Control of Plasma Aldosterone in Primary Aldosteronism: Distinction Between Adenoma and Hyperplasia

In 9 of 11 ambulatory patients with hyperaldosteronism due to aldosterone-producing adenoma (APA). plasma aldosterone fell during the morning; but in all 7 cases of idiopathic adrenal hyperplasia (IAH) standing caused an increase in plasma aldosterone. Further comparisons of the 9 cases of “typical” APA with the 7 patients with IAH showed other differences. The diurnal curve of plasma aldosterone in APA showed a decline from early morning to late evening, parallel with falling plasma cortisol, regardless of stimulation of renin by posture, sodium depletion or spironolactone. In APA, plasma aldosterone was increased after ACTH injection and decreased after dexamethasone. In IAH, although aldosterone secretion can be stimulated by ACTH, the ordinary diurnal rhythm of plasma aldosterone does not parallel plasma cortisol, and is not consistently altered by dexamethasone. Plasma aldosterone in IAH is consistently increased by standing, as well as by a low-sodium diet. After spironolactone, both PRC and plasma aldosterone are increased to a much greater extent than in the cases with APA. We conclude that plasma aldosterone in IAH is responsive to posture-related stimuli including PRC to a greater degree than in the “typical” case of APA. The diurnal rhythm of plasma aldosterone in APA is predominantly controlled by ACTH levels. These differences in the diurnal rhythm and physiological control of plasma aldosterone can aid in differential diagnosis of APA and IAH.