Abstract

Shortly after diagnosis of primary hyperparathyroidism, a patient had serum hyperosmolality, polyuria, isosthenuria, profound potassium depletion, and elevated plasma antidiuretic hormone levels, all consistent with nephrogenic diabetes insipidus. After parathyroidectomy, serum calcium and serum osmolality levels fell concurrently. Profound potassium deficits did not recur.We propose that (1) hypercalcemia produced a concentrating defect and polyuria; (2) renal tubular acidosis and polyuria combined to produce severe potassium depletion; (3) hypokalemia potentiated the nephrogenic diabetes insipidus caused by hypercalcemia; and (4) postoperative disappearance of the diabetes insipidus confirmed its reversible, purely metabolic causes.