Short-Term Effects of TNF Inhibitors on Bone Turnover Markers and Bone Mineral Density in Rheumatoid Arthritis

TNF alpha inhibitors (TNF alpha I) exert positive effects on disease activity in rheumatoid arthritis (RA). Bone involvement is a major determinant of functional impairment in this disease. Here we investigated the short-term effects of TNF alpha I therapy on bone metabolism and density. We studied 54 patients with RA starting a TNF alpha I biologic drug, in whom any factor known to interfere with bone metabolism was excluded or rigorously accounted for. We measured at baseline and after 6-month therapy bone turnover markers: N-propeptide of type I collagen (P1NP), and bone alkaline phosphates for bone formation and serum C-terminal telopeptide of type I collagen (CTX) for bone resorption. We also evaluated bone mineral density (BMD) at hip and lumbar by dual-energy X-ray absorptiometry. All bone markers rose significantly and these changes were not dependent on steroid dosage. A significant decrease in femoral neck BMD was also observed. These results indicate that TNF alpha I therapy in RA over 6 months is associated with an early increase in bone turnover and a decline in hip BMD.