Pituitary hyperplasia mimicking pituitary tumor.

Reactive enlargement of the pituitary gland in primary end organ failure may be indistinguishable from primary pituitary lesions in clinical presentation and on magnetic resonance imaging. The diagnosis of pituitary hyperplasia secondary to end organ failure must be based on endocrinologic investigations. Recognition of this condition and distinguishing it from primary pituitary tumors is important and may eliminate unnecessary surgery.