Hypercalcemia in a patient with renal cell carcinoma producing parathyroid hormone-related protein and interleukin-6.

A patient with renal cell carcinoma who developed humoral hypercalcemia of malignancy is reported. A 52-year-old male patient was diagnosed with renal cell carcinoma and multiple lung metastases. A cell line isolated from the surgical specimen exhibited continuous production of parathyroid hormone-related protein (PTHrP) in vitro. The production of PTHrP from the cancer cells was confirmed by RT-PCR and immunoradiometric assay. The serum calcium level was not enhanced, whereas the lung lesion was developing and producing interleukin-6, a possible modulator of osteoclastic resorption. Hypercalcemia was induced when the PTHrP concentration increased up to 3.3 pmol/L.