Parameters of evaluation and correlation of renal phosphate handling and of parathyroid function in children.

The aim of the study was to establish normal values for parameters of parathyroid (PT) function in childhood and to examine whether a correlation could be found between these parameters and tubular phosphate (P) reabsorption. Values for PTH (carboxyl terminal) and urinary cAMP (UcAMP) throughout childhood were found to be significantly lower than in adults, with mean values of 0.3 ng/ml (30 pmol/l) and 1.96 nmol/dl glomerular filtrate (GF) respectively. A significant correlation was found between UcAMP and tubular P reabsorption (TP), expressed by the equation: TP = 5.5-(0.5 x UcAMP) mg/dl GF (= 1.78-(0.16 x UcAMP) mmol/dl GF, with a scatter of 10.6 mg/dl around the mean (+/- 1 SD). These data appear to permit the evaluation of primary tubular components in patients with defects of renal P handling, as opposed to those related to PT activity.