Pituitary adenomas are usually benign, slow-growing tumors that cause symptoms due to excess hormone release, local space-occupying effects, or both. Adenomas that secrete excess growth hormone cause acromegaly. Patients with acromegaly have numerous symptoms and signs, such as hyperhidrosis, prognathism, frontal skull bossing, thickened skin, diabetes mellitus, hypertension, sleep apnea, osteoarthritis, and headache, as well as enlargement of the hands, feet, heart, and other internal organs. Large adenomas expand the pituitary fossa and can lead to visual-field defects and interfere with the production of other pituitary hormones, such as gonadotropic hormones, thyroid-stimulating hormone, or adrenocorticotropin. Increased prolactin levels are often noted in such patients owing to cosecretion of growth hormone and prolactin (since somatotrophs and lactotrophs have a common developmental origin), pressure on the pituitary stalk, or both.