Die Beziehung zwischen Osteocalcin und der Mineralisationsrate des Skeletts

Summary

Measuring bone turnover by noninvasive methods is rather difficult in osteoporosis. Thus, in patients with osteoporosis the differentiation into “low turnover” and “high turnover” osteoporosis often remains a problem. The protein osteocalcin is thought to be a marker of bone turnover. It was the aim of the present study to investigate the relation between the osteocalcin concentration in serum and the mineralization rate of skeleton derived from tracerkinetic measurements. A total of 55 calcium kinetic investigations were performed in 47 patients suffering from various bone diseases e.g. osteoporosis, Paget’s disease, primary hyperparathyroidism, hypoparathyroidism, and renal osteodystrophy. A trace amount of calcium tagged by 0.2 MBg ⁴⁷Ca was intravenously injected. Subseguently the specific activity of ⁴⁷Ca in serum was measured in blood samples drawn up to 1 week and whole body retention of ⁴⁷Ca employing a total body counter was followed up to 4 weeks after injection. Applying a catenary four compartmental model the accretion rate of calcium in the skeleton was calculated. Osteocalcin in serum was measured by a radioimmuno assay. In patients without renal failure a significant linear correlation was observed between osteocalcin and calcium accretion rate. By contrast, in patients on regular dialysis treatment disproportionally high and low values of osteocalcin were found. These data show the feasibility of osteocalcin as marker of bone formation in patients without renal failure. The influence of other metabolic factors on the relation between osteocalcin and bone turnover still remains to be investigated in more detail.