Nephrogenous cyclic AMP and plasma parathyroid hormone in hypercalcaemia: the influence of renal function

Abstract

Immunoreactive parathyroid hormone (PTH) levels and nephrogenous cyclic adenosine monophosphate (cAMP) have been reported to be useful parameters in the diagnosis of hyperparathyroidism. Measurements in hyperparathyroid patients usually give values above the normal range when PTH is measured with a carboxyterminal radioimmunoassay and when nephrogenous cAMP is related to glomerular filtration rate. We tested these two parameters in two groups of hypercalcaemic patients (twelve cases of primary hyperparathyroidism and fourteen cases of hypercalcaemia of non-parathyroid origin) and in two groups of normocalcaemic subjects (twenty-one young healthy volunteers and fourteen elderly subjects without parathyroid disease). Slight impairment of renal function caused elevated values of immunoreactive parathyroid hormone in a carboxyterminal radioimmunoassay and also of nephrogenous cAMP when related to glomerular filtration rate. We found that elevated nephrogenous cAMP without parathyroid disease could be attributed to renal insufficiency and to the mode of expression generally used for the nephrogenous cAMP.

Relative contribution of various expressions of cAMP excretion to other indices of parathyroid function, as tested by discriminant multivariate linear regression analysis.

“…In monovEiriate analysis the classification accuracy of any of the expressions of cAMP excrétion lies between that of calcivim and parathyrin. Our conclusions conceming this last point, however, might not be valid if patients with rénal insufficiency (32), or more patients with malignancy (in whom cAMP excrétion might be influenced by other factors than parathyrin) (21), had been included in this study.…”