Thyroid diseases and risk of peripheral neuropathy in a large population-based cohort: evidence from the UK Biobank.

Background: Thyroid dysfunction has been linked to several neurological disorders, but the association between thyroid diseases and peripheral neuropathy remains insufficiently explored in large population-based cohorts. We aim to investigate the association between thyroid diseases and peripheral neuropathy. Methods: We analyzed 498,417 complete-case participants from the UK Biobank with linked hospital diagnosis records. Thyroid diseases were defined using ICD-10 codes, including hypothyroidism, hyperthyroidism, and thyroid cancer. Peripheral neuropathy was identified using ICD-10 codes G60-G64. Multivariable logistic regression models were used to estimate odds ratios (ORs) and 95% confidence intervals (CIs). Results: Peripheral neuropathy was identified in 6,341 participants. In the fully adjusted model including demographic, lifestyle, socioeconomic, and clinical covariates, hypothyroidism was significantly associated with peripheral neuropathy (OR 1.29, 95% CI 1.18-1.40), and hyperthyroidism showed a weaker but statistically significant association (OR 1.22, 95% CI 1.01-1.45). Thyroid cancer was not significantly associated with peripheral neuropathy (OR 1.16, 95% CI 0.66-1.89). In sensitivity analyses excluding participants with diabetes, hypothyroidism remained associated with peripheral neuropathy, whereas the association for hyperthyroidism was attenuated. Discussion: Clinically diagnosed hypothyroidism and hyperthyroidism were associated with higher odds of peripheral neuropathy in this UK Biobank-based analysis. These findings should be interpreted as associations rather than causal relationships, given the observational design and lack of thyroid hormone levels, disease severity, and treatment information.