Hypokalemia may Mask Primary Aldosteronism: A Case Series

ABSTRACT Objective: To highlight the importance of hypokalemia correction in the diagnosis of primary aldosteronism (PA), which is not emphasized sufficiently in the literature or clinical guidelines. Methods: We report the cases of 4 patients with hypokalemia and hypertension in whom the screening and confirmatory diagnosis of PA was made possible only after potassium level normalization. Results: Cases 1 and 2 were referred for evaluation of hypokalemia and hypertension while cases 3 and 4 were admitted to the hospital for severe generalized weakness and palpitations, respectively. Initial labs for all were remarkable for hypokalemia, with potassium levels of 1.9 to 3.2 mEq/L (normal range: 3.5 to 5.0 mEq/L), relatively low aldosterone of <1.0 to 13.0 ng/dL, and elevated aldosterone-to-renin ratio. Saline infusion tests were performed for cases 1 and 2 when potassium was 3.2 mEq/L with post-test aldosterone levels of 9.0 and 3.0 ng/dL, respectively, suggesting the diagnosis of PA as less likely. After potassium repletion, with potassium levels of 3.7 to 4.8 mEq/L, screening aldosterone levels were 27.0 to 64.0 ng/dL, the aldosterone-to-renin ratios were 34.5 to 128.0, and post-saline infusion test aldosterone levels were 27.0 to 64.0 ng/dL, confirming the diagnosis of PA. Computed tomography scans revealed unilateral adrenal adenomas, adrenal vein sampling confirmed the localization, and successful adrenalectomy was done for all 4 cases. Hypertension and hypokalemia resolved in the first 3 cases and improved in the fourth. Conclusion: Hypokalemia may confound the screening and confirmatory work up of PA due to false-negative results. Potassium normalization is very important for correct diagnosis of PA. Abbreviations: ARR = aldosterone-to-renin ratio; AVS = adrenal venous sampling; CT = computed tomography; PA = primary aldosteronism; SIT = saline infusion test