What is Hormones explain its role in humun body?

Hormones are chemical signals that trigger responses in another part of the body. Once secreted, hormones move through the spaces surrounding the cells and are transported by the blood stream to all parts of the body. However, hormonal action is restricted because they are able to stimulate only very specific "target" glands or tissues. Hormones are organic molecules that come in unique structures and shapes. Their target cells contain matching receptor proteins that recognize specific hormones. Once a hormone binds to a receptor protein, the shape of the receptor protein is changed, causing a given cellular activity.