The secretions of the endocrine glands are called hormones. A hormone may be defined "as a chemical messenger secreted by a ductless gland, which reaches its destination by the blood stream and which has the power of influencing the activity of other distant organs.
The glands which have internal secretion and without any ducts but they release their secretions directly into the blood stream and transported to distant part of the body to act upon target cells.
Several activities of the human body like growth, reproduction and development are controlled by secretions from certain glands called endocrine glands or ductless glands. The secretions of the endocrine glands are called hormones.