Effect of Parathyroid Extract on Renal Cyclic AMP Excretion in Patients with Normocalciuric Nephrolithiasis

Abstract

It is uncertain whether normocalcemic, normocalciuric patients with calcium nephrolithiasis have a disorder of calcium metabolism. We studied the effect of a parathyroid extract (PTE) infusion (1.4 U/kg body weight) on the urinary cyclic AMP excretion in 16 such patients. For comparison, we investigated groups of normal individuals and patients with primary hyperparatyhroidism, renal insufficiency and different gastrointestinal diseases. The increase of cyclic AMP above basal excretion in patients with nephrolithiasis was only 1.2 ± 0.3 µmol/h (mean ± SEM), versus 2.5 ± 0.5 µmol/h in normal subjects (p < 0.05) although the basal excretion was similar. Patients with renal insufficiency had low basal excretion of cyclic AMP and little stimulation of excretion by PTH (increase, 0.3 ± 0.06 µmol). Patients with primary hyperparathyroidism had high baseline cyclic AMP excretion but subnormal stimulation by PTE (increase, 0.46 ± 0.13); in contrast, patients with different gastrointestinal disease had high baseline excretion and supranormal stimulation of cyclic AMP excretion (increase, 5.2 ± 0.6). We speculate that an impaired response to PTH might be involved in the slightly increased urinary calcium excretion in normocalcemic stone formers suggested by others.

Key words

Urinary Cyclic AMP - Parathyroid Extract - Serum Calcium - Normocalciuric Nephrolithiasis

1 Contains parts of the Thesis of K.G.M. at the University of Bonn, Germany