Nonalcoholic Fatty Liver Disease Is Not Associated with Thyroid Hormone Levels and Hypothyroidism: A Systematic Review and Meta-Analysis

Abstract

Background: Whether hypothyroidism is related to nonalcoholic fatty liver disease (NAFLD) is unclear. Thyroid dysfunction is closely related with components of metabolic syndrome. Given the hepatic manifestation of metabolic syndrome, several studies have investigated the association between NAFLD and thyroid dysfunction and have demonstrated inconsistent results. Thus, we conducted a systematic review and meta-analysis to better characterize the association between NAFLD and thyroid dysfunction. Methods: MEDLINE and Embase were searched through July 2016. The primary outcome was the association between NAFLD and subclinical, overt, and overall hypothyroidism. The secondary outcome was the difference in thyroid hormone levels (free triiodothyronine [FT₃], free thyroxine [FT₄], or thyroid-stimulating hormone [TSH]) between NAFLD patients and non-NAFLD controls. Pooled odds ratios (OR) and 95% CI were calculated using a random-effects model. All continuous data are summarized as the mean difference along with 95% CI. Results: Data were extracted from 14 studies involving 7,191 NAFLD patients and 30,003 controls. NAFLD was not associated with subclinical, overt, or overall hypothyroidism compared with non-NAFLD controls. Patients who had NAFLD did not show a significant difference in FT₃, FT₄, or TSH compared with non-NAFLD controls. Conclusions: Our meta-analysis demonstrates no significant association between NAFLD and subclinical, overt, or overall hypothyroidism, and we also found no significant difference in thyroid hormone levels between participants with and without NAFLD.

Association Between Primary Hypothyroidism and Nonalcoholic Fatty Liver Disease: A Systematic Review and Meta-Analysis

“…Two previous smaller meta-analyses have yielded controversial findings (25,26]. One meta-analytic study of nine studies (involving a total of *32,000 subjects) showed that patients with NAFLD had no significant differences in serum thyroid hormone levels compared with control individuals and that there was no significant association between variably defined primary hypothyroidism and NAFLD (random-effects OR 1.21 [CI 0.91-1.61]; I 2 = 72%) (25). Compared with our meta-analysis, the authors have included six identical studies to those included in our meta-analysis (11,13,14,16,18,19), but also three cross-sectional studies (31-33) that we have excluded for the reasons specifically reported in supplementary Table 1.…”

“…Our meta-analysis exploring the association between variably defined primary hypothyroidism and the risk of NAFLD is the largest and most comprehensive assessment to date. Two previous smaller meta-analyses have yielded controversial findings (25,26]. One meta-analytic study of nine studies (involving a total of *32,000 subjects) showed that patients with NAFLD had no significant differences in serum thyroid hormone levels compared with control individuals and that there was no significant association between variably defined primary hypothyroidism and NAFLD (random-effects OR 1.21 [CI 0.91-1.61]; I 2 = 72%) (25).…”

“…This finding raised concern as to whether subclinical hypothyroidism could be associated with an increased risk of NAFLD. Although two previous small meta-analyses have further explored this question, they had important methodological limitations (e.g., pooling of cross-sectional and longitudinal studies; very high heterogeneity and significant publication bias of results) and did not consider much of the currently available evidence (i.e., studies published in 2017 and 2018), thus providing controversial and inconclusive findings (25,26). On this background of evidence, it still remains uncertain whether subclinical hypothyroidism is a risk factor for NAFLD.…”

Role of hypothyroidism in the onset of metabolic syndrome and hepatic steatosis

“…Hipotiroidizmom indukovani elementi metaboličkog sindroma predisponiraju razvoj hepatične steatoze. [19][20][21][22][23][24]…”

Protection of recombinant human erythropoietin toward rats with reducedsize liver transplantation for fatty liver

“…The disease causes serious threat to human life and health. Fatty liver is caused by obesity, alcohol, diabetes, drugs, and other factors [1,2]. Recently, the morbidity of fatty liver in China has steadily increased and has occurred in younger populations.…”