Association of non-alcoholic fatty liver disease with thyroid function: A systematic review and meta-analysis

Abstract

Background: Nonalcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases. The relationship of NAFLD with thyroid function parameters and hypothyroidism remains controversial.

Aim: To clarify the effect of thyroid function parameters and hypothyroidism on the development of NAFLD and progression to nonalcoholic steatohepatitis (NASH).

Methods: PubMed, EMBASE, and Cochrane library databases were searched. Study quality was assessed. Weighted mean difference (WMD) and odds ratio (OR) with 95% confidence interval (CI) were calculated.

Results: Twenty six studies involving 61,548 participants were eligible, most of which were of high quality. NAFLD/NASH patients had significantly higher TSH levels than controls in adults (NAFLD versus health: WMD = 0.105, 95%CI = 0.012-0.197; NAFLD versus euthyroidism: WMD = 0.100, 95%CI = 0.005-0.194; NASH versus NAFLD: WMD = 0.540, 95%CI = 0.136-0.944) and children/adolescents (NAFLD versus lean controls: WMD = 1.039, 95%CI = 0.104-1.973; NAFLD versus overweight/obese controls: WMD = 0.485, 95%CI = 0.267-.703). Unclassified hypothyroidism was positively associated with the risk of NAFLD/NASH in adults (NAFLD versus health: OR = 1.605, 95%CI = 1.180-2.183; NASH versus NAFLD: OR = 2.317, 95%CI = 1.425-3.768) and children/adolescents (NAFLD versus overweight/obese controls: OR = 2.015, 95%CI = 1.246-3.258). However, the statistical results were inconsistent among the subgroup meta-analyses of subclinical and overt hypothyroidism. Association of NAFLD with FT3 and FT4 levels was heterogeneous among population.

Conclusion: TSH level may be an important risk factor for the development and progression of NAFLD, independent of thyroid hormones.

Keywords: Hypothyroidism; Metabolism; Nonalcoholic steatohepatitis; Thyroid-stimulating hormone.