Non-alcoholic fatty liver disease and thyroid dysfunction: a systematic review

Abstract

Thyroid hormones are totally involved in the regulation of body weight, lipid metabolism, and insulin resistance. Therefore it is anticipated that thyroid hormones may have a role in the pathogenesis of non alcoholic fatty liver disease (NAFLD) and non alcoholic steatohepatitis (NASH). In this study, we reviewed the current literature on the association between thyroid dysfunction and NAFLD/NASH. A search for English language medical literature reporting an association between thyroid dysfunction and NAFLD/NASH in humans was conducted across PubMed, ISI Web of Science, and Scopus in August, 2013. Out of 140 studies initially identified through the search, 11 relevant articles were included in the final review. Thyroid dysfunctions in the form of overt or subclinical hypothyroidism are prevalent among patients with NAFLD/NASH. Hypothyroidism appears to be an independent risk factor for NAFLD/NASH in some studies; however, other newly published studies failed to find such an association. The results of the studies on the role of thyroid abnormalities in NAFLD/NASH are inconsistent, and further research is recommended to determine the relationship between hypothyroidism and NAFLD/NASH and the underlying mechanisms.

Keywords: Hypothyroidism; Non alcoholic fatty liver disease; Non alcoholic steatohepatitis; Pathophysiology; Risk factor; Thyroid dysfunction.

Figure 1

Flow diagram of the review.

Figure 2

Possible mechanisms involved in association between hypothyroidism and non-alcoholic fatty liver disease/non alcoholicsteatohepatitis. NAFLD: Non-alcoholic fatty liver disease; NASH: Non alcoholicsteatohepatitis; ROS: Reactive oxygen species; FGF-21: Fibroblast growth factor-21; LPL: Lipoprotein Lipase; TG: Triglyceride; Chol: Cholesterol; IR: Insulin resistance.