Can hypothyroidism cause peripheral neuropathy?

Can Hypothyroidism Cause Peripheral Neuropathy?

Yes, hypothyroidism is a well-established cause of peripheral neuropathy and should be routinely screened for in any patient presenting with neuropathic symptoms. 1, 2, 3

Mechanism and Clinical Presentation

Hypothyroidism causes peripheral neuropathy through multiple mechanisms, with the severity and type of neuropathy correlating with the duration and severity of thyroid hormone deficiency. 4, 5

The most common manifestations include:

• Carpal tunnel syndrome - the most frequent presentation, occurring due to median nerve compression from myxedematous tissue accumulation 2, 6
• Distal symmetric polyneuropathy - predominantly sensory, affecting lower limbs more than upper limbs, presenting with numbness, tingling, and paresthesias in a stocking-and-glove distribution 4, 5
• Sensorimotor axonal neuropathy - less common but can occur with prolonged untreated hypothyroidism 5

Electrophysiological Findings

Nerve conduction studies in hypothyroid patients demonstrate characteristic abnormalities even in early disease: 4

• Increased latencies in median, ulnar, tibial, and sural nerves
• Decreased conduction velocities across all tested nerves
• Decreased amplitudes in median, tibial, and sural nerves
• Pattern consistent with axonopathy rather than demyelination 5

Importantly, subclinical hypothyroidism can also cause peripheral neuropathy, with recent evidence showing subclinical carpal tunnel syndrome and peroneal neuropathy at the fibular head even in asymptomatic patients. 6

Diagnostic Approach

When evaluating peripheral neuropathy, hypothyroidism must be excluded as part of the initial workup. 1, 3

The diagnostic algorithm should include:

• Thyroid function testing (TSH and free T4) - mandatory in all patients with peripheral neuropathy, particularly those with carpal tunnel syndrome 2, 3
• Anti-TPO antibodies - positive correlation exists between TPO antibody levels and F-wave latency abnormalities in median and ulnar nerves 6
• Creatine kinase levels - correlate with peroneal nerve dysfunction severity 6
• Nerve conduction studies - to characterize the type and severity of neuropathy 4, 3

Treatment and Prognosis

Thyroid hormone replacement therapy is the definitive treatment and leads to improvement in both symptoms and electrophysiological parameters. 2, 5

Key treatment principles:

• Initiate levothyroxine replacement to normalize thyroid function
• Symptomatic improvement typically occurs within weeks to months of achieving euthyroid state 5
• Electrophysiological parameters improve with treatment, confirming the causal relationship 4, 5
• Earlier detection and treatment correlate with better neurological outcomes 4

Critical Clinical Pitfalls

Do not overlook hypothyroidism as a treatable cause of neuropathy. The European consensus on inflammatory bowel disease specifically lists hypothyroidism among the well-known risk factors that must be excluded before attributing peripheral neuropathy to other causes. 1

Screen for subclinical disease: Even patients with subclinical hypothyroidism (elevated TSH with normal free T4) can develop peripheral neuropathy, particularly entrapment neuropathies. 6

Monitor high-risk patients: Patients with autoimmune conditions, particularly those with positive anti-TPO antibodies, warrant closer monitoring for both thyroid dysfunction and neuropathic complications. 6