Abstract： Objective:To investigate the risk factors of childhood systemic lupus erythematosus (SLE) with thyroid dysfunction and to explore the relationship between thyroid hormone and kidney injury of lupus nephritis (LN).Methods:In this retrospective study, 253 patients who were diagnosed with childhood SLE and hospitalized in the First Affiliated Hospital of Zhengzhou University from January 2019 to January 2021 were enrolled in the case group, and 70 healthy children were the control cases. The patients in the case group were divided into the normal thyroid group and the thyroid dysfunction group. Independent t-test, χ 2 test, and Mann-Whitney U test were used for comparison between the groups, Logistic regression analysis was used for multivariate analysis, and Spearman correlation. Results:A total of 253 patients, there were 44 males and 209 females in the case group, and the age of onset was 14 (12, 16) years; a total of 70 patients, 24 males and 46 females were in the control group, and the age of onset was 13 (10, 13) years. The incidence of thyroid dysfunction in the case group was higher than that in the control group (48.2% (122/253) vs. 8.6% (6/70), χ2=36.03, P<0.05). Of the 131 patients, there were 17 males and 114 females in the normal thyroid group, and the age of onset was 14 (12, 16) years. Of the 122 patients in the thyroid dysfunction group, 28 males and 94 females were in the thyroid dysfunction group, and the age of onset was 14 (12, 16) years. Of the 122 had thyroid dysfunction, including 51 cases (41.8%) with euthyroid sick syndrome, 25 cases (20.5%) with subclinical hypothyroidism, 18 cases (14.8%) patients with sub-hyperthyroidism, 12 cases (9.8%) with hypothyroidism, 10 cases (8.2%) with Hashimoto′s thyroiditis, 4 cases (3.3%) with hyperthyroidism, and 2 cases (1.6%) with Graves disease. Compared to patients with normal thyroid function, the serum level of triglyceride, total cholesterol, urine white blood cell, urine red blood cell, 24 h urine protein, D-dimer, and fibrinogen, ferritin and systemic lupus erythematosus disease activity Index-2000 (SLEDAI-2K) score were higher in patients with thyroid dysfunction ( Z=3.07, 3.07, 2.48, 3.16, 2.40, 3.99, 2.68, 2.55, 2.80, all P<0.05), while the serum level of free thyroxine and C3 were lower in thyroid disfunction patients (10.6 (9.1, 12.7) vs. 11.3 (10.0, 12.9) pmol/L, and 0.46 (0.27, 0.74) vs. 0.57 (0.37, 0.82) g/L, Z=2.18, 2.42, both P<0.05). The higher level of triglyceride and D-dimer were the independent risk factors for childhood SLE with thyroid dysfunction ( OR=1.40 and 1.35, 95% CI 1.03-1.89 and 1.00-1.81, respectively, both P<0.05). There were 161 patients with LN in the case group, all of which were conducted with renal biopsies, including 11 cases (6.8%) with types Ⅰ LN, 11 cases (6.8%) with typesⅡLN, 31 cases (19.3%) with types Ⅲ LN, 92 cases (57.1%) with types Ⅳ LN, and 16 cases (9.9%) with types Ⅴ LN. There were significant differences in the level of free triiodothyronine and thyroid stimulating hormone among different types of kidney pathology (both P<0.05); compared with types I LN, the serum level of free triiodothyronine was lower in types Ⅳ LN (3.4 (2.8, 3.9) vs. 4.3 (3.7, 5.5) pmol/L, Z=3.75, P<0.05). The serum level of free triiodothyronine was negatively correlated with the acute activity index score of lupus nephritis ( r=-0.228, P<0.05), while the serum level of thyroid stimulating hormone was positively correlated with the renal pathological acute activity index score of lupus nephritis ( r=0.257, P<0.05). Conclusions:There is a high incidence of thyroid dysfunction in childhood SLE patients. The higher SLEDAI and more severe renal damage were found in SLE patients with thyroid dysfunction compared to these with normal thyroid functions. The risk factors of childhood SLE with thyroid dysfunction are the higher level of triglyceride and D-dimer. The serum level of thyroid hormone is possibly related to the kidney injury of LN.