Elevated plasma endothelin as an additional cardiovascular risk factor in patients with Cushing's syndrome

Background: Recently the pathophysiological role of endothelin (ET) has been presumed in a number of adrenal disorders such as primary hyperaldosteronism, pheochromocytoma and adrenocortical insufficiency. Aim: The aim of the present study was to evaluate circulating ET-1 levels in patients with endogenous Cushing’s syndrome. Methods and results: Plasma ET-1 levels were determined by highly sensitive RIA. Thirteen untreated subjects with Cushing’s syndrome were studied: eight women and five men of mean age 44.2^9.5 years (S.D.). In ten of them, Cushing’s disease had been diagnosed and three had adrenal adenomas. ET-1 was 3-fold higher in the patient group than in age-matched healthy controls (n ¼ 13): 1.59^0.78 vs 0.46^0.20 pmol/l respectively, P , 0.001. In adrenal adenoma patients, ET-1 was not significantly higher than in the Cushing’s disease subjects (1.84^0.67 vs 1.51^0.83 pmol/l respectively, P . 0.05). In three patients who died of severe cardiovascular complications, plasma ET-1 was significantly higher than in the remaining patients (2.34^0.35 pmol/l, P , 0.05). A positive correlation was found between the total cholesterol (6.94^1.75 mmol/l) and ET-1 levels in the patients with Cushing’s syndrome: r ¼þ 0.73, P , 0.02. No correlation was observed, however, between the levels of ET-1 and blood pressure (183^37/106^18 mmHg), plasma cortisol levels (455.2^74.5 nmol/l) or urinary cortisol excretion (1463^726 nmol/24 h). The successful treatment and correction of hypercortisolism in seven patients led to insignificant reduction in plasma ET from 1.34^0.69 to 0.73^0.53 pmol/l, P . 0.05. Conclusion: Our results clearly demonstrate that the ET system is activated in Cushing’s syndrome. Elevated plasma ET-1 levels probably play a role in the pathogenesis of accelerated and early atherosclerosis development in this disorder.