Abstract
BACKGROUND: Pituitary adenomas are the most common cause of pituitary enlargement and can potentially warrant surgical intervention. However, there are physiological causes of pituitary enlargement that can be reversed with hormone replacement alone. OBSERVATIONS: A 29-year-old female presented with acute onset paranoia to the psychiatry department. A computed tomography scan of the head revealed a 2.3 cm sellar mass with confirmation on magnetic resonance imaging. Testing showed a markedly elevated thyroid-stimulating hormone 1,600 µIU/mL (0.470-4.200 µIU/mL), suggesting pituitary hyperplasia. Treatment with levothyroxine replacement resulted in marked improvement in symptoms and resolution of pituitary hyperplasia on four month follow up. LESSONS: This rare presentation of severe primary hypothyroidism highlights the importance of evaluating for physiological causes of pituitary enlargement.