The lack of normal catecholamine responses in patients with pheochromocytomas

Because of divergent reports of catecholamine secretion with the patient positioned upright in patients with pheochromocytomas, we have measured plasma norepinephrine (NE) and epinephrine (E) by radioenzymatic assay, both in normal subjects (eight) and in patients with pheochromocytomas (12) during three conditions that stimulate release of catecholamines. Standing (S), isometric hand exercise (H), and hand immersion in cold water (C) resulted in a significant rise in plasma NE concentrations in normal subjects; plasma E concentrations rose only at 6 minutes of S. Average rises (percentage +/- SEM) for NE were 68 +/- 3 (S), 22 +/- 6.5 (H), and 46 +/- 4.1 (C); for E, 33.1 +/- 12.2 (S). On the other hand, in patients with pheochromocytomas, no significant changes from basal NE (except at 2 minutes S) or E concentrations were seen during S, H, or C. Average percentage changes (+/- SEM) for NE were 18.2 +/- 7.8 (S), 11.6 +/- 3.6 (H), and -17.9 +/- 8.3 (C). There was a significantly lower percentage response of plasma NE concentrations in patients during S (P less than 0.001) and C (P less than 0.01), compared with that in normal subjects. The NE responses in two patients with metastatic pheochromocytoma after adrenalectomy were similar to those seen in patients with benign tumors in the adrenal medulla. Finally, a reciprocal relationship between plasma E and NE concentrations seen in normal subjects during S was not seen in the patients. Our findings support the conclusion that pheochromocytomas are not functionally integrated with or innervated by the sympathetic nervous system.