Acute Myeloblastic Leukemia and Hypercalcemia

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Abstract
We studied a patient with acute myeloblastic leukemia, hypercalcemia, hypophosphatemia and inappropriately elevated serum parathyroid hormone levels to define the mechanism of the hypercalcemia. On six occasions during two years, hypercalcemia occurred in conjunction with relapses of leukemia. Each time, serum calcium decreased to normal levels in parallel with reduction of the leukemic mass. During two periods of hypercalcemia, immunoreactive parathyroid hormone values were abnormally high. In addition, hormone was detected in vitro after short-term incubation of the leukemic cells (after 24 hours, the patient's cells produced 129 pg of PTH per milliliter, whereas myeloblasts from a normocalcemic patient with leukemia produced only 33 pg). In freezethawing experiments, 39 pg of parathyroid hormone was released from 1 X 108 of the patient's myeloblasts; no hormone was released from the normocalcemic cells. These findings suggest that the hypercalcemia resulted from ectopic parathyroid hormone production by leukemic cells. (N Engl J Med 295:692–694, 1976)