The Plasma Aldosterone Response to Angiotensin II Infusion in Aldosterone-Producing Adenoma and Idiopathic Hyperaldosteronism*

Abstract

To determine if the adrenal sensitivity to angio-tensin II in patients with an aldosterone-producing adenoma differs from that in patients with idiopathic hyperaldosteronism, we infused graded doses of angiotensin II into 17 patients with primary aldosteronism and measured their plasma aldosterone concentrations after each dose. At a rate of 0.5 ng angiotensin Il/kg _ min, the mean increase in the plasma aldosterone concentration in the 8 patients from whom an aldosterone-producing adenoma was subsequently removed was 4 ± 2.4 ng/dl (mean ± SE), which was significantly less (P < 0.01) than the mean increase (23 ± 4.8 ng/dl) in the 9 patients with idiopathic hyperaldosteronism. The threshold dose of angiotensin II in the patients with aldosterone-producing adenoma was 1.0 ± 0.24 ng/ kg-min, significantly greater (P < 0.05) than the threshold dose (0.3 ± 0.07 ng/kg-min) in the patients with idiopathic hyperal-dosteronism. We conclude that the sensitivity of aldosterone-producing adenomas to angiotensin II is significantly less than that of the hypersecreting adrenal tissue in patients with idiopathic hyperaldosteronism. This difference in adrenal sensitivity might in part explain the difference in the response of plasma aldosterone concentrations to upright posture in these two subsets of aldosteronism with low renin activity.