ORIGINAL ARTICLE
The effect of methotrexate on bone metabolism markers in patients with rheumatoid arthritis

Authors
Eiji Torikai¹, Yasunori Kageyama¹, Masaaki Takahashi¹ and Akira Nagano¹

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Received: April 3, 2006 Accepted: August 1, 2006

Abstract
The aim of the present study was to evaluate the influence on urinary excretion levels of N-telopeptide of type I collagen (NTX) and deoxypyridinoline (DPD) as a useful marker for bone resorption, and on serum-bone alkaline phosphate (BAP) levels as a useful marker for bone formation and an early marker of osteoblast differentiation in patients with rheumatoid arthritis (RA) treated with methotrexate (MTX). Thirty patients with RA, diagnosed according to the criteria of the American College of Rheumatology,
were involved in this study between March 2003 and January 2005. None of the patients had a history of hormone (estrogen) replacement therapy. All patients were treated with MTX. Methotrexate was administered perorally at a dosage of 4-10 mg/week. All patients underwent general and physical examinations and routine blood and urinary analysis at the baseline, 3 months and 6 months after the initial treatment. Then the levels of NTX and DPD in urine and BAP in serum were measured in all patients. For comparison with the effect of other DMARDs on bone metabolism markers in RA patients, we measured the levels of NTX and DPD in urine and BAP in serum of RA patients, 13 patients treated with salazosulfapyridine (SASP), and 14 patients treated with actarit (ACT). In patients treated with MTX, NTX levels decreased significantly at 3 months after the initial treatment and remained low at 6 months after the initial treatment, and DPD levels significantly decreased at 6 months after the initial treatment. The mean serum BAP levels changed without significant differences from the baseline at 3 months and 6 months. In patients treated with SASP and ACT, all bone metabolism markers had not changed significantly at the three time points. On disease activity erythrocyte sedimentation rate, C-reactive protein, the number of swollen joints and tender joints, and mHAQ score decreased significantly at 3 months after the initial treatment, and remained at low levels at 6 months after the initial treatment with MTX. Methotrexate therapy looks promising in inhibiting generalized bone loss in patients with RA. In addition, NTX is a more sensitive marker than DPD.

Key words
Bone metabolism marker, Methotrexate (MTX), Rheumatoid arthritis