Effects of weight and glucose ingestion on urinary calcium and phosphate excretion: implications for calcium urolithiasis.
Renal handling of phosphate and calcium was studied in 17 hypercalciuric stone-formers, 6 normocalciuric stone-formers and 10 normal subjects before (fasting state) and 45 and 75 min after the ingestion of 100 g glucose. The ratio of fasting urinary calcium to creatinine (UCa/creat) was higher in hypercalciuric than in normocalciuric stone-formers or controls. A positive correlation was found between weight index and fasting UCa/creat for all subjects studied (r = 0.36; P less than 0.05). A negative correlation was apparent between the weight index and the fasting renal threshold phosphate concentration (TmP/GFR) (r = 0.40; P less than 0.02), the latter parameter being slightly but insignificantly lower in hypercalciuric stone-formers than in controls. After glucose ingestion. UCa/creat rose significantly in all groups. The maximal rise in UCa/creat was also positively correlated with the weight index for all patients ( r = 0.42; P less than 0.02), and 75 min after glucose ingestion, TmP/GFR decreased in all groups, dropping to a significantly lower level in the hypercalciuric patients than in the controls. No correlation was apparent between the weight index and the magnitude of the reduction in TmP/GFR. Plasma 1, 25-dihydroxyvitamin D3 and immunoreactive parathyroid hormone were measured before glucose ingestion and were not correlated either with each other or with plasma phosphorus, TmP/GFR, or UCa/creat before or after glucose ingestion. These results imply that weight is a determining factor in the renal handling of calcium and phosphorus. Such findings might be of importance to the clinical investigation and management of calcium stone-formers.
D000328:Adult; D001786:Blood Glucose / Q000032:analysis; D001835:Body Weight; D002118:Calcium / Q000652:urine*; D003404:Creatinine / Q000652:urine; D005260:Female; D005502:Food; D005919:Glomerular Filtration Rate / Q000187:drug effects; D005947:Glucose / Q000494:pharmacology*; D006801:Humans; D007669:Kidney Calculi / Q000652:urine*; D008297:Male; D010710:Phosphates / Q000652:urine*
D001786:Blood Glucose; D010710:Phosphates; D003404:Creatinine; D005947:Glucose; D002118:Calcium