title: Basal parathyroid activity and renal calcium handling during an intravenous calcium load.
abstract: Urinary excretion of calcium and urinary cyclic AMP (cAMP), plasma parathyroid hormone (PTH) and ionized serum calcium concentration, and creatinine clearance were measured in 15 healthy humans. In the same subjects, renal tubular reabsorption of calcium was evaluated by analyzing the regression line of urinary calcium excretion rate on rising the level of serum calcium during an intravenous calcium infusion. The regression line intercept on the y-axis, which has been proposed to depend on the calcium reabsorption in the renal distal tubule, was found to be significantly related to both urinary cAMP and PTH levels. The theoretical renal threshold for calcium excretion was directly related to the y-axis intercept and thus also to the index of parathyroid activity. No relationship was found between urinary cAMP or plasma PTH levels and the regression line slope of urinary calcium to serum calcium. In healthy subjects, parathyroid activity significantly affects the extrapolated regression line of urinary calcium to serum calcium by changing the intercept, but not the slope.
mesh_terms: D000328:Adult; D002118:Calcium / Q000008:administration & dosage / Q000652:urine*; D000242:Cyclic AMP / Q000652:urine; D006801:Humans; D007263:Infusions, Parenteral; D007668:Kidney / Q000378:metabolism*; D007677:Kidney Function Tests; D008297:Male; D010281:Parathyroid Hormone / Q000652:urine*; D013960:Thyroid Function Tests
chemical_list: D010281:Parathyroid Hormone; D000242:Cyclic AMP; D002118:Calcium