The glands that make up the endocrine system produce chemical messengers called hormones that travel through the blood to other parts of the body.

Important endocrine glands include the pituitary, thyroid, parathyroid, thymus, and adrenal glands.

There are other glands that contain endocrine tissue and secrete hormones, including the pancreas, ovaries, and testes.

The endocrine and nervous systems work closely together. The brain sends instructions to the endocrine system. In return, it gets constant feedback from the glands.

The two systems together are called the neuro endocrine system.

The hypothalamus is the master switchboard. It's the part of the brain that controls the endocrine system. That pea-sized structure hanging below it is the pituitary gland. It's called the master gland because it regulates the activity of the glands.

The hypothalamus sends either hormonal or electrical messages to the pituitary gland. In turn, it releases hormones that carry signals to other glands.

The system maintains its own balance. When the hypothalamus detects the rising level of hormones from a target organ, It sends a message to the pituitary to stop releasing certain hormones. When the pituitary stops, it causes the target organ to stop producing its hormones.

The constant adjustment of hormone levels lets the body function normally.

This process is called homeostasis.