Ectopic parathyroid hormone production by a squamous carcinoma of the tonsil.

A patient with recurrent squamous carcinoma of the neck showed hypercalcemia with the immunoreactive parathyroid hormone (PTH) level within the upper limits of normal range, this being inappropriate for the degree of hypercalcemia. An immunoreactive peak of PTH was found in the tumor tissue extract, which appeared on column chromatography to be in the region of elution of pure bovine PTH. The tumor tissue showed positive immunoperoxidase reaction for PTH compared with negative reaction when the patient had normocalcemia. These findings are strong evidence that the tumor produced a PTHlike substance.