Evaluation of Nerve Conduction and Cognitive Function in Hypothyroidism and their Correlation with Serum Neurofilament Light Chain

Background: Hypothyroidism is an endocrine disorder defined by insufficient amounts of thyroid hormone. It can affect the peripheral nervous system, evaluated using electrodiagnostic studies and serum neurofilament light chain (NfL), a biomarker of neuronal injury. Cognitive function, including memory and attention, may also be impaired and assessed using the Montreal Cognitive Assessment (MoCA) tool. Objectives: To assess peripheral neuropathy and cognitive dysfunction in hypothyroid patients and to evaluate their association with serum NfL levels. Methods: A case-control study was conducted at Ghazi Al-Hariri Hospital in Baghdad from August 1, 2024, to April 1, 2025, involving 40 hypothyroid patients and 40 controls. All participants underwent sensory and motor nerve conduction studies and MoCA assessment. Serum NfL levels were measured in 20 patients and 20 controls using the ELISA technique. Results: Hypothyroid patients showed significantly higher serum NfL levels (26.49±8.18pg/mL) compared to controls (9.6±1.64pg/mL; p<0.001). Nerve conduction studies revealed slower conduction velocities and prolonged latencies, particularly in the median and sural nerves (p<0.001). Cognitive dysfunction (MoCA < 26) was found in 47.5% of hypothyroid patients and was associated with higher NfL levels (30.23±7.49pg/mL vs. 20.87± 5.77pg/mL; p=0.008). Conclusions: Hypothyroidism is associated with peripheral neuropathy and cognitive impairment, both linked to elevated serum NfL levels. NfL may serve as a non-invasive biomarker for neurological complications in hypothyroid patients