Wuthapanich T.Phakdeekitcharoen P.Sevamontree C.Phakdeekitcharoen B.Mahidol University2026-06-222026-06-222026-03-01Journal of Nephrology Vol.39 No.2 (2026) , 307-31711218428https://repository.li.mahidol.ac.th/handle/123456789/117477Background: Hyperkalemia is a lethal condition resulting in cardiac dysrhythmias and death. Identifying the causes of hyperkalemia is crucial for treating and preventing future recurrence. Methods: A prospective cohort study was conducted to evaluate the association between plasma aldosterone level, transtubular potassium gradient, and their ratios in distinguishing the causes of hyperkalemia (serum potassium ≥ 5.8 mmol/L) in the outpatient clinic. Results: Forty-two patients and 26 controls completed the study. The causes of hyperkalemia were classified into three major groups: 1) drug-induced (27 cases), 2) diabetes-related (7 cases), and 3) chronic kidney disease (CKD)-related hyperkalemia (7 cases), and one case of renal tubular acidosis. The mean serum potassium level of the hyperkalemia group was significantly higher than the control group (6.13 ± 0.29 vs 4.27 ± 0.44 mmol/L, P < .001). The mean transtubular potassium gradient values were 3.48 ± 1.87 vs 5.27 ± 1.46, P < .001, respectively. The cut-off aldosterone/transtubular potassium gradient ratio of >2.5 ng/dL or transtubular potassium gradient <5 had comparable sensitivity (64.3% vs 76.2%) and specificity (76.9% vs 53.8%) in discriminating between the hyperkalemia group and the control group, suggesting an inadequate collecting tubule response to hyperkalemia. CKD-related hyperkalemia showed a wide range of transtubular potassium gradients. Lastly, our population was likely to develop diabetes-related hyperkalemia, possibly due to aldosterone resistance from tubular defects. Conclusion: The combined utilization of plasma aldosterone level, transtubular potassium gradient, and their ratios provides a maximum advantage in differentiating causes of hyperkalemia. Additional studies with larger sample sizes and different cut-off serum potassium levels for hyperkalemia are required to further characterize these findings.MedicineArticleSCOPUS10.1093/joneph/aajaf0412-s2.0-1050421235831724605942008517