ALDOSTERONE REGULATION IN PRIMARY ALDOSTERONISM: INFLUENCE OF SALT BALANCE, POSTURE AND ACTH

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Abstract
The response of aldosterone [ALDO] to manipulations of the renin-angiotensin and hypothalamic-pituitary-adrenal systems was studied in 13 patients with primary aldosteronism due to a single adenoma (10 patients) or bilateral hyperplasia (3 patients). The ALDO response to dietary Na restriction was small and variable, although urinary ALDO excretion increased in 9 out of 12 studies. The response of patients with hyperplasia could not be distinguished from those with adenoma. All patients were unresponsive to salt loading. By contrast, plasma ALDO fell in all patients after overnight dexamethasone (1 mg) and increased after brief (1 h) physiological ACTH stimulation. During prolonged erect posture, plasma ALDO increased in the 3 patients with hyperplasia and decreased or remained unchanged in patients with adenoma. Changes in plasma renin activity were similar in both groups. Patients with primary aldosteronism, while largely unresponsive to manipulations of Na balance, retain sensitivity to small and acute changes in ACTH. The different behavior of patients with hyperplasia to prolonged erect posture cannot be explained by insensitivity to ACTH, but could be due to a relative increase in sensitivity to angiotensin.

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