Can adequate treatment of hypothyroidism (underactive thyroid) with medications such as levothyroxine (thyroid hormone replacement) cause hoarseness in a general adult patient?

Can Adequate Treatment of Hypothyroidism Cause Hoarseness?

No, adequate treatment of hypothyroidism with levothyroxine does not cause hoarseness—in fact, proper treatment should resolve hoarseness if it was caused by the hypothyroidism itself. Hoarseness is a symptom of untreated hypothyroidism, not a side effect of its treatment 1, 2.

Understanding Hoarseness in the Context of Hypothyroidism

Hoarseness as a Symptom of Untreated Hypothyroidism

• Hoarseness is a classic manifestation of hypothyroidism itself, occurring due to myxedematous infiltration of the vocal cords and laryngeal structures 1, 2.
• The most common symptoms of hypothyroidism include fatigue, lethargy, cold intolerance, weight gain, constipation, change in voice (hoarseness), and dry skin 2.
• When hypothyroidism is adequately treated with levothyroxine, these symptoms—including hoarseness—should improve or resolve entirely 3, 2.

What Adequate Treatment Means

• Adequate treatment is defined as achieving a TSH within the reference range (0.5-4.5 mIU/L) with normal free T4 levels 4, 5.
• For most patients, this requires levothyroxine at approximately 1.6 mcg/kg/day, typically 75-100 mcg/day for women and 100-150 mcg/day for men 6.
• Treatment effectiveness should be monitored every 6-8 weeks during dose titration, then every 6-12 months once stable 4, 5.

When Hoarseness Persists Despite Treatment

Consider Inadequate Replacement

• If hoarseness persists, the first consideration should be whether the patient is truly adequately treated 4.
• Check TSH and free T4 levels—if TSH remains elevated above 4.5 mIU/L, the dose is insufficient 4, 5.
• Approximately 71% of patients on levothyroxine achieve euthyroid TSH levels, meaning 29% may be inadequately treated 7.

Evaluate for Alternative Causes of Hoarseness

The 2009 American Academy of Otolaryngology-Head and Neck Surgery guidelines provide a comprehensive framework for evaluating persistent hoarseness 8:

• Thyroid surgery complications: Thyroidectomy can cause hoarseness due to recurrent laryngeal nerve paralysis in up to 2.1% of patients 8.
• Medication-related causes: Review current medications, as certain drugs can cause hoarseness through various mechanisms (see Table 6 in the guidelines) 8.
• Structural laryngeal abnormalities: Patients with thyroid disease requiring surgery may have hoarseness and identifiable abnormalities on indirect laryngoscopy even before surgery 8.
• Other surgical history: Recent surgical procedures involving the neck, recent endotracheal intubation, or radiation treatment to the neck can all cause hoarseness 8.

Consider Overtreatment (Iatrogenic Hyperthyroidism)

• Overtreatment with levothyroxine occurs in 14-21% of treated patients and approximately 25% are unintentionally maintained on doses sufficient to fully suppress TSH 4, 5.
• While hoarseness is not a typical symptom of hyperthyroidism, excessive thyroid hormone can cause other complications including atrial fibrillation, osteoporosis, and cardiac dysfunction 4.
• If TSH is suppressed (<0.1 mIU/L), reduce levothyroxine dose by 25-50 mcg immediately 4.

Critical Clinical Algorithm

For a patient with hypothyroidism on levothyroxine who reports hoarseness:

1. Check TSH and free T4 levels immediately 4, 5

   • If TSH >4.5 mIU/L: Increase levothyroxine dose by 12.5-25 mcg 4
   • If TSH <0.1 mIU/L: Decrease levothyroxine dose by 25-50 mcg 4
   • If TSH 0.5-4.5 mIU/L: Treatment is adequate; look for other causes 4, 5

2. Obtain detailed history 8:

   • Duration of hoarseness (>2-3 weeks warrants laryngoscopy)
   • History of thyroid surgery or neck procedures
   • Recent endotracheal intubation
   • Current medications that may cause hoarseness
   • Tobacco use history

3. Consider laryngoscopy if hoarseness persists despite adequate thyroid hormone replacement 8

   • Vocal fold paralysis from surgical injury
   • Structural abnormalities
   • Vocal fold cancer (40% of patients wait >3 months before seeking care) 8

Common Pitfalls to Avoid

• Never assume hoarseness is from levothyroxine treatment itself—it is not a recognized side effect of adequate thyroid hormone replacement 3, 1, 2.
• Don't overlook inadequate treatment: Persistent hypothyroid symptoms including hoarseness indicate the need for dose adjustment, not discontinuation 4, 2.
• Failing to recognize surgical complications: If the patient has had thyroid surgery, recurrent laryngeal nerve injury must be considered 8.
• Ignoring the 40% of vocal fold cancer patients who delay seeking care: Persistent hoarseness >2-3 weeks requires laryngoscopic evaluation 8.