Sheehan syndrome refers to panhypopituitarism. It classically follows massive postpaum hemorrhage and associated hypotension. Abrupt, severe hypotension leads to pituitary ischemia and necrosis. In its most severe form, these patients develop shock due to pituitary apoplexy. In less severe forms, loss of gonadotrope activity in the pituitary leads to anovulation and subsequent amenorrhea. Damage to the other pituitary cell types may present as failure to lactate, loss of sexual and axillary hair, and manifestation of hypothyroidism and adrenal insufficiency symptoms. Ref: Hoffman B.L., Schorge J.O., Schaffer J.I., Halvorson L.M., Bradshaw K.D., Cunningham F.G., Calver L.E. (2012). Chapter 16. Amenorrhea. In B.L. Hoffman, J.O. Schorge, J.I. Schaffer, L.M. Halvorson, K.D. Bradshaw, F.G. Cunningham, L.E. Calver (Eds), Williams Gynecology, 2e.