Turnover and Metabolism of Catecholamines in Patients with Pheochromocytoma*

Abstract

The 24-hour urinary excretions of free norepinephrine (NE) and epinephrine (E), of total normetanephrine plus metanephrine (NMN plus MN), and of 3-methoxy-4-hydroxy-mandelic acid (VMA) were measured in 24 patients with pheochromocy-toma. In addition, 23 tumors were assayed for NE and E, and 9 for NMN plus MN. The results demonstrate that individual tumors vary widely in their rates of production and turnover of catecholamines. In some the catecholamine store is replaced at a rapid rate, and a relatively pure infusion of NE (and sometimes E) is secreted into the host; these tumors are usually small in size (less than 50 g). In other tumors the catecholamine store is turned over more slowly, and a considerable portion of the NE and E synthesized is apparently metabolized directly in the tumor; these neoplasms are usually large (over 50 g). The concept is presented that the intracellular binding of catecholamines, the regulation of catecholamine synthesis, and the activity of catecholamine-degrading enzymes may all be abnormal in the pheochromocytoma cell.