These clock system regulate sleep, many functions of cells, gene expression (Clock regulated gene) and secretion of different hormones. The hormones in tern regulated many functions of body. Sleep come as an influence of hormone melatonin secreted from the pineal gland in brain. Stress hormones like cortisols and adrenaline are secreted from adrenals towards 4 AM to prepare the body for physical activities in coming morning. Like this the thyroid hormone and many more.
Jet lag is an example of short term dysfunction of central clock when one crosses many time zones of earth. One feels sleepy in the day time after arriving in a new region, as the biological clock has not adopted to the situation or physical time of that part of earth. Sometimes, sleep deprivation is due to continuous assaults on the clock following prolonged period of late night work or waking. Many late nighters get heart attack due more activity of stress hormones.
These aspects of deranged or dysfunction of central clock, perhaps has been experienced by many in their life time. What attracts the scientists is that these disturbance of clock function; and lack of synchronization between central and peripheral clocks may have wide reaching consequences.
They postulate that disruption of mutual talk between the two types of clock systems may result in initiation of cancer. This may occur due to abnormal hormonal secretion, gene expression and uncontrolled cell growth.
Much research need to follow to definitely prove it. However, it is better to follow nature and lead a normal life giving respect to day and night time.