What causes pituitary apoplexy?

Updated: Apr 19, 2019
  • Author: Michael S Vaphiades, DO; Chief Editor: Edsel B Ing, MD, MPH, FRCSC  more...
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Predisposing factors of pituitary apoplexy include endocrine stimulation tests, bromocriptine treatment, head trauma, pregnancy, pituitary irradiation, and, perhaps, anticoagulation. [10]

Okuda reported one woman with a giant pituitary adenoma who underwent triple bolus stimulation test with luteinizing hormone-releasing hormone, thyrotropin-releasing hormone (THR), and insulin. [11] The patient became stuporous, and computerized tomography (CT) scan revealed pituitary and subarachnoid hemorrhage (SAH). The investigators theorized that TRH-induced vasospasm may be a causative factor.

Some associate apoplexy with administration of gonadotrophin-releasing hormone. Corticotropin-releasing hormone administration was associated with pituitary apoplexy in a patient with Cushing syndrome. In one study, bromocriptine therapy was associated with high T1 signal in the pituitary tumor on magnetic resonance imaging (MRI), but none of the patients studied had clinical evidence of pituitary apoplexy. Others associate pituitary apoplexy with long-term bromocriptine therapy.

Pituitary apoplexy can occur after head trauma. This probably results from shear forces applied to the pituitary stalk with contusion, hemorrhage, and infarction of the adenoma.

Pituitary apoplexy during induction chemotherapy for acute myeloid leukemia has been reported by Silberstein and colleagues. [12]

Apoplexy has been reported after cardiac bypass surgery by Thurtell and colleagues. [13]

Brar and Garg reported a case of pituitary apoplexy in a young man who ascended to high altitude gradually, even after proper acclimatization. [14]

Pituitary apoplexy has been reported in a patient with dengue fever and thrombocytopenia. [15] Kruljac et al reported a patient with pituitary metastasis presenting as ischemic pituitary apoplexy following heparin-induced thrombocytopenia. [16]

Apoplexy may occur during pregnancy. Normally, the pituitary gland hypertrophies in pregnancy because of diffuse nodular hyperplasia of the prolactin secreting cells. This hypertrophy, combined with locally released factors, mediates vascular spasm and renders the pituitary more susceptible to infarction from compromised blood flow.

Sheehan syndrome refers to pituitary apoplexy of a nontumorous gland, presumably due to postpartum arterial spasm of arterioles supplying the anterior pituitary and its stalk. In 1937, Sheehan reported 11 cases of women who died in the puerperium, all of whom had necrosis of the anterior pituitary gland (adenohypophysis). Nine of the 11 cases had severe hemorrhage at delivery. The other 2 cases had no hemorrhage but were gravely ill prior to delivery. Usually, at least 1-2 liters of blood loss and hypovolemic shock are associated with a retained placenta. Sheehan syndrome occurs in 1-2% of women suffering significant postpartum hemorrhage.

The clinical presentation of acute pituitary apoplexy has only been reported in the literature in a minority of patients with Sheehan syndrome. The more commonly reported scenario is a woman who develops amenorrhea years later, with a diagnosis of Sheehan syndrome being made retrospectively. Notwithstanding, Sheehan syndrome is regarded as a neurological emergency and is potentially lethal.

In Sheehan syndrome, lactation failure may occur result from prolactin deficiency, and there may be amenorrhea due to gonadotrophin deficiency. In addition, in the postpartum period, shaved pubic or axillary hair fails to regrow, and waxy skin depigmentation develops.

Signs of hypothyroidism and hypoadrenalism may develop, and posterior pituitary (neurohypophysis) involvement with diabetes insipidus may occur. The less frequent involvement of the neurohypophysis probably stems from a difference in the anatomy of the vascular supply. The neurohypophysis contains an anastomotic ring of blood vessels that the adenohypophysis lacks.

The neuroimaging characteristics of Sheehan syndrome are distinctive. On MRI, the normal pituitary gland is largest in the immediate postpartum period, measuring up to 11.8 mm in height and convex in appearance. The anterior pituitary is usually hyperintense on T1-weighted images in pregnant and postpartum women when compared to controls. After delivery, the size of the pituitary gland rapidly returns to normal beyond the first week postpartum. The characteristic MRI finding in Sheehan syndrome is an enlarged pituitary gland bulging under the optic chiasm with peripheral enhancement surrounding an isointense gland; this characteristic MRI finding is called the "pituitary ring sign" (see Imaging Studies). [17]

Weisberg warns that radiotherapy is potentially hazardous in pituitary tumors with prior hemorrhagic, necrotic, or cystic changes. [18] Apoplexy may be precipitated in these cases.

Some believe that apoplexy is more prevalent in patients who produce excess pituitary hormones (eg, acromegaly, Cushing syndrome), perhaps because the tumor is fueled by the hormones. Others report that most pituitary tumors that undergo apoplexy are endocrinologically silent.

Ahmed and Semple reviewed the potential complications of pituitary apoplexy, one being mechanical occlusion of the internal carotid arteries in the cavernous sinus, and the other being vasospasm. [19] Both may result in brain ischemia.

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