Test Details: This test is used for evaluation of hypo- or hyperphosphatemic states and evaluation of patients with nephrolithiasis. A variety of factors influence renal tubular phosphate reabsorption and consequent urine excretion. Factors that increase urinary phosphorus excretion include high phosphorus diet, parathyroid hormone, low dietary potassium intake. Factors that are associated with decrease in urinary phosphorus excretion include low dietary phosphorus intake, insulin and decreased intestinal absorption of phosphorus.