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Early childhood hyperkalemia: variety of pseudohypoaldosteronism
Insights
Children with mineralocorticoid-resistant hyperkalemia show inappropriately low fractional potassium excretion and elevated fractional sodium excretion. This suggests a partial renal tubule unresponsiveness to mineralocorticoids, indicating a milder form of pseudohypoaldosteronism.
Area of Science:
- Pediatric Nephrology
- Endocrinology
- Renal Physiology
Background:
- Mineralocorticoid resistance causes hyperkalemia in infants.
- Understanding the underlying mechanisms is crucial for diagnosis and management.
- Early-onset hyperkalemia necessitates investigation into renal electrolyte handling.
Purpose of the Study:
- To investigate electrolyte excretion, renal acidification, and the renin-aldosterone system in infants with mineralocorticoid-resistant hyperkalemia.
- To differentiate this condition from classic pseudohypoaldosteronism and early childhood renal acidosis.
Main Methods:
- Studied fractional electrolyte excretion (potassium and sodium) in 5 non-azotemic infants.
- Assessed renal acidification capacity via acid loading tests.
- Measured plasma aldosterone and plasma renin activity.
Main Results:
- Patients had inappropriately low fractional potassium excretion and significantly increased fractional sodium excretion compared to controls.
- Renal acidification capacity was normal.
- Elevated plasma aldosterone, plasma renin activity, and aldosterone/potassium ratio were observed in patients.
Conclusions:
- Findings support a partial lack of renal tubule response to endogenous mineralocorticoids.
- This condition represents a less severe form of pseudohypoaldosteronism compared to classic forms.
Abstract:
Fractional excretion of electrolytes, renal acidification capacity and the renin-aldosterone system have been studied in 5 non-azotemic children, 19-25 months old, with mineralocorticoid resistant hyperkalemia, discovered in the first month of life. Although fractional potassium excretion was similar in patients and in a group of control healthy children (13.8 +/- 5.2% vs. 8.7 +/- 6.4%) it was inappropriately low in the patients for their higher potassium concentration. Fractional sodium excretion was significantly increased in the patients (1.6 +/- 0.3% vs. 0.67 +/- 0.4, p less than 0.02). Normal net acid and ammonium excretion and intact ability to lower urinary pH during acid loading were observed in all patients. Mean values for plasma aldosterone (37.0 +/- 9.1 vs. 13.9 +/- 11.2 ng/dl), plasma renin activity (12.5 +/- 3.9 vs. 8 +/- 2.8 ng/ml/h) and plasma aldosterone/plasma potassium ratio (7.11 +/- 1.5 vs. 3.08 +/- 1.7) were higher in the patients than in the control subjects (all p less than 0.001). These data support the hypothesis that a partial lack of response of the renal tubule to endogenous mineralocorticoids was present in the patients. This type of pseudohypoaldosteronism is less severe than that described for the classic form and for early childhood renal acidosis.