Changes in renal concentrating ability produced by parathyroid extract.

Polyuria is a frequent symptom of hyperparathyroidism. Impairment of renal concentrating ability, often out of proportion to other signs of renal insufficiency, has been noted in patients with hyperparathyroidism (1-3) as well as in patients and animals with hypercalcemia due to other causes (4-6). In many patients with hyperparathyroidism, extensive deposits of calcium in the renal parenchyma, secondary fibrosis, superimposed pyelonephritis and vascular disease have combined to destroy considerable amounts of renal substance. The mechanism of the reported decrease in renal concentrating ability in such patients is not clear, since fixation of urinary specific gravity is a well-known accompaniment of the simple ablation of renal tissue (7). In the present experiments, renal concentrating capacity was found to be depressed in dogs in which hypercalcemia had been induced for only 24 hours by injecting parathyroid extract. This functional defect was associated with morphologic changes in the distal portions of nephrons and the collecting ducts.