The Interrelation Between Hypothyroidism and Non-alcoholic Fatty Liver Disease, a Cross-sectional Study.

Background: Thyroid hormones play an important role in the regulation of diverse metabolic processes and might play a crucial role in the pathogenesis of non-alcoholic fatty liver disease (NAFLD). However, their association remains controversial. Therefore, our aim is to clarify whether overt or subclinical hypothyroidism was associated with NAFLD.

Methods: This cross-sectional study included 60 participants with a new diagnosis of hypothyroidism and 30 age- and gender-matched healthy participants with thyroid-stimulating hormone (TSH) level <4.5 mIU/L. Anthropometric measurements, laboratory parameters, plasma fibroblast growth factor 21 (FGF21), and hepatic steatosis diagnosed via controlled attenuation parameter (CAP) using transient elastography between the hypothyroid groups and control group were analyzed.

Results: Participants with hypothyroidism displayed significantly higher serum aspartate aminotransferase, alanine aminotransferase, gamma glutamyl transferase, total cholestrol, triglycerides, low-density lipoprotein cholesterol, TSH, hemoglobin A1c, fasting insulin, and homeostatic model assessment of insulin resistance (HOMA-IR) but significantly lower serum albumin, high-density lipoprotein cholesterol, and free thyroxine levels than the control group ( = <0.001). The CAP values were significantly higher in participants with overt and subclinical hypothyroidism than the control group ( = <0.001). The only significant independent predictors of steatosis in our study were free T4, body mass index, and HOMA-IR after using multivariate logistic regression. The mean serum FGF21 levels were increased in hypothyroid participants with hepatic steatosis than those without hepatic steatosis (126.9 ± 272.6) pg/ml vs. (106.8 ± 138.7) pg/ml,  = 0.8). Receiver operating characteristic (ROC) curve showed that FGF21 was not a significant marker for hepatic steatosis in hypothyroid participants (area under curve (AUC) = 0.44,  = 0.54).

Conclusion: Individuals with subclinical or overt hypothyroidism were more likely to have NAFLD than those with normal thyroid function. Serum FGF21 levels were increased in hypothyroid individuals and its role as a marker of hepatic steatosis in hypothyroid individuals needs further assessment.