Objective: With increasing use of computed tomography and magnetic resonance imaging, pituitary adenomas are being discovered incidentally with increasing frequency. However, limited data are available concerning the clinical importance and natural history of such 'incicentalomas'. We have undertaken a prospective study to investigate changes in adenoma size and endocrine and visual function in patients with incidentally discovered intrasellar masses.
Patients and methods: Our study included 67 patients with incidentalomas of the pituitary gland during a 5-year period (1992-96). 50 of these patients were followed up prospectively over a mean period of 2.7 years. Initially, all patients underwent endocrine testing and ophthalmological examinations as well as magnetic resonance imaging or computed tomography scans. These investigations were repeated after 3 months and then annually.
Results: 42 (62.7%) out of 67 patients with incidentalomas had microadenomas whereas 37.3% had macroadenomas. Macroadenomas were found more frequently in men (52.2%). Visual field defects could be documented in 4.5% of the patients. Partial deficiency of anterior pituitary function was present in 14.9%. Eight patients (11.9%) had prolactinomas. An increase in adenoma size was detected in 3.2% of the microadenomas and in 26.3% of the macroadenomas within the follow-up period.
Conclusion: Macroadenomas and hormone secreting adenomas are not uncommon in patients with pituitary incidentalomas. Macroadenomas should be closely monitored for tumour enlargement. All patients should undergo biochemical assessment and ophthalmological examination, since endocrine dysfunction or visual field defects may be present at the time a pituitary incidentaloma is detected.