[A study of calcium metabolism in calcium-containing stone formers]

To clarify the pathogenesis of calcium-containing urinary stone, calcium metabolism of the 113 patients with calcium-containing stone was studied by fasting and oral calcium loading test. The stone patients were classified into four groups. Those were normocalciuria (NC, n = 60), absorptive hypercalciuria-1 (AH-1, n = 26), absorptive hypercalciuria-2 (AH-2, n = 16) and renal hypercalciuria (RH, n = 11). In the AH-1 group, hypercalciuria resulted from enhancement of intestinal calcium (Ca) absorption. The increase in serum Ca from absorbed Ca increased renal filtered load of Ca. Urinary excretion of Ca was correlated to that of sodium (Na) in fasting and Ca load, and both increments were also correlated in Ca load. As of this fact, the increase in Na excretion was responsible for a cause of hypercalciuria in the AH-1 group. In the RH group, the serum ionized Ca level and % tubular reabsorption of Ca were significantly lower than those of other groups. Urinary excretion of Ca and Na ratio was significantly higher than that of the NC and AH-1 groups. This condition was due to an impaired renal tubular reabsorption of Ca and the resulting secondary hyperparathyroidism. These findings suggested was response disorder of distal tubular to parathyroid hormone. Urinary excretion of phosphorus (P) was correlated to that of Na in fasting and Ca load, and both increments were also correlated in Ca load in the AH-1 group. The increase in urinary excretion of P resulted from the secondary hyperparathyroidism in the RH group.(ABSTRACT TRUNCATED AT 250 WORDS)