BACKGROUND: Hypokalemia due to renal potassium wasting in the absence of 
hypertension, moderate metabolic alkalosis, hyperreninism and hyperaldosteronism 
suggest the presence of Bartter's syndrome. The underlying cause is an inherited 
defect of sodium chloride reabsorption in the thick ascending limb of Henle. A 
differential diagnosis of Bartter's syndrome is Gitelman's syndrome, another 
hypokalemia-hypomagnesemia syndrome, which is thought to be caused by a 
transport defect in the distal tube.
PATIENTS AND METHODS: We report 3 patients presenting with signs primarily 
suggestive of Bartter's syndrome, who turned out to have Gitelman's syndrome 
after determining the excretion of calcium in the urine.
RESULTS: Two women, 36- and 55-year old, suffered from paresthesias in the hands 
and feet and from tetanic convulsions. The brother of the 36-year old woman 
presented in our hospital because of an accidentally discovered hypokalemia 
without any clinical symptoms. In all patients the outstanding biochemical 
features were hypokalemia, hypomagnesemia and moderate metabolic alcalosis. The 
renin and aldosterone values were inappropriately high. The most characteristic 
finding in the urine, besides the presence of hyperkaliuria was the diminution 
of calcium excretion, despite normocalcemia.
CONCLUSION: The association between sodium and calcium reabsorption in the loop 
of Henle predicts hypercalciuria in patients with a defect in salt reabsorption 
in this segment, as in Bartter's syndrome. In Gitelman's syndrome the laboratory 
features resemble the findings in Bartter's syndrome, except for the presence of 
hypocalciuria. Since hypocalciuria follows also the administration of thiazide 
diuretics, which act in the early part of distal tube, a transport defect in 
this part of the tube is thought to be responsible for the electrolyte 
disturbances in Gitelman's syndrome. The measurement of the urinary calcium 
excretion in patients with an unclear hypokalemia-hypomagnesemia-syndrome allows 
easily the differentiation between Bartter's and Gitelman's syndrome.