What is the treatment for hypothyroidism?

Treatment for Hypothyroidism

The standard treatment for hypothyroidism is levothyroxine (synthetic T4) therapy, which should be initiated for patients with TSH persistently >10 mIU/L or for symptomatic patients with any degree of TSH elevation. 1

Diagnosis and Assessment

• Confirm elevated TSH with repeat testing after 3-6 weeks, as 30-60% of high TSH levels normalize on repeat testing 1
• Measure both TSH and free T4 to distinguish between subclinical hypothyroidism (normal free T4) and overt hypothyroidism (low free T4) 1
• Hashimoto thyroiditis (autoimmune disease) is the cause of primary hypothyroidism in up to 85% of patients living in areas with adequate iodine levels 2

Treatment Algorithm Based on TSH Levels

• For patients with TSH >10 mIU/L: Initiate levothyroxine therapy regardless of symptoms 1
• For patients with TSH 4.5-10 mIU/L: Treatment decisions should be individualized based on symptoms, presence of anti-TPO antibodies, and other risk factors 1
• For symptomatic patients with any degree of TSH elevation: Consider levothyroxine therapy 1

Levothyroxine Dosing Guidelines

• For patients <70 years without cardiac disease: Initial full replacement dose of approximately 1.6 mcg/kg/day 1, 3
• For patients >70 years or with cardiac disease: Start with a lower dose of 25-50 mcg/day and titrate gradually 1, 4
• Pregnancy may increase levothyroxine requirements; monitor TSH levels and adjust dosage accordingly 5

Dose Adjustments and Monitoring

• Monitor TSH every 6-8 weeks while titrating hormone replacement 1, 2
• Once adequately treated, repeat testing every 6-12 months or if symptoms change 1
• Free T4 can help interpret ongoing abnormal TSH levels during therapy 1
• Target TSH levels should be within the normal reference range (0.4-4.0 mIU/L) 3

Risks of Inadequate Treatment

• Untreated hypothyroidism can lead to serious complications including:
  • Cardiovascular disease and increased mortality 3
  • Cognitive issues and memory problems 2
  • Reproductive health issues including infertility and increased risk of miscarriage 2
  • In severe cases, progression to myxedema coma (mortality rate up to 30%) 2

Risks of Overtreatment

• About 25% of patients on levothyroxine are unintentionally maintained on doses high enough to suppress TSH 6, 1
• Overtreatment can increase risk for:
  • Osteoporosis and fractures 6, 1
  • Abnormal cardiac output and ventricular hypertrophy 6
  • Atrial fibrillation, particularly in elderly patients 5

Special Populations

• Pregnant women:

  • Continue levothyroxine during pregnancy and monitor TSH levels closely 5
  • Untreated hypothyroidism during pregnancy is associated with complications including spontaneous abortion, gestational hypertension, and premature delivery 5

• Elderly patients:

  • Use lower starting doses (25-50 mcg/day) 1, 5
  • Monitor closely for cardiac effects 5

• Women planning pregnancy:

  • More aggressive normalization of TSH is warranted 1
  • Subclinical hypothyroidism during pregnancy is associated with adverse outcomes 1

Alternative Treatment Considerations

• While levothyroxine alone is the standard treatment, some studies have evaluated combination therapy with levothyroxine plus liothyronine (T3) 4
• Currently, until clear advantages of combination therapy are demonstrated, levothyroxine alone should remain the treatment of choice 4

Common Pitfalls to Avoid

• Failure to confirm elevated TSH with repeat testing before initiating treatment 1
• Inadequate dose adjustments leading to persistent hypothyroid symptoms 1
• Excessive dose increases that could lead to iatrogenic hyperthyroidism 1
• Not monitoring TSH levels regularly after initiating or changing therapy 2