Thyroid Function and Risk of Non-Alcoholic Fatty Liver Disease in Euthyroid Subjects

Abstract

Introduction and aims. The association between thyroid function and non-alcoholic fatty liver disease (NAFLD) remained controversial. A large cross-sectional study aimed to explore the relationship in euthyroid population. Material and methods. A total of 1773 euthyroid subjects who underwent health check-up during one-year period were enrolled. NAFLD was diagnosed by ultrasound and fatty liver index (FLI). Fibrosis was estimated by BARD score. Thyroid function parameters, including thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), and free thyroxine (FT4), were recorded. Multivariate logistic regression analyses were performed to identify the independent risk factors. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated. Results. NAFLD was diagnosed by ultrasound in 638 (35.98%) subjects and by FLI ≥ 60 in 694 (39.14%) subjects. Regardless of ultrasound or FLI, the overall analysis demonstrated that TSH and FT3 levels were significantly higher in subjects with NAFLD than subjects without NAFLD, but FT4 level was not significantly different between them. This association remained in middle-age subjects, but not elderly subjects. In the multivariate logistic regression analysis, TSH (OR = 1.108, 95%CI = 1.056-1.398, P = 0.024) and FT3 (OR = 1.258, 95%CI = 1.123-1.409, P = 0.000) levels were independently associated with the risk of NAFLD diagnosed by ultrasound; and only FT3 level (OR = 1.252, 95%CI = 1.074 - 1.460, P = 0.004) was independently associated with the risk of NAFLD estimated by FLI ≥ 60. Additionally, FT3 level (OR = 1.178, 95%CI = 1.025 - 1.354, P = 0.021) was independently associated with the risk of fibrosis estimated by BARD score ≥ 2 in NAFLD subjects. Conclusion. Among the euthyroid population, FT3 and TSH levels were positively associated with the risk of NAFLD.

Free triiodothyronine is associated with the occurrence and remission of nonalcoholic fatty liver disease in euthyroid women

“…3 Two Chinese studies and one Dutch study found a positive association between high-normal FT3 levels and NAFLD, where the latter used the fatty liver index to identify NAFLD. [8][9][10] Our results documented this positive association in euthyroid women but not in euthyroid men. We further combined NAFLD with ALT levels and with the FIB-4 index.…”

“…This was in accordance with the study by Liu et al They found that BARD score estimated risk of fibrosis was positively associated with FT3 levels in euthyroid NAFLD subjects. 10 Because visceral adiposity was an established risk factor for NAFLD and was also related to high-normal FT3, 24,28 it may be a confounding factor of the association between NAFLD and thyroid hormones. We adjusted VFA instead of BMI in Model 2 and found that the positive associations between FT3 and NAFLD still existed.…”

“…4,5 However, the conclusions from the studies regarding the association of free triiodothyronine (FT3), the bioactive form of thyroid hormones, with NAFLD in euthyroid subjects remained inconsistent. [6][7][8][9] Previous studies in Chinese 8,10 and Dutch people 9 showed that high-normal FT3 levels were associated with the risk of NAFLD, but other studies did not find the same association. 6,7 In addition, most of the studies showed that lower free thyroxine (FT4) 6,7,9 and higher TSH 7,9,10 levels within the normal range were associated with the risk of NAFLD in euthyroid adults.…”