Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The endocrine system is the system of glands, each of which secretes different types of hormones directly into the bloodstream to regulate the body. The endocrine system is an information signal system like the nervous system, yet its effects are slow to initiate, and prolonged in their response, lasting from a few hours up to weeks. Hormones regulate various human functions, including metabolism, growth and development, tissue function, and mood. Learn more about the various diseases that can affect the endocrine system in this book.