Lower levels of Free Triiodothyronine tied to Peripheral Neuropathy in Diabetics, suggests study

Diabetic peripheral neuropathy (DPN) is a common cause of neuropathy worldwide. Literature shows that thyroid function abnormality can affect glucose metabolism, leading to complications in type 2 diabetics. Triiodothyronine (T3), one of the main active ingredients of thyroid hormones, is necessary for nerve survival. Previous research has shown that free triiodothyronine is a predictive factor for peripheral neuropathy in diabetics. As the role of free triiodothyronine (FT3) in nerve injury is not elucidated, researchers conducted a study to investigate the effect of FT3 on DPN, particularly on the conduction velocity of nerve fibers in T2DM patients without thyroid disease.

A cross-sectional study was carried out at the Department of Endocrinology, The First Affiliated Hospital of USTC, by recruiting 121 patients with T2DM. Among these, 64 were diagnosed with DPN, while 57 were not diagnosed with DPN despite having T2DM (controls). Neuropathy caused by any cause other than diabetes was excluded from the study. The participants were divided into the control group and the DPN group. Clinical parameters like age, gender, diabetes mellitus (DM) duration, and biochemical parameters were collected for each patient. Additionally, nerve conduction velocity was tested using neurophysiological methods, such as an electromyographic evoked potential meter. Correlation and regression analyses were employed to examine the relationship between the concentrations of FT3 and DPN. Binary logistic regression analysis was carried out to investigate the risk factors for DPN in T2DM patients. Multiple linear regression analyses were performed to explore further factors influencing nerve conduction fiber velocity.

Findings:

• The DPN patients 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) when compared to the controls.
• FT3 levels were positively associated with the motor and sensory fibers conduction velocity of the Ulnar nerve and the motor conduction velocity of the Tibial nerve, with or without adjustment for HbA1c and LDL-C.
• As per the multiple linear regression analysis, decreased FT3 levels may influence the motor and sensory fibers' conduction velocity of the Ulnar nerve and the motor conduction velocity of the Tibial nerve.
• The binary logistic regression analysis demonstrated that decreased FT3 levels are one risk factor for DPN in T2DM patients.

Thus, this is the first study to report the association between FT3 and DPN in terms of specific nerve fiber injury in T2DM patients. The study concluded that lower FT3 concentration is a risk factor for DPN in T2DM patients. The study underscores the importance of monitoring the FT3 levels in diabetics for early identification of DPN. The authors also suggested that further research may be necessary to identify diagnostic criteria and treatment thresholds in diabetics with peripheral neuropathy.

Further reading: Chen Y, Sun L, Chen M, et al. 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. Published 2024 Nov 25. doi:10.2147/DMSO.S489204.