Methotrexate is associated with decreased total thyroxine in patients with rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease characterized by joint swelling, pain, and deformation. RA patients have an increased risk of thyroid dysfunction, and drugs of RA treatment may have potential effects on thyroid function.

This is a single-center cross-sectional study including 281 inpatients with RA in the First Affiliated Hospital of Guangzhou University of Chinese Medicine. The purpose of this study is to explore the correlation between RA therapeutic drugs and thyroid function. The medical records of 281 inpatients with RA were collected, including general data, laboratory examination, complications, and RA treatment. Spearman correlation analysis was used to explore the association of independent variables with thyroid function and antibodies in RA patients. Multinomial logistics and binary logistic regression were used for multivariate analysis. The statistically significance level was set as P < 0.05. SPSS 22.0 was used for statistical analysis.

Patients taking methotrexate (OR = 0.067, 95%CI: 0.008-0.588, P = 0.015) had lower levels of total thyroxine (TT4) (TT4 < 78.38 nmol/L). There was a negative correlation between glucocorticoids (r = - 0.153, P = 0.010) and total triiodothyronine (TT3) level (TT3 ≥ 1.34 nmol/L), but it was not significant in the multivariate regression model of TT3, although the regression model was statistically significant (P = 0.001).

Methotrexate is associated with decreased TT4 levels in RA patients, and glucocorticoids is associated with decreased TT3 levels. Drugs of RA treatment may affect the thyroid function of patients while treating RA, which may be one of the causes of secondary thyroid diseases in RA patients.