Hypothyroidism and its Association with Systemic Lupus Erythematosus: A Cross Sectional Study in Chinese Patients

Background: Specific factors correlated with hypothyroidism in systemic lupus erythematosus (SLE) patients remain unclear. Therefore, we aim to evaluate the prevalence of thyroid dysfunction in Chinese patients with SLE and the relationship between clinical hypothyroidism and SLE. Methods: We conducted a cross sectional study of the prevalence of thyroid dysfunction in 672 patients with SLE and 605 age- and sex-matched healthy controls. Demographic, clinical, and biochemical data were compared between 58 patients with SLE with hypothyroidism and 197 patients with SLE with euthyroidism. Multivariate analysis was performed using binomial logistic regression analysis. Spearman's rank correlation was used to identify an association between thyroid function and disease activity. Results: The prevalence of thyroid dysfunction was significantly higher in patients with SLE than in controls (70.7% vs 19.7%). SLE was associated with higher rates of hypothyroidism (9.6%, P <= 0.001) and euthyroid sick syndrome (49.6%, P <= 0.001) compared with control subjects. Further analyses showed that hypothyroidism in patients with SLE was associated with high blood pressure, renal disorder, high serum creatinine, high uric acid, hyperlipidaemia, low C3 and C4, positive anti-dsDNA antibodies, and high SLE disease activity index (SLEDAI) score. In multiple logistic regression models, albumin, platelet count, serum creatinine, and anti-dsDNA antibodies were associated with hypothyroidism. Finally, free tri-iodothyronine was significantly negatively correlated with SLEDAI score. Conclusions: Hypothyroidism was more prevalent in patients with SLE. There was a relationship between hypothyroidism with renal disorder and lupus activity. Albumin, platelet count, serum creatinine, and anti-dsDNA antibodies were correlated with hypothyroidism.