Nephrogenous cyclic AMP levels in primary hyperparathyroidism.

The clinical utility of urinary cyclic adenosine-3',5'-monophosphate (cAMP) determinations has been limited by the overlap between hyperparathyroid and normal patients. We evaluated the potential of the parathyroid hormone (PTH)-dependent, nephrogenous cAMP in the diagnosis of hyperparathyroidism. Twenty-three patients with primary hyperparathyroidism and 19 control subjects had two-hour urine collections and blood sampling at midpoint. Nephrogenous cAMP level was calculated as total urinary cAMP excretion minus the amount filtered. The total urinary cAMP excretion (micromols per gram of creatinine) was higher in hyperparathyroid patients (6.8 +/- .5 SE), but overlapped with values obtained in controls (2.9 +/- .15). The level of nephrogenous cAMP (percent of total) was also higher in hyperparathyroid patients (72.5 +/- 1.8) than controls (26.3 +/- 4.1) and clearly separated the groups. Determination of nephrogenous cAMP levels may be useful in the diagnosis of hyperparathyroidism.