Alterations in thyroid hormone indices were associated with glycemic status in individuals with nonalcoholic fatty liver disease. A retrospective analysis published in Diabetes, Metabolic Syndrome and Obesity evaluated the relationship between thyroid hormones (THs), particularly the free triiodothyronine to free thyroxine ratio (FT3/FT4), and type 2 diabetes mellitus (T2DM) in patients with nonalcoholic fatty liver disease (NAFLD).

The analysis included 4942 hospitalized patients with NAFLD between 2020 and 2023. Partial correlation analysis adjusted for age and sex assessed associations of THs and FT3/FT4 with hemoglobin A1c (HbA1c) and fasting blood glucose (FBG). Binary logistic regression evaluated the relationship between FT3/FT4 and T2DM, and receiver operating characteristic (ROC) analysis assessed its discriminatory performance.

Compared with individuals without T2DM, those with T2DM had lower levels of free triiodothyronine (FT3), total triiodothyronine (TT3), and FT3/FT4 ratio, and higher free thyroxine (FT4). FT3, TT3, and FT3/FT4 were inversely correlated with HbA1c and FBG, with FT3/FT4 showing the strongest correlation with HbA1c (r = −0.222; P < 0.001).

After adjustment for confounding variables, individuals in the highest FT3/FT4 quartile had lower odds of T2DM compared with those in the lowest quartile (odds ratio 0.27; 95% confidence interval 0.23-0.33; P < 0.001). The FT3/FT4 ratio demonstrated moderate discrimination for T2DM, with area under the curve values up to 0.668.

A lower FT3/FT4 ratio was associated with T2DM and higher glycemic measures in NAFLD, and showed stronger associations than individual thyroid hormone levels.