Association of thyroid function with non‐alcoholic fatty liver disease in recent‐onset diabetes

Abstract Background and Aims Non‐alcoholic fatty liver disease (NAFLD) has been linked to type 2 diabetes (T2D), but also to hypothyroidism. Nevertheless, the relationship between thyroid function and NAFLD in diabetes is less clear. This study investigated associations between free thyroxine (fT4) or thyroid‐stimulating hormone (TSH) and NAFLD in recent‐onset diabetes. Methods Participants with recent‐onset type 1 diabetes (T1D, n = 358), T2D ( n = 596) or without diabetes (CON, n = 175) of the German Diabetes Study (GDS), a prospective longitudinal cohort study, underwent Botnia clamp tests and assessment of fT4, TSH, fatty liver index (FLI) and in a representative subcohort 1 H‐magnetic resonance spectroscopy. Results First, fT4 levels were similar between T1D and T2D ( p = .55), but higher than in CON (T1D: p < .01; T2D: p < .001), while TSH concentrations were not different between all groups. Next, fT4 correlated negatively with FLI and positively with insulin sensitivity only in T2D ( ß = −.110, p < .01; ß = .126, p < .05), specifically in males ( ß = −.117, p < .05; ß = .162; p < .01) upon adjustments for age, sex and BMI. However, correlations between fT4 and FLI lost statistical significance after adjustment for insulin sensitivity (T2D: ß = −.021, p = 0.67; males with T2D: ß = −.033; p = .56). TSH was associated positively with FLI only in male T2D before ( ß = .116, p < .05), but not after adjustments for age and BMI ( ß = .052; p = .30). Conclusions Steatosis risk correlates with lower thyroid function in T2D, which is mediated by insulin resistance and body mass, specifically in men, whereas no such relationship is present in T1D.