Pituitary disorders include several clinically important conditions that arise because of hyperfunction. Prolactinomas, acromegaly and Cushing’s disease are discussed elsewhere in the Endocrine Disorders Chapter. Pituitary hypofunction results from destruction or pressure on the pituitary cells in the pituitary fossa. Hypofunction can affect the anterior or the posterior pituitary. Anterior pituitary macroadenomas cause anterior pituitary hormone failure when sufficient pressure occurs. Posterior pituitary failure is less common, and other causes are more likely.