Low-normal free thyroxine is associated with a higher prevalence of lower extremity arterial disease in euthyroid type 2 diabetes mellitus

Recent studies suggest that high-normal concentrations of free triiodothyronine (FT3) were associated with a lower prevalence of microangiopathy in adult euthyroid people with type 1 diabetes. This study was performed to identify the association between thyroid hormones and lower extremity arterial disease (LEAD) in euthyroid patients with type 2 diabetes mellitus (T2DM). A total of 1052 euthyroid T2DM patients were enrolled, including 704 patients with LEAD as observation group and 348 patients with T2DM alone as control group. The differences in clinical characteristics, biochemical indexes, thyroid hormone between the two groups were compared. At the same time, the association between the incidence of LEAD and thyroid hormone was analyzed. The data demonstrated that FT4 levels were significantly lower in the LEAD patients than in the without LEAD patients (16.1 vs. 16.5 pmol/L). The logistic regression analysis revealed that free thyroxine (FT4) was significantly associated with the incidence of LEAD in T2DM patients, and the prevalence of LEAD increased gradually from the highest FT4 quartile to the lowest FT4 quartile (P < 0.05). In conclusion, patients with low-normal FT4 had a higher prevalence of diabetic LEAD, suggesting that adjusting FT4 levels may better regulate metabolism and thus reduce lower extremity arterial injury.