The pituitary gland is an endocrine gland. It is a protrusion in the lower part of the hypothalamus at the base of the brain. The pituitary gland is often called the "master gland" because it not only secretes its own hormones, but also orders other glands to produce them.

The pituitary gland is divided into two main sections: the anterior (front) lobe and the posterior (back) lobe. The hypothalamus and pituitary gland are connected by a stalk of blood vessels and nerves. Through this stalk, the hypothalamus communicates with the anterior lobe by means of hormones and with the posterior lobe by means of nerve impulses.

Hormones are not released from the pituitary gland in a constant stream. They are released in bursts, every one to three hours, and alternate between periods of activity and periods of inactivity.