Hormones {horma: to stir up/to excite/to put into action} play a very important role in our life right from our birth by regulating growth, development and reproduction in many ways and help maintain homeostasis. The moodiness of teenagers, obesity of humans and even the transformation of caterpillar into a butterfly are regulated by hormones.

Millions of people with diabetes all over the world take the hormone insulin. Hormones are also used in cosmetics to keep the skin smooth and in livestock feed to fatten cattle. So our life style, moods and emotions are also influenced by the hormones. The activities in our body are highly complex and they need to be so regulated that every activity takes place at a proper time and in a correct sequence. For example, the gastric juice, bile and pancreatic juice should be poured into the food canal only when there is food in it. Though this kind of regulation is done to some extent by the nervous system but it also brought about by hormones.