Association between hypothyroidism and liver fibrosis risk: a systematic review and meta-analysis

Aim of the study
Non-alcoholic fatty liver disease (NAFLD), which encompasses a wide variety of liver pathology, is now the most common chronic liver disease worldwide. The presence of hypothyroidism has been linked to the development of NAFLD. However, its correlation with liver fibrosis, an important clinical entity in NAFLD, is less clear. We aimed to summarize the association between hypothyroidism and liver fibrosis risk.

Material and methods
We conducted a search of PubMed and ProQuest from inception to June 30, 2021, for studies assessing the association between hypothyroidism and liver fibrosis risk. The quality of included studies was evaluated using the Newcastle-Ottawa Scale (NOS). We analyzed the pooled odds ratios (ORs) with 95% confidence intervals (CIs) using a fixed and random-effects model. Heterogeneity was assessed using I2.

Results
Eight studies with a total of 14,588 patients were included. The quality of studies ranged from 6 to 8 stars. Thyroid stimulating hormone (TSH) ≥ 2.5 was significantly associated with increased risk of significant liver fibrosis (OR = 1.61, 95% CI = 1.21-2.15). Subclinical hypothyroidism was also correlated with an increased risk of advanced fibrosis (OR = 2.77, 95% CI = 1.65-4.65). A significant association was found between overt hypothyroidism and non-alcoholic steatohepatitis (NASH) risk (OR = 2.38, 95% CI = 1.61-3.53). However, no significant association was found between subclinical hypothyroidism and significant liver fibrosis.

Conclusions
Hypothyroidism is associated with an increased risk of fibrosis in NAFLD patients.