Aldosterone regulation during saline infusion: usefulness of aldosterone/cortisol ratio in the diagnosis of aldosterone-producing adenoma.

1. Saline infusion was performed in normal subjects, in essential hypertensives and in patients with aldosterone-producing adenoma (APA), with serial measurements of plasma aldosterone, cortisol and atrial natriuretic peptide (ANP). The effect of recumbency alone was also observed in the normal subjects. 2. Plasma aldosterone after saline infusion was less than 7 ng per 100 ml in the essential hypertensives and normal subjects, but greater than 9 ng per 100 ml in the patients with APA. 3. The aldosterone/cortisol ratio in normal subjects and in essential hypertensives was unchanged or fell during saline infusion, but rose in five of eight patients with APA. 4. Thus, an increase in aldosterone/cortisol ratio after saline infusion appears to be diagnostic of APA, but its absence does not exclude it.