The endocrine system is a complex collection of hormone-producing glands that control basic body functions such as metabolism, growth and sexual development. 

The amount of hormones produced by each gland is carefully balanced. Too much or too little of a certain hormone can have effects throughout the body and cause various endocrine disorders. Many of the hormones produced by the endocrine glands interact with each other to maintain balance.

The endocrine system consists of the pituitary gland, hypothalamus, pancreas, adrenal cortex, thyroid gland, parathyroid glands, and gonads.

The endocrine glands secrete the hormones they produce directly into the bloodstream. On the other hand, the exocrine glands actually secrete their substances through ducts to particular areas. Examples of exocrine glands include the salivary glands and the sweat glands. Most endocrine glands are controlled by trophic (stimulating) hormones secreted by the pituitary gland. The pituitary gland, in turn, is controlled by hormones secreted by the hypothalamus in the brain.