Recognizing and Intervening in Pituitary Apoplexy

Elizabeth Zink, MS, ACNP, CCRN, CNRN

Disclosures

Topics in Advanced Practice Nursing eJournal. 2005;5(4) 

In This Article

Pituitary Pathology

Pituitary Tumors

The Central Brain Tumor Registry of the United States reports the incidence of pituitary tumors to be 6% of all brain tumors.[3] Tumors involving the pituitary gland typically affect the anterior pituitary, or adenohypophysis, are typically benign, and may or may not secrete hormones. The pathologist determines the specific type of tumor and hormones that are secreted by examining specimens obtained during surgery. Although these tumors are generally benign in their histologic make-up, they are space occupying lesions that may exert excess pressure on and endanger function of adjacent structures such as the optic chiasm and cranial nerves III, IV, V (ophthalmic and maxillary divisions), and VI. In addition, tumors may invade the surrounding bony structures of the skull base and vascular structures, such as the cavernous sinus.

The World Health Organization recognizes 14 subtypes of pituitary tumors and classifies them according to criteria: clinical presentation; serum hormone levels; tumor size, extension, and invasiveness; histopathologic findings; hormone concentrations detected during immunocytochemistry; and specific features of tumor cells.[4] Two of the 14 subtypes of pituitary tumors, null cell adenomas and oncocytomas, are tumors that are inactive and do not secrete hormones. Roughly half of patients who develop pituitary apoplexy have this type of tumor. Microadenomas (pituitary tumors < 1 cm in diameter) predominate pituitary tumor subtypes, whereas macroadenomas (> 1 cm in diameter) make up the remainder.[5]

Pituitary Enlargement

Several conditions, including increased hormone secretion and inflammation, can lead to pituitary gland enlargement ( Table 2 ). Pregnancy commonly causes the pituitary gland to enlarge by approximately 136% of the prepregnancy size because of elevated hormone production and secretion, which is necessary to support pregnancy and prepare for childbirth.[6]

Sheehan's syndrome is a rare condition seen during pregnancy or subsequent to delivery in which the pituitary gland becomes infarcted, usually as a result of postpartum hemorrhage and hypovolemic shock causing a state of acute systemic hypoperfusion. Sheehan's syndrome may also occur when the enlarged pituitary gland outgrows the sellar space, placing pressure on the pituitary vascular supply, thus reducing blood flow and causing infarction. This condition is rare in developed countries because of the rich medical resources and aggressive medical care provided to women during childbirth, which mitigates postpartum hemorrhage and associated hypoperfused states.[6]

Infarction may transform into hemorrhage. In some cases, primary hemorrhage arises in the enlarged pituitary for unclear reasons. Another rare condition presenting most often during pregnancy is lymphocytic hypophysitis, an infiltrative process through which white blood cells accumulate within the pituitary, causing an abscess resulting in enlargement and inflammation. This process is thought to be autoimmune-mediated and self-limiting without medical intervention. However, lymphocytic hypophysitis can mimic a pituitary adenoma on radiographic imaging, which may prompt surgical treatment if symptoms are severe.

Nelson's syndrome is another rare condition resulting in pituitary enlargement. This condition may occur after an adrenalectomy. Rapid enlargement of the pituitary gland in this setting may be a precipitating cause of pituitary apoplexy, unique to this particular patient population.

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