Why is the anterior pituitary called the master gland?

An endocrine gland is any organ that secretes chemicals (called hormones) into the blood. The hypothalamus releases several hormones, including corticotropin-releasing hormone, thyrotropin-releasing hormone, growth hormone-releasing hormone, oxytocin, antidiuretic hormone, and a bunch of others. Because many of these hormones regulate the activity of the pituitary gland, which is often called the master regulator of the endocrine system, the hypothalamus is often considered the ultimate regulator of the endocrine system.