Bone metabolism in rheumatoid arthritis; relation to disease activity.

Biochemical parameters of bone metabolism were investigated in 105 ambulant, non-steroid treated patients with RA and compared with parameters of disease activity. Urinary calcium (Ca) and hydroxyproline (OHP) excretions, as parameters of bone resorption and serum alkaline phosphatase (AP), as a parameter of bone formation, were positively related to parameters of disease activity. Serum osteocalcin, another parameter of bone formation, was not related to parameters of disease activity. Patients with active disease (ESR > or = 28 mm and Ritchie articular index > or = 8) had a significant higher urinary Ca and OHP excretion (62 and 42% higher, respectively) than patients with inactive disease. Serum AP and OC were slightly higher (19 and 16%, respectively) in patients with active disease. These results suggest that in RA patients bone metabolism is related to disease activity. In active disease bone resorption seems to be increased more than bone formation, suggesting that prolonged disease activity may contribute to generalized and/or localized osteopenia.