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Idiopathic hypercalciuria: effects of calcium load test on magnesiuria
1Department of Pediatrics, University Hospital of Valencia, Spain.
Insights
This study classifies pediatric idiopathic hypercalciuria into absorptive, renal, and alimentary types. Urinary cAMP levels were not useful for classification, but magnesiuria differences suggest distinct pathogenic mechanisms.
Area of Science:
- Pediatric Nephrology
- Mineral Metabolism
Background:
- Idiopathic hypercalciuria (IH) is a common metabolic disorder in children, often associated with nephrolithiasis.
- Accurate classification of IH subtypes is crucial for understanding pathogenesis and guiding treatment.
- Previous classification methods have limitations in pediatric populations.
Purpose of the Study:
- To evaluate the utility of an oral calcium load test in classifying pediatric idiopathic hypercalciuria.
- To investigate the role of urinary cyclic adenosine monophosphate (cAMP) and magnesiuria in differentiating IH subtypes.
- To explore potential differences in pathogenic mechanisms among IH classifications in children.
Main Methods:
- Twenty-three children with IH and 7 controls underwent an oral calcium load test.
- Urinary calcium to creatinine ratio (UCa/Cr) was measured before and after calcium loading.
- Urinary cAMP and magnesium excretion (magnesiuria) were analyzed in relation to IH subtypes.
Main Results:
- Children were classified into absorptive (n=5), renal (n=10), and alimentary (n=8) hypercalciuria based on UCa/Cr response to calcium loading.
- Urinary cAMP levels showed no significant differences across groups or compared to controls.
- Magnesiuria did not differ significantly between IH subtypes and controls, but increased post-loading, with a positive correlation to calciuria in absorptive hypercalciuria.
Conclusions:
- The oral calcium load test is a valid method for classifying pediatric idiopathic hypercalciuria.
- Urinary cAMP is not a reliable biomarker for classifying IH subtypes in children.
- Observed differences in magnesiuria suggest distinct pathophysiological pathways in absorptive versus renal/alimentary hypercalciuria.
Abstract:
Twenty-three children with idiopathic hypercalciuria and 7 control children were studied. Patients were classified into three groups according to the response to an oral calcium load. Five children displayed absorptive hypercalciuria (UCa/Cr 0.14 +/- 0.04 mg/mg with poor calcium diet and 0.33 +/- 0.16 after loading, p less than 0.01); 10 were classified renal hypercalciuria (UCa/Cr during the fasting state of 0.28 +/- 0.09 and 0.31 +/- 0.11 after loading) and 8 were classified as alimentary hypercalciuria (UCa/Cr 0.14 +/- 0.07 during the fasting state and 0.15 +/- 0.04 after loading). The urinary cAMP showed no significant differences in any of the three groups compared to the control. Magnesiuria did not show significant differences between the two forms of hypercalciuria and the control; a significant increase was observed after the loading and a positive correlation between magnesiuria and calciuria in the absorptive form. Our study supports the validity of the test for the classification of the different forms of hypercalciuria in children. The urinary cAMP is not a valid approach for classification. The difference observed in the magnesiuria suggests a different pathogenic mechanism between the two types of idiopathic hypercalciuria.