ituitary adenomas are among the most common brain tumors, with an stimated prevalence of 16% on autopsy studies. The patient advocacy rganization, Pituitary Network, recently conducted a “1 in 5” campaign, o increase public awareness of this common entity. While many patients arbor these adenomas, the lesions are nearly always benign and often symptomatic. Pituitary adenomas are classified according to size, with hose less than 10 mm considered microadenomas and those reaching 10 m or greater in size considered macroadenomas. The vast majority of atients with macroadenomas will have headaches. The most common resenting symptom for large tumors is visual field loss, because of levation and compression of the optic nerve(s) and chiasm from the umor as it grows upward from the sella turcica. Diplopia may occur, ecause of cavernous sinus invasion, with compression or encasement of ranial nerves III, IV, and VI. Pituitary tumors are divided physiologically nto secretory and nonsecretory tumors. The most common secretory umors are prolactinomas, followed by growth hormone-secreting tumors acromegaly) and adrenocorticotropin-producing tumors (Cushing’s synrome). Other hormonally active tumors, including gonadotropin—and hyroid-stimulating hormone-producing tumors, are less common.