Hypertension may be attributable to various disorders involving the central or peripheral adrenergic (catecholamine) pathways. Pheochromocytoma is the best known of these disorders, but many syndromes mimic the clinical features of this tumor. In adreno-medullary hypertension, cardiovascular tissues are stimulated by activation of alpha or beta adrenergic receptors, or both. Specific diagnosis of adreno-medullary hypertension depends on careful clinical assessment and selection of sensitive and specific biochemical tests for measuring the catecholamines and their principal metabolites in urine or plasma. If such tests indicate the presence of a chromaffin cell neoplasm, accurate localization (imaging) is provided by computed axial tomography (CAT) or magnetic resonance imaging (MRI). Adreno-medullary hypertension is effectively controlled, pharmacologically, by alpha and beta receptor antagonists, which may be given intravenously for emergencies. Excess catecholamine synthesis by pheochromocytomas can be reduced by methyltyrosine. Surgical cure of pheochromocytomas can be expected in most instances, but long-term surveillance for recurrent tumors, some of which may be malignant, is needed. Chemotherapy can reduce the tumor bulk of a malignant pheochromocytoma. Recent use of molecular biology techniques may be helpful in early detection of malignant transformation.
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