VARIAZIONI SERIATE DEI LIVELLI PLASMATICI DI CALCIO, FOSFATO E PARATORMONE DURANTE IL TEST DI PAK NEI PAZIENTI CON IPERCALCIURIA E NEI SOGGETTI NORMALI

In 31 hypercalciuric patients and in 14 normal subjects (N) plasma calcium [total (P[ca]) and diffusible (CaUF)] levels, phosphate (pp) and parathyroid hormone, renal threshold phosphate concentration (Tm PO4/GFR), urinary calcium (CaE) and the fraction of filtered calcium excreted (FECa) were measured during an oral calcium load (CL). No differences were found in P[ca] and CaUF, both in the fasting state and after CL, among N and absorptive (IA) and renal (IR) hypercalciuric patients. In all but hyperparathyroid patients P(P) and Tm PO4/GFR rose after CL. CaE and FECa, after CL, were significantly higher in IA and in IR than in N, though the filtered load of calcium was not significantly different. These data show that in absorptive hypercalciuria there is no higher absorptive increase in filtered load of calcium than in normal subjects; they suggest that hypercalciuria is accounted for by a reduced tubular reabsorption of filtered load of Ca.