ECTOPIC PRODUCTION OF INTACT PARATHYROID-HORMONE BY A SQUAMOUS-CELL LUNG-CARCINOMA IN-VIVO AND IN-VITRO

Ectopic tumoral production of intact parathyroid hormone (PTH) is rare . The PTH-related protein is the common cause of hypercalcemia in most solid tumors, particularly squamous and renal carcinomas. We report t he case of a 71-yr-old man with a PTH-producing squamous cell lung car cinoma. Immunocytochemical analysis of the tumor tissue as well as of cultured tumor cells revealed PTH positive staining. Cultured tumor ce lls released PTH and were calcium sensitive, producing 122 +/- 16 pg/m u g DNA of intact PTH (mean +/- SEM) at 0.5 mmol/L calcium compared wi th 26 +/- 2 pg/mu g DNA at 3.0 mmol/L calcium. Somatostatin analogues have been used in the treatment of humoral hypercalcemia of malignancy (HHM). However, we found that somatostatin (0.1 mu g/L) in cultured t umor cells increased the release of intact PTH (123 +/- 19 versus 82 /- 1 pg/mu g DNA, P < 0.05) and thus might have a negative effect on t he HHM. This report is the first to describe a true ectopic PTH-produc ing squamous cell lung carcinoma associated with HHM.