Primary hypothyroidism with pituitary enlargement and a visual field abnormality.

A 23 year old man presented with classical hypothyroidism of 9 years duration. This was associated with pituitary enlargement, documented on magnetic resonance imaging (MRI), and abnormal half-field visual evoked responses (VERs). Following the initiation of thyroxine therapy the pituitary enlargement and the VER abnormalities resolved. The final diagnosis was of primary hypothyroidism with secondary pituitary hyperplasia.