Since the publication of the second edition of The Pituitary, in 2002, there have been major advances in the molecular biology of pituitary hormone production and action and there is now a better understanding of the pathogenesis of pituitary tumors and clinical syndromes resulting in perturbation of pituitary function. There have also been major advances in the clinical management of pituitary disorders. Medical researchers and practitioners now better understand the morbidity and mortality associated with pituitary hormone hyposecretion and hypersecretion. Newly developed drugs, and improved methods of delivering established drugs, are allowing better medical management of acromegaly and prolactinoma. These developments have improved the worldwide consensus of the definition of cure of pituitary disease, especially hormone hypersecretion, and hence will improve the literature documenting the success or lack of success of various forms of therapy. The third edition will continue to be divided into sections that summarize normal hypothalamic-pituitary development and function, hypothalamic-pituitary failure, and pituitary tumors; additional sections will describe pituitary disease in systemic disorders and diagnostic procedures, including imaging, assessment of the eyes, and biochemical testing.