[Osteocalcin and bone metabolism in rheumatoid arthritis and osteoarthritis]

Osteocalcin is the most abundant noncollagenous protein of bone and is regarded as the best biochemical marker for bone formation. The synthesis of this protein in osteoblasts is stimulated by 1.25-Dihydroxyvitamin D3 (1.25(OH)2D3). The aim of this study was to examine the rate of bone formation measured by osteocalcin in patients (pts) with rheumatoid arthritis (RA) (n = 58) and osteoarthrosis (OA) (n = 14) and its dependence on various parameters of calcium and phosphate metabolism, especially vitamin D metabolites. Furthermore we compared the significance of alkaline phosphatase and osteocalcin as a parameter for bone turnover in these patients. According to treatment pts with RA were divided into four groups: one receiving gold salts (n = 14), one glucocorticoids (n = 13), one chloroquine (n = 14), and one nonsteroidal antiinflammatory drugs (NSAID) (n = 17). Pts with OA and RA treated with NSAID showed significantly lower values of osteocalcin than pts with RA treated with glucocorticoids or gold. In contrast to osteocalcin, alkaline phosphatase was significantly higher in all pts with RA than in pts with OA. 1.25(OH)2D, which was significantly (p less than 0.05) elevated in pts with RA treated with glucocorticoids, correlated significantly with parathyroid hormone (PTH). These data indicate that bone metabolism, at least in pts with OA and RA treated with NSAID is characterized by a decreased bone formation which is probably compensated in part in pts treated with glucocorticoids, as 1.25(OH)2D and PTH are significantly (p less than 0.05) elevated. Furthermore, the osteocalcin values were closely correlated with 1.25(OH)2D in pts with OA.(ABSTRACT TRUNCATED AT 250 WORDS)