Aldosterone Suppression
Rationale: In healthy individuals, aldosterone production is inversely correlated with salt intake.1,2This test is based on the fact that aldosterone levels should be suppressed in individuals given a high salt diet. A urine aldosterone level >14 μg/24 hours after three days of a high salt diet is consistent with hyperaldosteronism.2
Protocol: The patient should consume a high salt diet supplemented with sodium chloride tablets (12 g/day) for three days. Starting on the morning of the third day, a 24-hour urine should be collected (no preservative) for measurement of sodium and aldosterone excretion. Urine sodium levels >200 mEq/24 hours to indicate adequate salt loading for proper test interpretation.1
Orderable Tests: See Comprehensive List of Procedures section for individual test information.
Note: Increasing dietary sodium chloride in patients with severe hypertension should be avoided. Potassium chloride replacement should be considered due to increased potassium excretion associated with a high salt diet.1
References
1. Young WF Jr. Pheochromocytoma and primary aldosteronism: Diagnostic approaches. Endocrinol Metab Clin North Am. 1997 Dec; 26(4):801-827. PubMed 9429861
2. Bravo EL. Primary aldosteronism. Issues in diagnosis and management. Endocrinol Metab Clin North Am. 1994 Jun; 23(2):271-283. PubMed 8070422