Serial Changes in Serum Calcium and Phosphorus Concentration and in Urinary Phosphorus Excretion after Parathyroid Surgery: Further Evidence for a Dual Effect of Parathyroid Hormone

Abstract

Determinations of serum calcium and phosphorus concentrations, 24-hour urinary phosphorus excretion, and phosphorus and creatinine clearances were performed serially before and following corrective surgery in 8 patients with primary hyperpara thyroidism. Similar studies were carried out in a euparathyroid patient following inadvertent total parathyroidectomy. Thus the effects of an acute change in both elevated and normal levels of endogenous parathyroid hormone could be studied. An immediate reduction in urinary phosphorus excretion and a return of the elevated serum calcium concentration to normal, without a concomitant elevation in the serum phosphorus level or a consistent alteration in the glomerular filtration rate, followed the removal of a functioning parathyroid adenoma in each hyperparathyroid patient. These changes, correlated with a similar sequence of events in the euparathyroid patient subjected to total parathyroidectomy, are unequivocal evidence for a direct phosphaturic action of endogenous parathyroid hormone on the renal tubules of man. The postoperative decline in serum calcium content coincident with the reduction in phosphate excretion in both euparathyroid and hyperparathyroid subjects is further evidence for the duality of this action and an indication that both major actions are simultaneous. From 2 to 10 days were required postoperatively in the hyperparathyroid patients before serum phosphorus levels rose into the normal range, despite the reduction in phosphate excretion. The delayed postoperative return of serum phosphorus levels to normal in these patients without concomitant hypocalcemia is consistent with a depletion of extraskeletal phosphorus produced by the chronic excess of parathyroid hormone with or without alterations in the distribution of inorganic phosphorus between extraskeletal reservoirs and the bones. The similar sequence of events in the euparathyroid subject, differing primarily in duration, is also consistent with an effect of parathyroid hormone on the intracellular concentration of phosphorus in normal man.