[Evidence for a glucose-dependent renal phosphorus leak in normo- and hypercalciuric stone-formers (author's transl)]

Changes in phosphatemia and in maximum renal threshold phosphate concentration (TmP/GFR) have been measured before and 45 and 75 min after oral ingestion of 75 g of glucose in 10 hypercalciuric lithiasic patients (HCI), 8 normocalciuric lithiasic patients (NCI) and 7 control subjects. After glucose ingestion, whereas plasma phosphorus decreased in all 3 groups, TmP/GFR decreased significantly in HCI and NCI but not in controls. A slight increase in calcium excretion was noted in the subjects with HCI and NCI after glucose load. Plasma concentration of 1,25(OH)2D was measured in 8 HCI and 7 controls before and after glucose: there was a significant increase in HCI 45 min after glucose and no modification in control subjects. These results show that a glucose load causes a decrease in TmP/GFR in lithiasic subjects. The results demonstrate the existence in lithiasic patients of perturbations of renal handling of phosphates which could, at least in part, be related to glucose metabolism. This trouble could contribute to the elevation of the serum 1,25(OH)2D observed in these patients.