MODIFICATIONS OF BIOCHEMICAL MARKERS OF BONE AND COLLAGEN TURNOVER DURING CORTICOSTEROID-THERAPY

Serum bone Gla protein (BGP), carboxyterminal cross-linked telopeptide of type I collagen (ICTP) and aminoterminal propeptide of type III pr ocollagen (PIIINP) levels were determined in 8 patients with autoimmun e disorders (2 with systemic lupus erythematosus, 3 with rheumatoid ar thritis, 2 with Sjogren's syndrome and 1 with mixed connective tissue disease) before and after 1, 2 and 4 months of treatment with oral pre dnisone (at a dosage of 1 mg/kg bw/day, p.o. during the first month, t hen reduced to 0.1-0.2 mg/kg bw/day), Before treatment, mean serum BGP (mean+/-SE: 5.3+/-0.4 ng/ml) and ICTP (2.8+/-0.2 ng/ml) levels were s imilar to those recorded in an age and sex matched control group (n=40 : 5.4+/-0.1 ng/ml and 4.1+/-0.3 ng/ml, respectively), On the other han d, serum PIIINP levels (2.2+/-0.3 ng/ml) were significantly (p<0.008) lower than those found in controls (3.3+/-0.2 ng/ml). During glucocort icoid therapy, serum BGP levels significantly decreased after 1 month (2.9+/-0.4 ng/ml; p<0.001), but returned to baseline values after 2 an d 4 months of treatment (4.7+/-0.4 ng/ml and 5.3+/-0.3 ng/ml, respecti vely), On the contrary, no significant changes were observed in serum ICTP levels during treatment (1st month: 2.7+/-0.4 ng/ml; 2nd month: 3 .0+/-0.4 ng/ml; 4th month: 2.4+/-0.3 ng/ml), Serum PIIINP mean concent ration significantly decreased after 1 (1.6+/-0.3 ng/ml; p<0.004) and 2 months of glucocorticoid administration (1.5+/-0.2 ng/ml; p<0.01); a fter 4 months, serum PIIINP levels were again reduced as before therap y (1.8+/-0.2 ng/ml). In conclusion, our study shows the presence of no rmal bone turnover indexes and of altered collagen synthesis in patien ts with autoimmune disorders, The use of high doses of oral steroids i s associated with a prompt decrease of bone formation and collagen syn thesis, without any significant changes in bone resorption; however, t he negative effects on bone formation and collagen synthesis seem to r evert after lowering corticosteroid dosage, Serial determinations of t he markers of bone and collagen turnover are able to give useful and r eliable information on the peripheral effects of steroids excess.