Hormone is a special chemical which is originated and excreted by endocrine cell and tissue. These hormones get supplied into all the body organs by reaching in the blood system but they show their reaction on some special target cells. Target cells of different hormones are different. These are called chemical messenger. Hormones originate in a very little quantity and each hormone has a definite work. These are mainly the component of protein but there are some steroids too.
Endocrine glands keep on secreting hormones but the quantity of hormones can be less or much according to the need of the body. Presence of hormones in the body in less or much quantity is harmful for the body.