The first thing we should be clear about is, what exactly is melatonin? Melatonin is a substance (a hormone) secreted by the pineal gland in the brain that has a rapid, mild sleepiness-inducing effect. For this reason, some people buy melatonin uk for insomnia to help regulate their normal sleep cycle, although some concerns remain about its safety, especially for long-term use.
Circadian Rhythms
Your circadian rhythm can be defined as the normal daily cycles that your body goes through. During each 24-hour cycle, levels of hormones rise and fall depending on the moment of the day; your kidneys produce more urine during the day and less at night; and your body temperature is higher at sometimes of the day than others (it tends to fall just before we go to sleep, for example). These are normal, rhythmic changes that help us be alert and functioning when we need to be, and to rest and rejuvenate at other times.