What is the relationship between thyroid disease and hearing loss?

The Relationship Between Thyroid Disease and Hearing Loss

Thyroid disease is significantly associated with hearing loss, with hypothyroidism increasing the risk of hearing loss by 1.69-fold compared to individuals without thyroid dysfunction. 1 This relationship has important implications for patient care and quality of life.

Types of Hearing Loss in Thyroid Disease

Hypothyroidism

• Primarily causes sensorineural hearing loss (SNHL), though mixed hearing loss can also occur 2
• Hearing loss is typically bilateral (66.5% of cases) 3
• Affects multiple frequencies, but particularly impacts high frequencies (4000-8000 Hz) 4
• Prevalence of hearing loss among hypothyroid patients is approximately 24% 1

Hyperthyroidism (Graves' Disease)

• Associated with decreased hearing ability, particularly at high frequencies (4000-8000 Hz) 5
• Pure tone audiometric findings at 8000 Hz correlate positively with FT3, FT4 levels and negatively with TSH 5
• The odds ratio for having hearing loss at 8000 Hz in Graves' disease is 14.97 5

Pathophysiologic Mechanisms

1. Cochlear dysfunction: Thyroid hormone deficiency affects cochlear metabolism and function 2
2. Autoimmune mechanisms: Shared antigen targets between inner ear and thyroid gland in autoimmune thyroid diseases 3
3. Brainstem auditory pathway involvement: Prolonged absolute latency of wave V and interpeak latencies I-III and I-V on brainstem electric response audiometry 2
4. Middle ear involvement: Tympanogram abnormalities observed in some hypothyroid patients 2

Screening and Assessment

For patients with thyroid disease:

• Regular hearing assessment is recommended, particularly in:
  • Patients with 22q11.2 deletion syndrome (DiGeorge syndrome), who have higher rates of both thyroid dysfunction and hearing issues 6, 7
  • Patients with diabetes and thyroid disease (dual risk factors) 6
  • Post-thyroidectomy patients 7

For patients with hearing loss:

• Consider thyroid function testing, as approximately 7% of hearing-impaired individuals have hypothyroidism 1
• Evaluate for both conductive and sensorineural components 2

Treatment Considerations

Hormone Replacement Therapy

• Levothyroxine treatment for hypothyroidism can lead to statistically significant improvement in hearing thresholds on pure-tone audiometry 2
• Tympanogram curves may return to normal in most patients following thyroid hormone replacement 2
• However, brainstem electric response parameters may not show significant reversibility to normalcy after treatment 2

Autoimmune Thyroid Disease

• Important caveat: In autoimmune thyroid disease (AITD), levothyroxine alone may not prevent immune-mediated sensorineural hearing loss 3
• Corticosteroid therapy may be required to achieve hearing recovery in AITD patients with immune-mediated inner ear disease, even when they are adequately treated with levothyroxine 3

Monitoring Recommendations

1. For hypothyroid patients:

   • Baseline hearing assessment at diagnosis
   • Regular audiological follow-up, especially for those with autoimmune thyroid disease
   • Transient evoked otoacoustic emission (TEOAE) testing may detect audiological abnormalities at a higher rate than standard audiometry in euthyroid Hashimoto's thyroiditis 4

2. For patients with known hearing loss:

   • Assess hearing at least every 3 years in patients with known hearing loss or with reported concern for changes in hearing 6
   • Monitor for changes in hearing status following initiation of thyroid hormone replacement

Clinical Implications

1. Patients with thyroid disease should be educated about the potential risk of hearing impairment
2. Early identification and treatment of thyroid dysfunction may help prevent or minimize hearing loss
3. In patients with autoimmune thyroid disease and hearing symptoms, consider both thyroid hormone replacement and immunomodulatory therapy
4. For patients with both conditions, management should address both thyroid function and hearing rehabilitation to optimize quality of life

Remember that untreated hearing loss can lead to social isolation, emotional dysfunction, and decreased quality of life in older adults 6, making early detection and management crucial for patient well-being.