what melatonin does
Melatonin has been lovingly conserved by evolution and can be found in animals, plants, fungi and bacteria. In animals, it is described as a hormone and plays a number of important roles, the most well-known of which is the maintenance of circadian (daily) rhythms.
In many animals (including a wide range of mammals and birds), melatonin from the pineal gland is essential for the regulation of the bodyâs seasonal biology (eg, reproduction, behaviour and coat growth) in response to changing day length.