Lung cancer associated with hypercalcemia induced by concurrently elevated parathyroid hormone and parathyroid hormone-related protein levels

In general, many cases of malignancy-associated hypercalcemia are due to HHM. In patients with humoral hypercalcemia of malignancy (HHM), it has been reported that plasma parathyroid hormone-related protein (PTHrP) and cyclic adenosine monophosphate (cAMP) levels were elevated, while plasma PTH and active vitamin D(3) levels were suppressed. Our patient showed hypercalcemia with a concurrent increase in plasma and tumor tissue PTHrP and PTH concentrations and also high cAMP and low 1-25(OH)(2)VD(3) levels in the plasma. These data suggest that the hypercalcemia exhibited by our patient was consistent with HHM due to lung cancer and its liver metastasis. Moreover, diagnostic imaging and autopsy findings showed no appreciable lesions of the parathyroid gland. In addition, histopathologic examination of the primary and metastatic tumors revealed the existence of PTH immunohistochemically stained with anti-PTH antibodies, suggesting an ectopic-PTH-producing lung tumor. From these data, our patient was diagnosed with a rare case of lung cancer, which produced both ectopic PTH and PTHrP.