The pituitary is a small gland inside the head, behind the bridge of the nose. The pituitary is sometimes called the master gland because it plays a critical role in regulating growth and development, metabolism, and reproduction. The eye nerves sit directly above the pituitary gland. Enlargement of the gland can cause local symptoms such as headaches or visual disturbances. Pituitary tumors may also impair production of one or more pituitary hormones, causing reduced pituitary function (hypopituitarism).