Hypercalcemia and urinary excretion of cyclic AMP in bronchogenic carcinoma

Plasma calcium and phosphate levels and the cyclic AMP/creatinine ratio in the urine were studied in 23 patients with bronchogenic carcinoma. Hypercalcemia was found in 4 patients (17.4%), confirming the frequency of this abnormality observed by others. However, only one patient had both hypercalcemia and hypophosphatemia. In 4 patients with hypercalcemia and no bone metastases, surgical removal of the tumor was followed by return of the plasma calcium level to normal, suggesting that the hypercalcemia was caused by ectopic secretion of a parathormone-like substance by the neoplasm. Contrary to what might be expected, the urinary cAMP/Cr ratio was abnormally low in most patients, including 3 of the 4 patients with hypercalcemia. Moreover, the cAMP/Cr ratio in the urine did not decrease after removal of the tumor. This finding suggests another difference between PTH-like substances of neoplastic origin and natural PTH if, indeed, a PTH-like substance was responsible for the hypercalcemia. © 1977 Société Internationale de Chirurgie.