AUTHOR=Liu Huan-Xin , Ren Yan-Yan , Meng Cui-Qiao , Li Zhong , Nie Qian , Yu Chun-Hong , Ma Hui-Juan 

TITLE=Mediating effect analysis of visceral adiposity index on free triiodothyronine to free thyroxine ratio and non-alcoholic fatty liver disease in euthyroid population

JOURNAL=Frontiers in Endocrinology

VOLUME=Volume 13 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/endocrinology/articles/10.3389/fendo.2022.961803

DOI=10.3389/fendo.2022.961803

ISSN=1664-2392

ABSTRACT=Background: The association between free triiodothyronine/free thyroxine (FT3/FT4) and non-alcoholic fatty liver disease (NAFLD) in euthyroid subjects is unclear. In addition, few studies have explored whether VAI mediates the association between FT3/FT4 ratio and NAFLD in euthyroid population. We aimed to analyze the mediating effect of VAI on FT3/FT4 ratio and NAFLD risk in euthyroid population. 
Methods: A total of 7 946 annual health examinees were selected from the Health Examination Center, Hebei General Hospital from January to December 2020. The basic information, physical examination and biochemical parameters, as well as calculated FT3/FT4 ratio and VAI were collected. NAFLD was diagnosed according to abdominal ultrasonography. The risk of NAFLD was analyzed by quartiles of SUA/Scr ratio (Q1-Q4 quartiles) and VAI (V1-V4 quartiles), respectively. Pearson correlation analysis was used to explore the correlation between FT3/FT4 ratio and VAI. Multivariate logistic regression analysis was used to explore the effect of FT3/FT4 ratio and VAI on NAFLD. Bootstrap was used to explore whether VAI mediated the association between FT3/FT4 ratio and NAFLD. 
Results: Of the 7 946 participants, 2 810 (35.36%) had NAFLD and 5 136 (64.64%) did not. Pearson correlation analysis indicated that FT3/FT4 ratio was positively associated with VAI (P<0.05). Multivariate logistic regression analysis indicated that compared with Q1 group, the risk of NAFLD significantly increased in Q3 group 〔OR=1.408, 95%CI (1.185, 1.672)〕 and Q4 group 〔OR=1.728, 95%CI (1.453, 2.055)〕 (P<0.01). Compared with V1 group, the risk of NAFLD notably increased in V2 group 〔OR=1.746, 95%CI (1.394, 2.187)〕, V3 group 〔OR=2.589, 95%CI (2.033, 3.297)〕 and V4 group 〔OR=4.497, 95%CI (3.299, 6.129)〕 （P<0.01）. Mediating effect analysis showed that FT3/FT4 ratio significantly, directly influenced NAFLD prevalence 〔β=3.7029, 95%CI (2.9583, 4.4474)〕, and VAI partly mediated the indirect effect of FT3/FT4 ratio on NAFLD prevalence 〔β=2.7649, 95%CI (2.2347, 3.3466)〕, and the mediating effect accounted for 42.75% of the total effects. 
Conclusion: Both FT3/FT4 ratio and VAI were predictors of NAFLD, and VAI partly mediated the indirect effect of FT3/FT4 ratio on NAFLD prevalence in euthyroid population.