I. Definition/general comments
A. A rare but serious condition
1. Results from excessive catecholamine release (norepinephrine and epinephrine), usually from an adrenal medullary tumor
2. Characterized by paroxysmal or sustained hypertension
B. Tumors may arise along the sympathetic nervous system chain, as well as in the thorax, bladder, and brain.
II. Etiology/incidence/predisposing factors
A. Almost always caused by an adrenal medullary tumor, of which approximately 10% are malignant
B. Pheochromocytomas are found in less than 0.1% of hypertensive patients.
C. Familial causes account for approximately 10% of cases.
III. Subjective/physical examination findings
A. Hypertension, which may be labile
B. Hyperglycemia
C. Diaphoresis
D. Severe headache
E. Palpitations—related to supraventricular tachycardia
F. Anxiety
G. Tachycardia
H. Tremor
I. Weight loss
J. Increased appetite
K. Nausea
L. Weakness
M. Dyspnea
O. Postural hypotension
P. Mild temperature elevation
IV. Diagnostic/laboratory findings
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A. Glycosuria may be present.
B. Hyperglycemia may be present.
C. Thyroid-stimulating hormone, T4, free T4, and T3 levels are normal.
D. Plasma metanephrine testing has the highest sensitivity (96%) for detecting a pheochromocytoma, but a lower specificity (85%). High-risk patients (e.g., family history or genetic syndromes such as multiple endocrine neoplasia [MEN] 2A or 2B, von Hippel–Lindau [VHL] disease, or neurofibromatosis) should be screened in this manner. In these scenarios, a higher-sensitivity test that lacks specificity is justified.
1. A fractionated plasma-free metanephrine level may be obtained through simple venipuncture in a seated, ambulatory patient.
E. Assay of urinary catecholamines (total and fractionated), metanephrines, vanillylmandelic acid (VMA), and creatinine should suffice for all patients at lower risk for a pheochromocytoma (e.g., those with flushing spells, poorly controlled hypertension, or adrenal incidentalomas with an adrenocortical appearance), but these should be examined in all suspected patients.
1. A 24-hour urine collection is preferred, but an overnight collection may be sufficient. Collecting urine during or immediately after a crisis is optimal.
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