Association Between Thyroid Parameters and Subclinical Atherosclerosis in Hospitalised Euthyroid Patients with Type 2 Diabetes Mellitus

PURPOSE: To explore the association between thyroid parameters and subclinical atherosclerosis (AS) in hospitalised euthyroid patients with type 2 diabetes mellitus (T2DM). PATIENTS AND METHODS: A retrospective analysis was conducted involving 1245 inpatients with T2DM. Free triiodothyronine (FT3), free thyroxine (FT4), and thyroid stimulating hormone (TSH) levels were measured, and carotid artery ultrasonography was performed. Thyroid hormone (TH) sensitivity was evaluated using thyroid feedback quantile-based index (TFQI), TSH index (TSHI), thyrotropin thyroxine resistance index (TT4RI), and free triiodothyronine/free thyroxine ratio (FT3/FT4). RESULTS: In inpatients with T2DM having normal thyroid function, the incidence of subclinical AS declined with increasing levels of FT3, FT4, and FT3/FT4 (P (trend) < 0.05). Logistic regression analysis revealed that FT4 (OR, 0.914; 95% CI, 0.845–0.989), FT3 (OR, 0.374; 95% CI, 0.277–0.504), and FT3/FT4 (OR, 0.036; 95% CI, 0.013–0.061) were independently associated with subclinical AS (P < 0.05). However, TSH, TFQI, TSHI, and TT4RI levels were not associated with subclinical AS (P > 0.05). FT3/FT4 demonstrated superior predictive accuracy for subclinical AS than that of FT3 or FT4 alone (P < 0.001), with a cutoff point of 0.25. CONCLUSION: In euthyroid inpatients with T2DM, subclinical AS exhibited negative correlation with FT3, FT4, and FT3/FT4 levels, independent of other risk factors for AS. Additionally, FT3/FT4 ratio had a good predictive value for subclinical AS.