What is the treatment for hypothyroidism?

Treatment of Hypothyroidism

The principal treatment for hypothyroidism is oral levothyroxine sodium (T4) monotherapy, which should be initiated immediately upon diagnosis and generally continued for life. 1, 2

Diagnosis and Assessment

• Hypothyroidism is diagnosed biochemically with elevated TSH and low free T4 levels indicating overt primary hypothyroidism 2
• Before initiating treatment, confirm elevated TSH with repeat testing after 3-6 weeks, as 30-60% of high TSH levels normalize on repeat testing 3
• Measure both TSH and free T4 to distinguish between subclinical hypothyroidism (normal free T4) and overt hypothyroidism (low free T4) 3

Treatment Algorithm Based on TSH Levels

• Initiate levothyroxine therapy for all patients with:

  • Overt hypothyroidism (elevated TSH with low free T4) 1, 2
  • TSH persistently >10 mIU/L regardless of symptoms 3, 4
  • Any degree of TSH elevation with symptoms 3

• For subclinical hypothyroidism (elevated TSH with normal free T4):

  • TSH >10 mIU/L: Treatment recommended 4
  • TSH between 4.5-10 mIU/L: Treatment should be considered in symptomatic patients, patients with infertility, and patients with goiter or positive anti-thyroid peroxidase antibodies 4

Levothyroxine Dosing Guidelines

• For patients <70 years without cardiac disease:

  • Start with full replacement dose of approximately 1.6 mcg/kg/day 3, 5
  • This approach allows faster normalization of thyroid levels 3

• For elderly patients (>70 years) or those with cardiac disease:

  • Start with a lower dose of 25-50 mcg/day 3
  • Titrate gradually to avoid cardiac complications 3, 6
  • Lower starting doses are particularly important for patients with atrial fibrillation and coronary artery disease 2

Monitoring and Dose Adjustments

• Monitor TSH every 6-8 weeks while titrating hormone replacement 3, 2
• Once adequately treated, repeat testing every 6-12 months or if symptoms change 3
• The recommended increment for dose adjustment is 12.5-25 µg based on the patient's current dose 3
• Target TSH levels should be 0.5-2.0 mIU/L in primary hypothyroidism 4

Special Considerations

Pregnancy

• Pregnancy may increase levothyroxine requirements 6
• Monitor TSH levels and adjust dosage during pregnancy 6
• Return to pre-pregnancy dose immediately after delivery 6
• Untreated maternal hypothyroidism may have adverse effects on fetal neurocognitive development 6

Elderly Patients

• Initiate levothyroxine at less than the full replacement dose in elderly patients 6
• Atrial arrhythmias can occur in elderly patients with overtreatment 6
• Treatment of subclinical hypothyroidism should probably be avoided in those aged >85 years with TSH up to 10 mIU/L 4

Common Pitfalls and Considerations

• Overtreatment risks:

  • Iatrogenic hyperthyroidism 3
  • Increased risk for osteoporosis, fractures 3
  • Abnormal cardiac output or ventricular hypertrophy 3
  • Atrial fibrillation, especially in elderly patients 6

• Undertreatment risks:

  • Persistent hypothyroid symptoms 3
  • Adverse effects on cardiovascular function 3
  • Negative impacts on lipid metabolism and quality of life 3

• One quarter of patients on levothyroxine may be inadvertently maintained on doses high enough to make TSH levels undetectable 1

• If TSH remains elevated despite adequate replacement dose, check for:

  • Poor compliance 4
  • Malabsorption 4
  • Drug interactions 4

Long-term Management

• Levothyroxine treatment generally continues for life in patients with hypothyroidism 6, 7
• With appropriate treatment, symptoms of hypothyroidism can be effectively managed, and most people with the condition can lead normal, healthy lives 8
• Nearly one-third of patients with treated hypothyroidism may still exhibit symptoms despite normalized TSH levels 5