Plasma 18-oxocortisol levels in the patients with adrenocortical disorders

18-Oxocortisol (18oxoF) shares structural characteristics with cortisol and aldosterone and is secreted from the adrenal cortex. It has been reported that 18oxoF has weak gluco and mineralo-corticoid activities and increases blood pressure when administered to animals. We tried to clarify the characteristics of the production of 18oxoF in patients with adrenocortical disorders compared with the control subjects.

In patients with primary aldosteronism due to aldosterone producing adenoma (APA) (n = 21) and Cushing's disease or syndrome (Cushing's disease n = 13; adrenocortical adenoma n = 10), plasma 18oxoF level early in the morning following an overnight fast was evaluated as well as plasma cortisol and aldosterone levels.

The plasma 18oxoF levels were significantly higher in the patients with adrenocortical disorders than in control subjects. The ratios of 18oxoF/cortisol and 18oxoF/aldosterone were high in APA and in Cushing's disease and syndrome patients, respectively. In the control subjects and combined group of patients with Cushing's disease and syndrome, plasma 18oxoF level significantly correlated with plasma cortisol level but not with aldosterone level. However, in APA patients plasma 18oxoF level correlated significantly with both cortisol and aldosterone levels.

The production of 18oxoF was elevated as a result of the hyperactivity of 18-hydroxylase and excess cortisol production in APA patients and in patients with Cushing's disease and syndrome, respectively. An excess 18oxoF production could be playing a role in the pathogenesis of hypertension in these patients. The correlation of plasma 18oxoF levels with plasma cortisol and aldosterone levels suggests that the production of 18oxoF is more dependent on the supply of cortisol than on 18-hydroxylase activity in normal subjects and patients with Cushing's disease and syndrome.