Pituitary gland. Light micrograph of a section through a healthy pituitary gland. The pituitary is a pea-sized organ found at the base of the brain. It is part of the endocrine system, a group of glands in the body that secrete hormones directly into the bloodstream. The pituitary is responsible for regulating and controlling all of the other endocrine glands. It secretes many hormones including those that stimulate the thyroid gland and growth hormone.