Persistent anemia and hypoalbuminemia in rheumatoid arthritis patients with low serum triiodothyronine level复制标题

低血清三碘甲状腺原氨酸水平的类风湿关节炎患者的持续性贫血和低白蛋白血症

Serum triiodothyronine (T3) levels can be decreased in patients with chronic inflammatory conditions, and this finding is called ‘low-T3 syndrome’ or ‘euthyroid sick syndrome’. Generally, T3 is produced by transformation from thyroxine (T4) under normal homeostatic conditions. In low-T3 syndrome, the thyroid gland is normal, but T3 production by conversion from T4 is decreased secondary to suppression of thyrotropin-releasing hormone (TRH) and thyroid-stimulating hormone (TSH) in the presence of inflammation. Rheumatoid arthritis (RA) is an inflammatory disease characterized by joint destruction and physical dysfunction. Serum free T3 (fT3) levels can be decreased in patients with RA, and inflammatory cytokines such as tumor necrosis factor (TNF) or interleukin (IL)-6, key molecules in the pathogenesis of RA, also play important roles in low T3 syndrome. For example, TNF and IL-6 inhibit the conversion of T4 to T3 and inactivate T3. These findings suggest that RA disease activity and serum fT3 levels are closely linked via inflammatory cytokines such as TNF and IL-6. Low serum T3 levels are reported in 7%–52% of RA patients. One of the reasons for the wide-range of frequencies in low-T3 RA patients may be an incomplete definition of ‘low-T3 patients.’ For example, patients with low-T3 caused by autoimmune thyroid diseases (ATD) or those who are taking anti-thyroid medications were included in previous analyses. Furthermore, because of advances in RA treatment, the clinical characteristics of RA patients may have changed. Therefore, the prevalence and characteristics of RA patients with low-T3 levels have not been fully addressed. In this study, we examined fT3, free T4 (fT4), and TSH levels in RA patients. After excluding patients with ATD or those taking anti-thyroid medications, we analyzed the clinical characteristics of RA patients with low-fT3 levels. We also followed patients with low-fT3 levels and compared the clinical characteristics of patients whose fT3 levels normalized with those who showed persistently low-fT3 levels.

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