Total and nephrogenous urinary cyclic AMP (cAMP), serum Parathyroid Hormone (PTH) and ionized calcium (Ca) levels were determined in 8 normal subjects, and 16 normocalcemic and 9 hypercalcemic patients with lung cancer. Total and nephrogeneous cAMP levels were significantly increased in both normocalcemic and hypercalcemic lung cancer patients, as compared to normal subjects. There was no significant correlation between serum PTH and total or nephrogenous cAMP in the cancer group. The factors responsible for the elevated nephrogenous cAMP in the lung cancer patients are not known.
We evaluated nephrogenous cyclic adenosine monophosphate ( NcAMP ) levels in 61 normocalcemic patients with documented cancer of various organs and cell types. NcAMP levels were elevated in 17 (28%) and decreased in 13 (21%) of the cancer patients. Both high and low NcAMP levels were seen within the various cancer groups. There was a significant correlation (r = 0.383, P less than 0.01) between NcAMP and serum parathyroid hormone (PTH) levels, suggesting that tumor-related factors affecting NcAMP , may be partially related to native PTH. Alternatively, these factors might be altering the effect of endogenous PTH on renal tubules. A significant negative correlation was also observed between NcAMP and tubular maximum for phosphate (r = -0.356, P less than 0.02) suggesting that either cAMP per se or factors affecting NcAMP alter phosphate excretion. Follow up serum calcium data was available on 48 of the 61 patients. Subsequent hypercalcemia developed independent of the initial nephrogenous cAMP levels. It therefore appears that NcAMP elevation and development of hypercalcemia are two separate paraneoplastic phenomena.
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