Cancer-Associated Hypercalcemia

To the Editor: The study by Stewart and his co-workers¹ is a thorough and scholarly evaluation of patients with cancer-associated hypercalcemia. An understanding of the cause of the hypercalcemia is obviously of critical importance. However, certain data describing the blood levels of parathyroid hormone in these patients and in the control and hyperparathyroid patients are confusing; these data leave unanswered the question of whether parathyroid hormone is the humoral agent responsible for the hypercalcemia. The authors report that mean levels of immunoreactive parathyroid hormone in hypercalcemic patients with cancer were lownormal to undetectable in four separate radioimmunoassays that detect different.