Correlation between diabetic peripheral neuropathy and thyroid hormone sensitivity in elderly patients with type 2 diabetes mellitus

Abstract

Background: Diabetic peripheral neuropathy (DPN) is a common complication of type 2 diabetes mellitus (T2DM), significantly affecting patients' quality of life and imposing a substantial economic burden. Recent studies have highlighted the role of thyroid hormones in diabetes complications, particularly in elderly patients with T2DM. However, the relationship between thyroid hormone sensitivity and DPN remains unclear.

Aim: To investigate the correlation between thyroid hormone sensitivity and DPN in elderly patients with T2DM.

Methods: In a cohort of 256 elderly patients with T2DM, propensity score matching was used to balance age, sex, and diabetes duration. Clinical data were collected to calculate thyroid hormone sensitivity and analyze its correlation with DPN. A random forest model was used to evaluate the diagnostic value of free triiodothyronine/free thyroxine (FT₃/FT₄) for DPN.

Results: Patients with DPN had a lower FT₃/FT₄ ratio [ (0.302 ± 0.053) vs (0.316 ± 0.049), P = 0.040]. Quartile stratification showed decreasing DPN prevalence with higher FT₃/FT₄ ratios. Spearman's correlation analysis showed that a lower FT₃/FT₄ ratio was associated with higher glycated hemoglobin, fasting blood glucose, reduced nerve conduction velocity, and electrical skin conductance. Logistic regression indicated a positive relationship between the median FT₃/FT₄ ratio and bilateral foot electrochemical skin conductance [odds ratio (OR): 1.019; 95%CI: 1.005-1.034; P = 0.007] and sural nerve sensory amplitude (OR: 1.310; 95%CI: 1.008-1.703; P = 0.043). Receiver operating characteristic analysis using a random forest model showed that incorporating FT₃/FT₄ improved predictive performance for DPN, with an area under the curve of 0.74, sensitivity of 0.79, specificity of 0.64, and accuracy of 0.77.

Conclusion: In elderly patients with T2DM with euthyroidism, a lower FT₃/FT₄ ratio is correlated with increased DPN incidence, affecting both large and small nerve fibers. FT₃/FT₄ is an effective predictor of DPN.

Keywords: Diabetic peripheral neuropathy; Elderly; Free triiodothyronine/free thyroxine ratio; Thyroid hormone sensitivity; Type 2 diabetes mellitus.

Figure 1

Flow diagram showing the selection of the study population. DPN: Diabetic peripheral neuropathy; NDPN: Non diabetic peripheral neuropathy; PSM: Propensity score matching; T2DM: Type 2 diabetes mellitus.

Figure 2

Receiver operating characteristic curve of free triiodothyronine/free thyroxine for predicting diabetic peripheral neuropathy. The receiver operating characteristic (ROC) curve plotted based on the random forest model evaluates the value of free triiodothyronine/free thyroxine (FT₃/FT₄) in predicting DPN. First, we used age, sex, duration of diabetes, hypertension, smoking, low-density lipoprotein cholesterol, triglycerides, hormglycated, fasting blood glucose, and body mass index to construct the model and generate the ROC curve (labeled as “original”). Then, we included FT₃/FT₄ as an additional feature in the model and generated a new ROC curve (labeled as “FT₃/FT₄”). ROC: Receiver operating characteristic; AUC: Area under the curve; FT₃/FT₄: Free triiodothyronine/free thyroxine ratio.