Clinically non-functioning pituitary adenoma

Abstract

Non-functioning pituitary tumors are relatively common. A large number of these tumors are incidentally found pituitary microadenomas (<1 cm) and are usually of no clinical importance. Those tumors that require treatment are generally macroadenomas and come to medical attention because of mass effect and/or hypopituitarism. Visual field defects are present in roughly 70% of patients with non-functioning macroadenoma at the time of diagnosis and the majority of these patients have at least growth deficiency and hypogonadism. By immunocytochemistry, the large majority of these tumors are glycoprotein producing and less commonly they are non-functioning somatotroph, lactotroph or corticotoph adenomas. In contrast to the immunocytochemistry results, only a minority of these tumors actively secrete intact gonadotrophs or glycoprotein subunits. Therapy is directed at eliminating mass effect and correcting hypopituitarism. There are anecdotal reports of tumor shrinkage during therapy with either dopamine agonists or somatostatin agonists; however tumor response to medical treatment is not reliable. For most patients, transphenoidal resection of the tumor is the preferable primary treatment. Surgery improves visual defects in the majority of patients and a lesser number will recover pituitary function. In the past, pituitary radiation was commonly administered following pituitary surgery; however the need for routine radiation has recently been reevaluated. Although tumor recurrence at 10 years post surgery may be as high as 50%, few patients with recurrence will have clinical symptoms. Close follow-up with surveillance pituitary scans should be performed after surgery and radiation therapy reserved for patients having significant tumor recurrence.