MELATONIN AND ITS ROLE IN CIRCADIAN REGULATION OF REPRODUCTIVE FUNCTION (literature review)
The review shows the influence of the regulation of biological rhythms and the synthesis of the hormone melatonin on the female and male reproductive systems, as well as their participation in the pathogenesis of a number of fertility - related diseases. Introduction. Biological rhythms in living organisms have emerged as an adaptive mechanism that allows not only to respond to cyclically changing environmental parameters, but also to adapt to them in advance. In mammals, the level of brain activity (sleep - wakefulness), hormone synthesis and secretion, immune reactions, cell proliferation and apoptosis in tissues changes during the day. Diurnal (circadian) are present in almost all living individuals from bacteria to higher animals and affect the functioning of many organs and systems. Melatonin is a physiologically active compound found in most living organisms. Moreover, in vertebrates, in addition to synthesis in peripheral tissues and realization of autocrine and paracrine signal functions, melatonin is centrally produced by the epiphysis at night, and the duration of secretion depends on the duration of the dark time of day. Given the direct correlation of melatonin production with daylight hours and circadian rhythms, the systemic hormonal response consists in coordinating behavioral and physiological adaptation to the geophysical day and seasonal environmental changes. Circadian rhythms are thus caused by the daily regularity of melatonin synthesis, as well as the contrast between daytime and nighttime levels of its production. Currently, the idea of melatonin only as the main regulator of the sleep - wake cycle has significantly expanded. This hormone plays a key role in a number of important physiological functions of the body: it has powerful antioxidant, immunomodulatory, oncoprotective, antidepressant effects, and also participates in the neuroendocrine regulation of the reproductive system. Taking into account the many diverse effects of melatonin, in recent years more and more attention has been paid to its role in the pathogenesis of gynecological diseases associated with the violation of female and male reproductive functions, as well as the development of new therapeutic strategies. The research purpose is to analyze and summarize the available literature data on the role of circadian rhythms and the hormone melatonin on reproductive function. Materials and methods. Systematic review of domestic and foreign literature was carried out. Results and its discussion. Melatonin deficiency leads to desynchronosis and the development of related somatic diseases, as well as disruption of the antioxidant effect and neuroendocrine regulation of the reproductive axis. The use of exogenous melatonin improves the quality of gametes, including in IVF protocols. Conclusions. Melatonin regulates the secretion of gonadotropins in accordance with circadian rhythms. Violation of its production can lead to disorders of the functioning of the reproductive system.