Pathophysiology
Hypertrophy and hyperplasia of lactotrophs during pregnancy results in the enlargement of the anterior pituitary, without a corresponding increase in blood supply.
Secondly, the anterior pituitary is supplied by a low pressure portal venous system.
These vulnerabilities, when affected by major hemorrhage or hypotension during the peripartum period, can result in ischaemia of the affected pituitary regions leading to necrosis.
The posterior pituitary is usually not affected due to its direct arterial supply.
A 1995 study found that 56.2% of patients with Sheehan’s syndrome experienced a loss of all pituitary hormones (with the remaining 43.8% having selective pituitary insufficiency). However, likely because the growth hormone-secreting cells are located at the periphery of the pituitary (and are therefore most likely to be affected by ischemia), all the patients had growth hormone deficiency.
Read more about this topic: Sheehan's Syndrome