[Differential diagnosis of pituitary enlargement].

Enlargement of the pituitary gland is heterogenous in the etiology. Common causes of pituitary enlargement are physiological hypertrophy during pregnancy, primary and secondary tumors, autoimmune hypophysitis including side effects of anticancer therapy with check-point inhibitors. Terms like hypertrophy, hyperplasia, sellar expansion and hypophysitis are commonly used to describe enlargement of the pituitary gland on MR scan regardless its etiology. The most common pathology causing pituitary gland enlargement is pituitary adenoma. Magnetic resonance imaging can differentiate pituitary tumors from diffuse enlargement due to hypophysitis in most but not all cases. Changes on imaging during time or response to pharmacotherapy might help determine the final diagnosis in uncertain cases. We present a case report of a young woman with sellar expansion due to prolonged untreated peripheral hypothyroidism mimicking pituitary adenoma. Interdisciplinary cooperation of endocrinologist, radiologist and neurosurgeon is crucial in determining the diagnosis.