Neuromuscular findings in thyroid dysfunction: a prospective clinical and electrodiagnostic study

Area of Science:

• Endocrinology
• Neurology
• Internal Medicine

Background:

• Thyroid dysfunction, including hypothyroidism and hyperthyroidism, can manifest with various systemic symptoms.
• Neuromuscular involvement is a recognized but often underdiagnosed complication of thyroid disorders.

Purpose of the Study:

• To investigate the prevalence and characteristics of neuromuscular signs and symptoms in patients with newly diagnosed hypothyroidism and hyperthyroidism.
• To assess the impact of treatment on these neuromuscular manifestations.

Main Methods:

• A prospective cohort study involving adult patients with newly diagnosed thyroid dysfunction.
• Clinical evaluation using hand-held dynamometry and electrodiagnosis.
• Monitoring of clinical features, sensory signs, and biochemical data during treatment.

Main Results:

• Hypothyroid patients frequently reported neuromuscular complaints (79%), weakness (38%), sensorimotor axonal neuropathy (42%), and carpal tunnel syndrome (29%).
• Hyperthyroid patients experienced neuromuscular symptoms (67%) and weakness (62%), with weakness correlating with FT4 levels and resolving rapidly within 3.6 months.
• Sensorimotor axonal neuropathy was observed in 42% of hypothyroid and 19% of hyperthyroid patients, while carpal tunnel syndrome was only seen in hypothyroid patients.

Conclusions:

• Neuromuscular symptoms and signs are prevalent in newly diagnosed thyroid dysfunction.
• Hyperthyroid weakness appears functional and resolves completely with treatment, whereas hypothyroid weakness may suggest a more persistent myopathic process.
• Hand-held dynamometry is a valuable tool for detecting weakness and monitoring treatment efficacy in thyroid disease.