Nonfunctioning pituitary adenomas: the Oxford experience.

Nonfunctioning adenomas are the second most common type of pituitary tumor. Over the past few years, our knowledge of the epidemiology, natural history, diagnosis, treatment, and recurrence rates of these tumors has improved. Here, we highlight some of these advances and speculate on future avenues of research. In addition, we describe our own experience in the clinical management of patients with nonfunctioning adenomas. Serum prolactin levels are generally <2,000 mU/l in patients with these tumors; we propose that this level be used as the cut-off to differentiate nonfunctioning from prolactin-secreting adenomas. Despite increases in size in 19% of the microadenomas we studied, none of the patients who received no intervention developed visual complications. By contrast, 50% of untreated macroadenomas enlarged and 67% of affected patients experienced worsened or new visual-field defects. Although most recurrences develop in the first 5 years, recurrence has been reported up 14 years after surgery.