The biological clock keeps itself regulated as a result of secretion of a hormone, that we call melatonin. This hormone is released when the brain receives a signal from its central signaling unit, known as Suprachiasmatic Nucleus or SCN.
Hence it is important that we clear our perception of melatonin. Circulation of this hormone in our bloodstream acts as a regulator of rest and activity cycles. Also, since, melatonin is a hormone, it is impossible to have a deficiency of melatonin, per se.
Nevertheless, the misconception surrounding melatonin as cure for insomnia or sleeplessness is erroneous. Herein, we must also have clear idea as to what causes insomnia.