Objectives: Nonthyroidal illness syndrome (NTIS), also known as low triiodothyronine (T3) syndrome, frequently affects patients with systemic lupus erythematosus (SLE) and may affect lipid metabolism. Dyslipidemia is highly prevalent and associated with the long-term prognosis of SLE. The aim of the present study was to explore the clinical significance of NTIS on disease activity and dyslipidemia in patients with SLE.
Methods: Clinical and laboratory data were collected retrospectively from 223 patients with SLE. The correlation between free triiodothyronine (FT3), SLE disease activity, and lipid profiles were estimated. The correlation coefficient (r) was calculated using a Pearson's regression model. Univariate and multivariate logistic regression analyses were performed to identify the risk factors for dyslipidemia in SLE.
Results: Serum FT3 levels were negatively correlated with the levels of 24 h urine protein (UP), blood urea nitrogen (BUN), creatinine (Cr) and SLE disease activity index (SLEDAI) (all p < 0.001) in NTIS patients but not in euthyroid patients. ApoB/ApoA1 was significantly correlated with SLEDAI (p < 0.01) in NTIS patients and CRP (p < 0.001) and ESR (p < 0.01) in euthyroid patients. A multivariate analysis revealed that only FT3 exhibited an independent negative association with dyslipidemia (P = 0.01; OR = 0.48; 95% CI 0.27-0.85).
Conclusion: NTIS frequently occurs in patients with SLE. Low FT3 is associated with disease activity in SLE patients complicated with NTIS. Low FT3 is an independent risk factor for dyslipidemia in patients with SLE.