Primary hypothyroidism mimicking a pituitary macroadenoma.

Pituitary macroadenomas occur infrequently in children and can present with visual dysfunction or endocrinopathy. Occasionally, primary end-organ failure can cause reactive enlargement of the pituitary gland that may be clinically and radiographically indistinguishable from pituitary macroadenoma. The authors describe an example of reactive pituitary hyperplasia from primary hypothyroidism that mimicked a pituitary macroadenoma in a child. Recognition of this entity, which responds to medical therapy, is important because it can spare patients unnecessary surgery.