What are endocrine glands ? Mention their functions

What are endocrine glands ? Mention their functions.
A. Endocrine glands : Endocrine glands are the ductless glands. They secret complex organic substances called hormones directly into the blood. Hormones are transported through blood to different tissues. Their secretions act as biochemical messengers in the body. '
Functions : The hormones secreted by these glands play an important role in co¬ordinating various organ systems. Hormones can increase or decrease the metabolism and synthesis of substances like proteins, carbohydrates and lipids.
Irregular functioning of these glands may lead to serious diseases. The quantity of hormone required is very minimum (1/10,00,000 gram). A slight increase or decrease may brings out large, changes in the target tissue.