Low thyroid function is associated with an increased risk of advanced fibrosis in patients with metabolic dysfunction-associated fatty liver disease

Aims Observational studies showed that low thyroid function may perturb liver function. We aimed to evaluate the association of low thyroid function with both metabolic dysfunction-associated fatty liver disease (MAFLD) and advanced hepatic fibrosis.Methods Participants who underwent abdominal ultrasonography and thyroid function test in a Chinese hospital from 2015 to 2021were enrolled. Fibrosis-4 index (FIB-4) > 2.67 and/or non-alcoholic fatty liver disease fibrosis score (NFS) > 0.676 were used to define advanced fibrosis. Descriptive analyses were performed to characterize the epidemiology of MAFLD according to levels of thyroid-stimulating hormone (TSH). The logistic regression model was applied to estimate the association of low thyroid function with MAFLD and advanced fibrosis.Results A total of 19,946 participants (52.78% males, mean age: 47.31 years, 27.55% MAFLD) were included, among which 14,789 were strict-normal thyroid function, 4,328 were low-normal thyroid function, 829 were subclinical hypothyroidism. TSH levels were significantly higher in MAFLD patients with a FIB-4 > 2.67 and /or NFS > 0.676 than their counterparts. The logistic regression model adjusted for age and sex showed that low-normal thyroid function increased the risk of MAFLD (odds ratio [OR] = 1.09; 95% confidence interval [CI] 1.01-1.18). Multivariable regression model adjusted for age, sex, body mass index, type 2 diabetes, and hypertension showed low-normal thyroid function increased the risk of advanced fibrosis in patients with MAFLD (FIB-4 > 2.67: OR = 1.41, 95% CI 1.02-1.93; NFS > 0.676: OR = 1.72, 95% CI 1.08-2.72).Conclusion Elevated TSH concentrations are associated with advanced hepatic fibrosis, even in the euthyroid state.