Persistent hypercalciuria and elevated 25-hydroxyvitamin D3 in children with infantile hypercalcaemia
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The aim of the study was to characterize abnormalities of calcium-phosphate and vitamin D3 metabolism in children with a past history of “mild” Lightwood-type idiopathic infantile hypercalcaemia. Seventeen seemingly healthy children aged 2 – 12 years, with long-term idiopathic hypercalcaemic syndrome since infancy were studied. Two reference groups were also included (vitamin D3 intoxication/healthy and Williams groups). Despite a long-term milk-restricted diet and a restricted vitamin D3 intake, urinary calcium excretion in the study group was 0.117±0.07 mmol/kg per 24 h. Compared with the reference groups (0.047±0.029 and 0.067±0.06 mmol/kg per 24 h, P<0.05), there was significant hypercalciuria in the children with idiopathic hypercalcaemia since infancy. Serum concentrations of 25-hydroxyvitamin D3 in the study group were also elevated compared with the reference groups (57.4±15.5 vs. 34.6±9.3 and 22.7±10.5 ng/ml). 1,25-Dihydroxyvitamin D3 levels were at the upper limit of normal (45.9±13.1 vs. 35.0±8.1 and 30.0±13.7 pg/ml). Non-progressive, clinically silent nephrocalcinosis was visible on ultrasound examinations. The disturbances of vitamin D3 and calcium-phosphate metabolism persistent in the normocalcaemic phase of idiopathic infantile hypercalcaemia may be a primary metabolic defect of the condition. The mechanisms leading to elevation of metabolites of 1,25-dihydroxy- and 25-hydroxyvitamin D3 and the relationship between this and persistent hypercalciuria and nephrocalcinosis need pathophysiological explanation.
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