170 - Pituitary Apoplexy

The posterior lobe is an extension of the hypothalamus and secretes two hormones: antidiuretic hormone (or arginine vasopressin) and oxytocin. The pituitary stalk and the portal vessel pass through a small diaphragm that separates the sella turcica from the middle fossa. This anatomic arrangement places the pituitary at risk for infarction or hemorrhage when a mass increases pressure in the sella or compresses the stalk and vessels. Higher intrasellar pressures are associated with poor outcomes. Pituitary tumors are common and many are asymptomatic. They are classified by size (microadenoma, <10 mm; macroadenoma, >10 mm) and by the hormone produced. Of tumors that cause clinical symptoms, the most commonly secreted hormones are PRL, which leads to hypogonadism; GH, which promotes acromegaly; and ACTH, a cause of Cushing disease. Tumors involved in apoplexy are typically nonfunctional and unsuspected macroadenomas. In patients undergoing an endocrine stimulation test for hypogonadism, hypothyroidism, or adrenal insufficiency, apoplexy may occasionally develop secondary to stimulation of a macroadenoma. Treatment of a pituitary tumor can also precipitate apoplexy, particularly in cases of surgery, irradiation, or bromocriptine administration. Other reported risk factors include pregnancy (Sheehan syndrome), head trauma, recent cardiac surgery, anticoagulation, hypertension, diabetic ketoacidosis, and ovarian stimulation medications. Most patients with pituitary apoplexy have no identifiable risk factor. Apoplexy may occur in normal glands.