RENAL REGULATION OF PHOSPHORUS EXCRETION*

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Abstract
Four male patients with apparently normal phosphorus metabolism and renal function were studied during a metabolic balance regimen and then given oral phosphorus supplements. In all cases there was an increase in the level of serum phosphorus, filtered phosphorus and urinary phosphorus. By the end of second 24-hour period, phosphorus excretion had become stabilized. Similar, but opposite responses followed withdrawal of the phosphorus supplements. Tubular response significantly affected phosphorus excretion in less than half of the studies, and in only 1 patient did it assume the major regulatory function. In several instances there were pronounced changes in the filtration rate; the tubular reabsorption, as a derived function, was more closely related to this change than to the variation in phosphorus intake. The parathyroid hormone appears to regulate renal function in response to sustained rather than transient variations in the dietary phosphorus load.