Mechanism: Ischemic necrosis of the part or all of the anterior and/or posterior pituitary. This may be related to shock or to arterial spasm of the small arteries supplying the pituitary.
Clinical history: Woman with recent or previous pregnancy complicated by hypotension or shock at the time of delivery, often due to severe hemorrhage. In very mild cases the implicated delivery may have occurred years or decades earlier.
Clinical findings:
(1) failure to lactate
(2) persistent amenorrhea
(3) failure for shaved hair to regrow, decreased body hair
(4) fatigue
(5) nausea and vomiting
(6) cold intolerance
(7) loss of libido
(8) new onset or worsening of psychiatric symptoms
(9) variable diabetes insipidus
Clinical findings seen postpartum in more severe cases with extensive necrosis and hemorrhage:
(9) headache
(10) hypotension
(11) visual field impairment
Laboratory findings - Mild to severe reduction of anterior and/or posterior pituitary hormones:
(1) reduced LH and FSH
(2) low prolactin
(3) hypothyroidism with low TSH (thyroid hormone levels may be normal for the first week after the ischemic event)
(4) reduced antidiuretic hormone if the posterior lobe is involved
(5) low ACTH and cortisol (ACTH IV stimulation test may be normal for a period after the event since the adrenal glands have not atrophied, but will then become abnormal).
(6) low growth hormone
(7) ideally no evidence of autoimmune endocrinopathy (Sheehan's syndrome can occur in a patient with an autoimmune disease, but lymphocytic hypophysitis then needs to be excluded)
Imaging findings: Depends on severity of injury, but may range from a small pituitary to an empty sella. Imaging studies done shortly after the inciting delivery may show hemorrhage.
Differential diagnosis:
(1) infarction of a pituitary adenoma
(2) lymphocytic hypophysitis
