Adrenergic receptor hyperactivity--a cause for pseudopheochromocytoma?

Two patients with classical signs and symptoms of pheochromocytoma, are described. In these two patients the 24-hr urinary excretion of dopamine, norepinephrine, epinephrine and their metabolites were normal or low, both in basal states or after attacks (spontaneous or provoked). However, the 24-hr urinary excretion of cyclic AMP was exceedingly high in one patient (13000 nmol/gm creatinine), and elevated in the second (5920 nmol/gm creatinine). Both patients were benefited by treatment with a combination of alpha and beta adrenergic blocking drugs. The first patient, after stopping treatment, developed hypertensive crisis and died. Post-mortem examination did not detect a pheochromocytoma or any other abnormality which could explain the excessively elevated cyclic AMP. In the second patient, extensive X-ray and CT examinations were negative for pheochromocytoma. A hypothesis is developed linking the symptoms and biochemical findings of both patients to an abnormality of the adrenergic receptor.