Sheehan's syndrome

Sheehan syndrome, also known as postpartum hypopituitarism or postpartum pituitary necrosis, is hypopituitarism (decreased functioning of the pituitary gland), caused by necrosis due to blood loss and hypovolemic shock during and after childbirth.

Causes
It is a rare complication of pregnancy, usually occurring after excessive blood loss; the presence of disseminated intravascular coagulation (i.e., in amniotic fluid embolism or HELLP syndrome) also appears to be a factor in its development.

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.

Eponym
It is named for Harold Sheehan.