الفهرس 
AcknowledgmentOnly 14 pages are availabe for public view
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Abstract
The daily day-night cycle governs rhythmic changes in behavior and/or physiology of most species. These changes are governed by a biological clock. The circadian cycles established by this clock occur throughout nature. In addition, these circadian cycles can be synchronized to external time signals, but also can persist in the absence of such signals. Disruptions of the biological rhythms can impair the health and well-being of the organism
This circadian manner is widely distributed in different body systems, most prominently the endocrinal system. Endocrine system is highly organizedin time.
Circadian rhythm in human body has a significant effect on the incidence of some diseases and their severity. Furthermore, chronic circadian mal-alignment together with increased risk of diabetes, obesity, cardiovascular diseases, gastrointestinal disorders, and certain cancers.
Understanding the biological basis of these changes across the day and nightcan lead to better therapeutic modalities. This can be achieved by the chronotherapeutic approach to match the circadian rhythms of the diseases for the successful treatment.