Fasting gastrinemia and elevated supersaturation with hydroxyapatite of fasting urine--observations in renal calcium stone patients and controls.

We evaluated serum gastrin, acid-base status, variables of mineral metabolism in fasting blood, as well as pH, relative supersaturation of stone forming constituents, and crystalluria in the associated fasting urine, of control subjects (n = 12), and in age- and weight-matched male normocalciuric (n = 12) and hypercalciuric (n = 12) patients with idiopathic recurrent calcium urolithiasis (RCU). In RCU, mineral metabolism and acid-base data are unchanged, whereas mean serum gastrin is only insignificantly higher as compared to controls. Subclassification of all participants into categories with either high-normal or low-normal gastrin reveals that in RCU with low-normal gastrin there is a higher-than-normal urinary pH and significantly elevated supersaturation of urine with hydroxyapatite. Crystalluria and stone analysis support the assumption that the physico-chemical environment accompanied by low gastrin levels predisposes to urinary precipitation of calcium phosphate with subsequent formation of a stone nidus. pH in fasting urine and integrated fasting serum gastrin correlate significantly, suggesting that low fasting serum gastrin in RCU patients may be considered a risk factor for calcium phosphate stone formation.