Bone mineral loss, bone histomorphometry and vitamin D metabolism in patients with rheumatoid arthritis on long-term glucocorticoid treatment.

Long-term glucocorticoid treatment might interfere with the vitamin D metabolism. The serum concentrations of 25-OHD were significantly reduced whereas the circulating levels of 1,25-(OH)2D were normal in 50 patients with rheumatoid arthritis on long-term treatment with small doses of prednisone. The bone mineral content of the forearm was significantly reduced, but the degree of bone loss did not correlate with duration of treatment or dose of prednisone given. Quantitative bone histomorphometry was performed in 18 patients. Apart from a significant correlation between serum 25-OHD and the fractional trabecular bone volume, no relationships were observed between bone histomorphometry and vitamin D metabolites or serum iPTH. The results indicate that the bone loss was due to a decreased osteoblastic activity rather than to an impaired vitamin D metabolism.