RELATIONSHIP BETWEEN DISEASE-ACTIVITY AND SERUM LEVELS OF VITAMIN-D METABOLITES AND PTH IN RHEUMATOID-ARTHRITIS

In several studies on patients with rheumatoid arthritis, an associati on of bone loss with a persistently high disease activity has been fou nd. The aim of our study was to investigate the relation between disea se activity and serum levels of vitamin D metabolites, parathyroid hor mone (PTH), and parameters of bone turnover in patients with rheumatoi d arthritis. A total of 96 patients (83 women and 13 men) were divided into three groups according to disease activity measured by serum lev els of C-reactive protein (CRP). In the whole group, serum levels of 1 ,25-dihydroxyvitamin D3 (1,25(OH)(2)D-3) (P < 0.001) and PTH (P < 0.05 ) were negatively correlated to disease activity. The urinary excretio n of collagen crosslinks-pyridinoline (Pyd) (P < 0.001) and deoxypyrid inoline (Dpd) (P < 0.05)-showed a positive correlation with disease ac tivity. The inverse correlation between serum 1,25(OH)(2)D-3 and disea se activity was separately evident in patients with (P < 0.001) and wi thout (P < 0.01) glucocorticoid treatment, in pre-(P < 0.01) and postm enopausal (P < 0.001) women, and in men (P < 0.01). 1,25(OH)(2)D-3 and PTH serum levels were positively correlated to serum bone alkaline ph osphatase (ALP) (P < 0.01). The results indicate that high disease act ivity in patients with rheumatoid arthritis is associated with an alte ration in vitamin D metabolism and increased bone resorption. The decr ease of 1,25(OH)(2)D-3 levels in these patients may contribute to a ne gative calcium balance and inhibition of bone formation. Furthermore, low levels of 1,25(OH)(2)D-3 as an endogenous immunomodulator suppress ing activated T cells and the proliferation of cells may accelerate th e arthritic process in rheumatoid arthritis.