Lower Free Triiodothyronine is a Risk Factor of Diabetic Peripheral Neuropathy in Patients with Type 2 Diabetes Mellitus.

Purpose: Our objective is to investigate the potential involvement of free triiodothyronine (FT3), a key bioactive compound found in thyroid hormones (THs) in the pathogenesis of diabetic peripheral neuropathy (DPN) in patients diagnosed with type 2 diabetes mellitus (T2DM).

Patients and methods: A total of 121 T2DM patients were recruited. And then, they were divided into the control group and the DPN group. Clinical parameters were collected for each patient. Additionally, nerve conduction velocity was tested using neurophysiological methods. Correlation and regression analyses were employed to examine the relationship between the concentrations of FT3 and DPN.

Results: Compared to 57 patients without DPN, 64 patients with DPN showed increased HbA1c and low-density lipoprotein cholesterol (LDL-C) levels (P=0.001 and 0.042), as well as decreased concentrations of FT3 (P=0.042). Additionally, FT3 levels are positively associated with the motor and sensory fibers conduction velocity of the Ulnar nerve, as well as the motor conduction velocity of the Tibial nerve, with (R=0.205, P=0.025; R=0.191, P=0.038; R=0.220, p=0.016) or without (R=0.257, P=0.004; R=0.227, P=0.012; R=0.227, p=0.012) adjustment for HbA1c and LDL-C. Furthermore, multiple linear regression analysis suggests that decreased FT3 levels may influence the motor and sensory fibers conduction velocity of the Ulnar nerve (β=0.795, P=0.025 and β=0.909, P=0.038), as well as the motor conduction velocity of the Tibial nerve (β=0.727, P=0.016). Moreover, our study demonstrated that decreased FT3 levels are one of the risk factors for DPN in T2DM patients, as determined by binary logistic regression analysis (OR=0.542, P=0.022).

Conclusion: Lower concentrations of FT3 are one of the risk factors for DPN in patients with T2DM. Additionally, decreased FT3 levels may influence peripheral neuropathy, particularly affecting the motor and sensory fibers conduction velocity of the ulnar nerve, as well as the motor fiber conduction velocity of the tibial nerve.