MELATONIN: THE MULTIFACETED HORMONE

Melatonin is a hormone secreted by the pineal gland and its main biological function is to regulate the circadian rhythm. Melatonin synthesis varies according to light and dark conditions. While melatonin production is suppressed in the light environment, melatonin production increases in the dark environment. Melatonin acts through different mechanisms. One of these mechanisms is receptor-dependent signal transduction mechanism. Two types of receptors have been identified as melatonin receptor, melatonin receptor 1 and melatonin receptor 2. Through these mechanisms of action, in addition to circadian rhythm regulation, melatonin has various physiological and pathophysiological roles, including sleep cycle regulation, antioxidant and anti-inflammatory effects, immune system modulation, effects on cancer, cardiovascular system, central nervous system and neurodegenerative diseases. In this review, it is aimed to examine the roles of melatonin in physiological and pathophysiological processes.