Peripheral Neuropathy in Patients with Diabetes: Clinical Spectrum and Association with Vitamin B12 Deficiency and Hypothyroidism

Abstract

Background: Peripheral neuropathy may occur with diabetes mellitus and cause foot ulceration, functional disability, gait disturbance, pain, and sensory loss, and is one of the most common chronic complications of diabetes mellitus. While long-standing hyperglycemia is an important precipitating factor, other potentially reversible causes like vitamin B12 deficiency and hypothyroidism can play a role in the onset or exacerbation of neuropathic symptoms.

Objective: To evaluate the clinical spectrum of peripheral neuropathy in patients with diabetes mellitus and determine its association with vitamin B12 deficiency and hypothyroidism.

Methodology: This cross-sectional analytical study was conducted at Muhammad Teaching Hospital, Peshawar, from January 2025 to June 2025. The total number of patients enrolled was 67 diabetic mellitus patients, who were consecutively sampled. Symptoms and signs of peripheral neuropathy were evaluated in participants, including numbness, paresthesias, burning sensation, neuropathic pain, abnormal monofilament sensation, impaired vibration perception, and a decrease in ankle reflexes. Serum vitamin B12 level, thyroid-stimulating immunoglobulin, thyroid-stimulating antibody, HbA1c, and hematological parameters were assessed in the laboratory. Association of neuropathy with vitamin B12 deficiency, hypothyroidism, duration of diabetes, glycemic control, and metformin use were statistically evaluated.

Results: Peripheral neuropathy was identified in 39 patients (58.2%). Numbness was the most frequent manifestation, followed by paresthesia, burning sensation, and impaired vibration perception. Vitamin B12 deficiency was present in 21 patients (31.3%), whereas hypothyroidism was detected in 15 patients (22.4%). Neuropathy occurred in 81.0% of patients with vitamin B12 deficiency compared with 47.8% of those without deficiency (p = 0.011). Similarly, 86.7% of hypothyroid patients had neuropathy compared with 50.0% of euthyroid patients (p = 0.012). Vitamin B12 deficiency, hypothyroidism, diabetes duration greater than 10 years, and HbA1c ≥8% remained significant predictors of neuropathy on multivariable analysis.

Conclusion: Peripheral neuropathy was common among patients with diabetes and was significantly associated with vitamin B12 deficiency and hypothyroidism. Longer duration of diabetes and poor glycemic control were additional contributing factors. Assessment of vitamin B12 and thyroid status may help identify treatable causes that can aggravate neuropathic manifestations in diabetic patients.