Inappropriately elevated concentrations of 1,25(OH)2 vitamin D in serum appear to be responsible for excessive gastrointestinal absorption of dietary calcium in patients with absorptive hypercalcluria. We have examined serum 1,25(OH)2 vitamin D concentrations in another group of children with hypercalciuria in whom urinary calcium excretion was excessive after an overnight fast. Eleven children with idiopathic fasting hypercalciuria (IH) (urinary calcium excretion >4 mg/kg/24 hr and fasting urinary calcium/urinary creatinine ratio >0.21) and seven healthy children were observed while they were eating a diet containing 1 gm calcium per day. Fasting serum 1,25(OH)2 vitamin D concentrations were elevated in children with IH compared with control values (35.3±3.2 vs 21±2 pg/ml, P=0.003), whereas fasting serum parathyroid hormone, 25-OH vitamin D, phosphorus, and ionized calcium concentrations were similar in the two groups. These data suggest that disordered 1,25(OH)2 vitamin D metabolism occurs in children with fasting IH. Absorptive and fasting IH may represent a spectrum of a single disorder characterized by excessive urinary calcium excretion and inappropriately elevated serum concentrations of 1,25(OH)2 vitamin D.
ASJC Scopus subject areas
- Pediatrics, Perinatology, and Child Health