Plasma immunoreactive endothelin-1 (ET-1) concentrations were measured in 44 patients with pheochromocytoma, 31 patients with essential hypertension, and 20 healthy control subjects. Plasma ET-1 concentrations in patients with pheochromocytoma were 18.2 +/- 3.2 fmol/mL (mean +/- SEM), which was significantly higher than those of essential hypertension and healthy control subjects (7.3 +/- 0.4, 7.1 +/- 0.4 fmol/mL, respectively, P < .01). Plasma ET-1 concentrations in patients with essential hypertension and control subjects were similar. In patients with pheochromocytoma, hypertensive group had higher ET-1 than normotensive group (23.0 +/- 5.5 v 12.4 +/- 2.2 fmol/mL), but the difference was not significant. In 17 patients with pheochromocytoma, the elevated plasma ET-1 concentrations (17.4 +/- 4.7 fmol/mL) returned to normal levels (7.9 +/- 0.6 fmol/mL, P < .05) after surgical resection of the tumor. ET-1 contents in the 26 tumor tissues (1.40 +/- 0.29 pmol/g) were higher than those in 7 normal adrenal medullas (0.44 +/- 0.12 pmol/g). Systolic, diastolic, and mean blood pressures were better correlated with plasma norepinephrine than ET-1 in patients with pheochromocytoma. These data indicate that pheochromocytoma might produce and secrete excessive amounts of ET-1. The hypertension in patients with pheochromocytoma is mainly catecholamine-dependent, but may be secondarily ET-1-dependent.

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The case of a 60-year

Neuron-specific enolase (NSE), an isomer of glycolytic enzyme enolase, is found exclusively in neuroendocrine cells and in neuroendocrine tumors in a considerably large quantity. Circulating levels of serum NSE were measured by radioimmunoassay in 24 normal adults, 23 patients with benign pheochromocytoma, three patients with malignant pheochromocytoma, and seven patients with medullary thyroid carcinoma. The mean serum NSE in normal adults was 5.8 +/- 1.3 ng/ml (mean +/- standard deviation [SD], and the range was 3.8 to 8.9 ng/ml). It also was normal in patients with benign pheochromocytoma (5.7 +/- 1.8 ng/ml; range, 2.2 to 9.3 ng/ml). However, serum NSE was elevated significantly (17.2 +/- 7.2 ng/ml; range, 10.4 to 27.3 ng/ml) in all three patients with malignant pheochromocytoma (P less than 0.01). In patients with medullary thyroid carcinoma the serum NSE remained within normal limits (5.5 +/- 1.7 ng/ml; range, 3.9 to 8.2 ng/ml). These results suggest that serum NSE might be a useful marker for screening of malignant pheochromocytoma.