Relationship between bone mineral density and urine level of NTx in rheumatoid arthritis

We analyzed the relationship between the level of type-I collagen N-telopeptide (NTx) in urine (U-NTx) and bone mineral density (BMD) in patients with rheumatoid arthritis (RA). The subjects were 62 female patients with RA who had experienced the menopause 5 years or more before the study commenced, and who had not been treated for osteoporosis. The mean age of the subjects was 61.6 years and the mean disease duration was 13.3 years. They were classified for global functional status (classes I to IV), and then grouped based on the presence or absence of corticosteroid administration. Bone mineral density (BMD) and U-NTx levels were measured. In the presence of corticosteroid administration (CS group; n = 40), the mean level of U-NTx/creatinine (Cr) was 88.8 nM and the percent young adult mean (%YAM) for BMD was 71.2%. In the no corticosteroid (nCS group; n = 22), the values were 72.1 nM and 78.2%, respectively. The U-NTx/Cr value and %YAM were not significantly different between the CS group and the nCS group. A negative correlation was observed between the U-NTx/Cr value and %YAM in both groups (P = 0.005 and P = 0.0265). No significant difference was observed for the U-NTx/Cr value or %YAM between the CS and nCS groups, in any class. In the CS group, a positive correlation was observed between the U-NTx/Cr value and the total dose of corticosteroid (P = 0.001), and a negative correlation was observed between the %YAM and the total dose of corticosteroid (P = 0.003). These results suggested that preventive medical treatment for osteoporosis is required for RA patients in class III, irrespective of whether they have had corticosteroid administration.