Pituitary adenomas arise from the anterior lobe of the pituitary gland and may secrete, in poorly controlled fashion, one or more of the hormones normally produced at this site, leading to specific endocrine syndromes. Pituitary tumors may also compress or invade adjacent structures, and the function of the normal pituitary may be compromised when a sellar mass exerts pressure on the stalk or on the gland itself. Advances in radiologic imaging and in microsurgical apparatus have made pituitary tumors more amenable to treatment, with surgery the treatment of choice. Radiotherapy is used mainly to control residual tumor after incomplete excision. Remission can be obtained in up to 90% of patients with microadenomas and in about 50% to 60% of those with macroadenomas.