PRODUCTION OF PARATHYROID-HORMONE BY A MALIGNANT NONPARATHYROID TUMORIN A HYPERCALCEMIC PATIENT

Few cases exist in which the production and secretion of PTH by malign ant nonparathyroid tumors have been authenticated. A 69-yr-old man dev eloped hypercalcemia complicating a primitive neuroectodermal malignan cy that was widely metastatic. The serum level of intact PTH was marke dly increased by immunoradiometric assay (90-290 ng/L; normal, 10-65 n g/L). The serum level of a PTH-related protein was also increased (19- 20 ngeq/L; normal, <10 ngeq/L). Exploration of the neck and mediastinu m at two operations revealed four normal parathyroid glands. Extracts of the metastatic tumor contained immunoreactive PTH and transcripts o f both the PTH and PTH-related protein genes. Thus, hypercalcemia in t his patient was associated with production of PTH by a nonparathyroid malignancy.