Clinical meaning
Pituitary apoplexy is a clinical emergency caused by sudden hemorrhage or infarction within a pituitary adenoma, resulting in rapid tumor expansion within the rigid bony sella turcica. The sudden expansion compresses surrounding structures: the optic chiasm (causing acute visual loss, typically bitemporal hemianopsia), the cavernous sinuses laterally (causing cranial nerve III, IV, and VI palsies with diplopia and ptosis), and the normal pituitary gland (causing acute hypopituitarism). ACTH deficiency is the most immediately life-threatening consequence, as cortisol is essential for maintaining vascular tone and stress response. Without emergent glucocorticoid replacement, secondary adrenal crisis develops with cardiovascular collapse. Triggers include anticoagulation therapy, pituitary stimulation testing, surgery, head trauma, and pregnancy (Sheehan syndrome involves pituitary infarction from postpartum hemorrhage).
Exam relevance
Risk factors: - Pre-existing pituitary adenoma (usually macroadenoma) - Anticoagulation therapy (increased hemorrhage risk into tumor) - Pituitary stimulation testing (GnRH, TRH, CRH testing) - Recent surgery (especially cardiac surgery with anticoagulation) - Head trauma - Pregnancy/postpartum (Sheehan syndrome) - Diabetes mellitus - Hypertension - Radiation therapy to the sella