Electromyographic Findings in Overt Hypothyroidism and Subclinical Hypothyroidism

Abstract

Objective: Hypothyroidism may cause neurologic signs and symptoms as it affects neuromuscular system in addition to many other systems. Subclinical hypothyroidism is the most common form of thyroid dysfunction and it may cause neuromuscular symptoms. In this retrospective study, we aimed to compare hypothyroid patients and healthy controls with normal thyroid function and without a disease-causing polyneuropathy, in terms of their neuromuscular symptoms and electromyographic (EMG) findings.

Methods: The patient group consisted of 31 overt hypothyroidic, 139 subclinic hypothyroidic patients and healthy control group consisted of 50 individuals with normal thyroid function and without a disease causing polyneuropathy, whom had EMG records for other reasons were included in the study. Neuromuscular symptoms, and neurological examination and electrophysiological findings were obtained from the patient records.

Results: In our study, we observed frequent neuromuscular complaints such as fatigue, morning stiffness, cramp, general pain and paresthesia in both overt and subclinic hypothyroidism patients. Carpal tunnel syndrome (CTS), was statistically higher in overt hypothyroidism group than in control group. Carpal tunnel syndrome was also observed more frequently in subclinic hypothyroidism group compared to control group but the difference did not reach statistical significance. We did not detect polyneuropathy in any group. The differences in motor nerve velocity and compound muscle action potential amplitudes were found to be statistically significant between hypothyroid and control group.

Conclusion: Involvement of motor fibers and neuromuscular areas in hypothyroidism due to reduced basal metabolism activity can show significant recovery following thyroid replacement therapy. We believe in the need for future studies comparing pre-treatment electrophysiological findings to post-treatment findings.