Searching for Pheochromocytoma: A New and Better Test?

Pheochromocytoma. The term calls to mind fundamental problems in clinical medicine, such as secondary hypertension, screening for rare but dangerous diseases, management of high-risk patients, and short-hand mnemonics for “Board” questions (for example, the Rule of 10). To the medical student and resident, pheochromocytoma is a rare cause of secondary hypertension, a “zebra” whose hoofbeats are almost never heard among the herd of ordinary patients with hypertension encountered in the medical clinic or in-patient services. The specialist often deals with pheochromocytoma after a diagnosis is made elsewhere by a discerning or lucky physician (serendipity still helps us in this regard).

When undetected, pheochromocytoma can maim or kill. Therefore, infrequent as the disease may be, accurate, safe, and feasible screening to find these tumors remains an important goal for the primary care physician, the clinical researcher, and the subspecialist alike. This crucial need is addressed by Lenders and colleagues in this issue [1]. Excess catecholamines released into the circulation by a pheochromocytoma cause the clinical manifestations of the disease. Increased plasma concentrations of norepinephrines or epinephrines or both are found in most but not all patients with these neoplasms. However, high plasma concentrations of catecholamines may be found in other disorders, and the limited sensitivity and specificity of measurement of plasma catecholamines for diagnosis of pheochromocytoma has been well established [2, 3].

Enzymatic metabolism of catecholamines proceeds both by the o-methylation pathway (yielding normetanephrine and …