A sensitive screening test for the pheochromocytoma component of multiple endocrine neoplasia type II (MEN-II), comparable to the calcitonin radioimmunoassay for medullary carcinoma of the thyroid (MCT), has been lacking. A large family with MEN-II was screened for pheochromocytoma measuring 24 hour urinary catecholamines as norepinephrine and epinephrine fractions. Pheochromocytomas have been confirmed at surgery in six family members and at autopsy in one. All seven have had associated MCT. In an additional six family members, MCT only has been detected. In five of the six patients treated surgically, the urinary epinephrine fraction was either the dominant or sole abnormality, and an epinephrine level above 20 μ/24 hours, by itself, was diagnostic of a pheochromocytoma. An increased urinary epinephrine fraction appears to be a characteristic feature of the pheochromocytoma of MEN-II, and measurement of this fraction is a sensitive and reliable screening test in afflicted families.
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