Low Free Triiodothyronine Levels Linked to Increased Risk of Diabetic Peripheral Neuropathy in Type 2 Diabetes: Study

In a study examining T2DM patients, those with DPN had significantly lower FT3 levels than those without the condition. Furthermore, reduced FT3 levels were independently associated with impaired conduction of motor and sensory fibers, particularly in the ulnar and tibial nerves.

Yang Chen, University of Science and Technology of China, Hefei, People’s Republic of China, and colleagues aimed to investigate the potential involvement of free triiodothyronine, a key bioactive compound found in thyroid hormones (THs) in the pathogenesis of diabetic peripheral neuropathy in patients diagnosed with type 2 diabetes mellitus.

For this purpose, the researchers recruited 121 patients with T2DM, who were then divided into a control group and a DPN group. Clinical parameters were collected for each participant, and nerve conduction velocity was assessed using neurophysiological techniques. To analyze the relationship between FT3 concentrations and diabetic peripheral neuropathy, the researchers employed correlation and regression analyses.

The investigation led to the following findings:

• Compared to 57 patients without DPN, 64 patients with DPN had higher HbA1c and low-density lipoprotein cholesterol (LDL-C) levels and lower FT3 concentrations.
• FT3 levels were positively correlated with motor and sensory fiber conduction velocity in the ulnar nerve (R=0.205) and motor conduction velocity in the tibial nerve (R=0.191), both with and without adjustment for HbA1c and LDL-C.
• Multiple linear regression analysis showed lower FT3 levels were associated with reduced conduction velocity in the ulnar nerve (β=0.795; β=0.909) and tibial nerve (β=0.727).
• Binary logistic regression analysis identified decreased FT3 levels as a significant risk factor for DPN in T2DM patients (OR=0.542).

According to the authors, the study is the first to establish a connection between FT3 levels and diabetic peripheral neuropathy (DPN), specifically regarding nerve fiber damage in patients with type 2 diabetes mellitus (T2DM). It identifies lower FT3 concentrations as a risk factor for DPN in T2DM patients without diagnosed thyroid diseases (other than thyroid nodules). Furthermore, reduced FT3 levels may influence peripheral neuropathy, particularly the motor and sensory conduction velocities of the ulnar nerve and the motor conduction velocity of the tibial nerve in euthyroid T2DM patients.

"The study also highlights the potential interactive effects of FT3 and DPN in this population, urging further research to define appropriate reference ranges for thyroid hormones, including FT3, in the context of DPN," they concluded.

Reference:

Chen Y, Sun L, Chen M, Zhang H, Song B, Wang H, Jiang A, Zhang L, Li S, Wang J, Wang W, Zhang H. Lower Free Triiodothyronine is a Risk Factor of Diabetic Peripheral Neuropathy in Patients with Type 2 Diabetes Mellitus. Diabetes Metab Syndr Obes. 2024;17:4407-4415

https://doi.org/10.2147/DMSO.S489204