Fasting gastrinemia and elevated supersaturation with hydroxyapatite of fasting urine — Observations in renal calcium stone patients and controls

Summary 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 physicochemical 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 rick factor for calcium phosphate stone formation.Abbreviations used in this paper RCU Recurrent calcium urolithiasis - NC Normocalciuria - I-HC Idiopathic hypercalciuria - HAP Hydroxyapatite - cAMP cyclic AMP