Plasma osteocalcin levels in stone disease. A potential aid in the differential diagnosis of calcium nephrolithiasis.

Plasma osteocalcin levels were measured by radioimmunoassay in 70 consecutive patients with recurrent calcium (sterile) nephrolithiasis during diagnostic evaluation for the cause of the disease. Nephrogenous cyclic adenosine 3,5'-monophosphate levels also were measured in most of the subjects. Included in the sampling, as determined by standard diagnostic criteria, were 12 patients with absorptive hypercalciuria type I, 15 with absorptive hypercalciuria type II, 22 with renal leak hypercalciuria, 11 with normocalciuria, 6 with primary hyperparathyroidism, 3 with renal tubular acidosis and 1 with Paget's disease, as well as 12 control subjects. The observed plasma osteocalcin levels (ng. per ml. mean +/- standard error) were absorptive hypercalciuria I 2.6 +/- 0.20, absorptive hypercalciuria II 3.1 +/- 0.21, renal hypercalciuria 8.7 +/- 0.45, normocalciuric nephrolithiasis 3.3 +/- 0.25, primary hyperparathyroidism 13.2 +/- 0.91, renal tubular acidosis (range) 5.2 to 10.6, Paget's disease 18.0 and control 3.1 +/- 0.20. There were significant differences between the plasma osteocalcin levels of renal hypercalciuria versus primary hyperparathyroidism and renal hypercalciuria/primary hyperparathyroidism versus any other group. There was good correlation between plasma osteocalcin and cyclic adenosine 3,5'-monophosphate data (correlation coefficient 0.72, p less than 0.005). Plasma osteocalcin levels are a potential differential diagnostic tool for patients with stone disease. The diagnostic value compares favorably with that of cyclic adenosine 3,5'-monophosphate, with the advantage that the determination of plasma osteocalcin requires only a single test.