Renal tubular function in children and adolescents with Gitelnian's syndrome, the hypocalciuric variant of Bartter's syndrome

Renal tubular function was studied in 14 patients with Gitelman'ssyndrome and 14 control subjects. Apart from the biochemicalhallmarks of Gitelman's syndrome, namely alkalaemia, hyperbicarbonataemia, hypokalaemia, hypomagnesaemia (with increasedmagnesium over creatinine ratio), increased urinary chlorideover creatinine ratio, and low urinary calcium over creatinine,the patients were found to have hyperproteinaemia, hypochloraemia,high total plasma calcium concentration, reduced plasma ionizedcalcium concentration, and high urinary sodium excretion. Astatistically significant negative linear relationship betweenplasma magnesium concentration and magnesium excretion correctedfor glomerular filtration was observed in patients. The fractionalcalcium clearance and the urinary excretion of calcium correctedfor glomerular filtration was significantly decreased in patients.In patients the urin ary osmolality after overnight water deprivationranged from 526 to 1067 mmol/kg. Glucosuria and aminoacid uriawere similar in patients and controls. The results of the studydemonstrate the renal origin of hypomag nesaemia and hypocalciuriain Gitelman's syndrome. The failure to demonstrate hyperaminoaciduria,hyperglucosuria, hyperphosphaturia, hyperuricosuria, and severelyimpaired urinary concentrating ability provide evidence fora defect residing in the distal convoluted tubule.