Endocrinology is a branch of medical biology deals with the endocrine system, related diseases, and its specific hormones.

The endocrine system consists of several glands, all in different parts of the body that secrete hormones directly into the blood rather than into a duct system. Hormones have many different functions and modes of action. One hormone may have several effects on differently targeted organs, and, conversely, one targeted organ may be affected by more than one hormone.

Endocrinology