Endocrine glands are small organs that make and release hormones directly into the bloodstream.
At its simplest a hormone is a chemical messenger from one cell or group of cells to another. Hormones are released (secreted) into the bloodstream and have an effect on other parts of the body.
Hormones are found in all organisms with more than one cell, and so they are found in plants and animals. They influence or control a wide range of physiological activities such as growth, development, puberty, regulating sugar levels, bone growth and appetite.
The height a person reaches as an adult is a result of their genes as well as general health and nutrition during their years of growth. Normal growth is controlled by hormones such as growth hormone, sex hormones and thyroid hormones.