Here's why:

* It controls other glands: The pituitary gland produces hormones that regulate the activity of other endocrine glands, such as the thyroid, adrenal glands, and ovaries or testes.

* Direct effects: It also produces hormones that have direct effects on the body, such as growth hormone and prolactin.

* Influence on many bodily functions: The pituitary gland's influence extends to a wide range of bodily functions, including growth, metabolism, reproduction, and stress response.

However, it's important to note that the pituitary gland itself is controlled by the hypothalamus, a part of the brain. The hypothalamus sends signals to the pituitary gland, telling it when to release hormones. So, while the pituitary gland is a key player in the endocrine system, it's not truly independent.