lighting—that is why this hormone can be produced only during hours of darkness [1].

Melatonin is mainly released to the cerebrospinal fluid (liquor), getting from there to the blood flow and afterwards easily allocating itself in various organs and tissues due to good lipophilic properties [2]. Key effects of melatonin are connected with the action on membrane receptors—*MT*1 and *MT*2. They relate to a group of receptors

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*Role of Pineal Hormone Melatonin in a Woman's Life: From Conception to Decline of Life*

connected with G-protein. These receptors are responsible for chronobiological effects and regulation of circadian rhythm and are widely distributed in different organs and tissues. Melatonin receptor presentation in the reproductive organs and receptors to sexual hormones in the epiphysis enables drawing the conclusion that melatonin plays an important role in regulation of reproductive aspect (**Figure 2**). In the same way, the nuclear receptors of melatonin *ROR*-α/*RZR*-β have been discovered. It is evident that many immune-stimulating and antitumoral effects are

Antioxidative function of melatonin is based on the receptor action, but this hormone is able to directly withdraw free radicals without receptor actuation [3]. Russian scientists discovered that apart from epiphyseal melatonin, there is an extrapineal one that is formed in different gastrointestinal tracts and other organs: liver, kidneys, supramental capsules, gall bladder, ovaries, endometrium, placenta, thymus, white blood cells, thrombocytes, and endothelium. Biologic action of the

**2. Melatonin main physiological functions and its role in maintaining** 

During the recent years, new data on the mechanisms providing for the integral interaction among the nervous, immune, and endocrine systems have been received. Presumably, pineal gland is an integrator of such interaction, while its main hormone, melatonin, takes part in regulation of the activity of central and vegetative nervous systems, endocrine organs, and immune system. The performed investigations have demonstrated that melatonin fulfills an extremely wide range of physiological functions: biorhythmic and immunomodulatory processes, thermal control and sleep onset, and antioxidative and anti-stress effects [3]. Hormone secretion starts on the third month of infant development and reaches its peak during the first years (not later than at the age of 5). Before puberty, melatonin synthesis remains at a constantly high level [4]. During the age of 11–14, due to the fact that the pineal gland reduces melatonin production, the hormone mechanisms of sexual development are launched. The next significant reduction in activity occurs simultaneously with menopause onset—at the age of 45–60. With the aging progression, along with decrease in basal level, melatonin secretion peaks are getting lower [1]. During daytime melatonin concentration in the blood serum remains low (10–20 pg/ml), while during the night hours it grows considerably (80,120 pg/ml) and reaches its maximum value between midnight and 3–5 a.m. Melatonin secretion usually starts at 9 p.m. and terminates at 7–9 a.m. Melatonin metabolites are found in urine: 6-sulfatoxymelatonin (80–90%) and 6-hydroxyglucuronide (10–20%) corresponding to the circadian rhythm that is very close to the rhythm of melatonin secretion [5]. A new science, biorhythmology, introduced the notion of desynchronosis clinically very important—that means ill-being or pathological syndrome, which is connected with the unbalance of circadian rhythms. A degree of desynchronosis is defined by the quantity and rhythm of melatonin production during the day and night. It has been determined that when a somatic disease goes hard or aggravates, melatonin production is getting worse, and its night indicator is getting closer to the day value [6]. Disturbed melatonin secretion finds its clinical manifestation in tiredness, indisposition, sleep disorder, and sometimes aggravation of a chronic disease or even appearance of a new one. Desynchronosis condition is exemplified by jet lag syndrome caused by rapid long-distance transmeridian travel [7].

It is generally known that melatonin has an antidepressant function. However,

foreign colleagues stated disturbed circadian rhythm of melatonin secretion

extrapineal melatonin is carried out right where it is synthesized [1].

*DOI: http://dx.doi.org/10.5772/intechopen.88999*

mediated by them.

**human health**

*Role of Pineal Hormone Melatonin in a Woman's Life: From Conception to Decline of Life DOI: http://dx.doi.org/10.5772/intechopen.88999*

connected with G-protein. These receptors are responsible for chronobiological effects and regulation of circadian rhythm and are widely distributed in different organs and tissues. Melatonin receptor presentation in the reproductive organs and receptors to sexual hormones in the epiphysis enables drawing the conclusion that melatonin plays an important role in regulation of reproductive aspect (**Figure 2**).

In the same way, the nuclear receptors of melatonin *ROR*-α/*RZR*-β have been discovered. It is evident that many immune-stimulating and antitumoral effects are mediated by them.

Antioxidative function of melatonin is based on the receptor action, but this hormone is able to directly withdraw free radicals without receptor actuation [3].

Russian scientists discovered that apart from epiphyseal melatonin, there is an extrapineal one that is formed in different gastrointestinal tracts and other organs: liver, kidneys, supramental capsules, gall bladder, ovaries, endometrium, placenta, thymus, white blood cells, thrombocytes, and endothelium. Biologic action of the extrapineal melatonin is carried out right where it is synthesized [1].
