Meta-analysis Of Relationship Between Hypothyroidism And Non-alcoholic Fatty Liver Disease

Objectives:Non-alcoholic fatty liver disease(NAFLD)is one of the most common chronic liver diseases.Hypothyroidism is closely related to the components of metabolic syndrome.Considering the liver manifestations of metabolic syndrome,some studies have investigated the relationship between hypothyroidism andNAFLD.Previous studies have suggested that hypothyroidism may play a key role in the pathogenesis of NAFLD.In addition to this,an increased prevalence of hypothyroidism in NAFLD patients has been observed in some studies.However,the clinical data supporting this association are incomplete,and the pathophysiology on which this association is based is still unclear,and the relationship between hypothyroidism and NAFLDremains controversial in published studies.Therefore,we performed a meta-analysis to better describe the effects of hypothyroidism on the development of NAFLD and its progression to non-alcoholic steatohepatitis(NASH).Methods:Case control study,cross-sectional study and cohort study on the relationship between hypothyroidism and NAFLD were searched in PubMed,EMBASE and Cochrane Library.The retrieval time is from the establishment of the database to May 31,2019.Results:A total of 18 studies were included,including 12 cross-sectional studies,2cohort studies and 4 case-control studies.The results of meta-analysis showed that hypothyroidism(including overt hypothyroidism and subclinical hypothyroidism)was the risk factor of NAFLD(OR=1.37,95%CI 1.16-1.63,P<0.01);There was a correlation between hypothyroidism and nonalcoholic steatohepatitis(NASH)(OR=2.33,95%CI 1.40-3.86,P<0.01).We performed four subgroup analyses of the relationship between hypothyroidism and NAFLD,including types of hypothyroidism,study region,study design,and agepopulation.Subgroup analysis found that overt hypothyroidism and subclinical hypothyroidism(SCH)were independently associated with NAFLD,respectively(OR=1.50,95%CI:1.16-1.94,P=0.480,I~2=0%)and(OR=1.28,95%CI:1.06-1.54,P=0.000,I~2=66.6%);Compared with North America,the hypothyroidism and NAFLD of the population in Asia and Europe are significantly correlated(OR=1.31,95%CI:1.04-1.66,P=0.000,I~2=70.5%and OR=1.46,95%CI:1.07-1.99,P=0.058,I~2=50.8%),the heterogeneity is higher;Compared with the cohort study,the case-control study and the cross-sectional study showed a significant correlation between hypothyroidism and NAFLD.The values were(OR=2.65,95%CI:1.61-4.35,P=0.090,I~2=53.8%)and(OR=1.27,95%CI:1.04-1.54,P=0.033,I~2=45.4%);Hypothyroidism is a risk factor for NAFLD in adults,children or adolescents,with values of(or=1.30,95%CI:1.10-1.54,P=0.000,I~2=62.6%)and(or=2.41,95%CI:1.55-3.76,P=0.379,I~2=0%).Sensitivity analysis suggested that the results of this study were stable.There was no significant publication bias in this study.Conclusions:Hypothyroidism may increase the risk of NAFLD and NASH.Overt hypothyroidism and SCH are independently related to NAFLD.