At what level of Thyroid-Stimulating Hormone (TSH) elevation should hypothyroidism be treated?

When to Treat Hypothyroidism

Treatment for hypothyroidism should be initiated for all patients with TSH >10 mIU/L, while those with TSH between 4.5-10 mIU/L should be treated selectively based on risk factors and symptoms. 1, 2

Diagnostic Confirmation

• Always confirm elevated TSH with repeat measurement after 2-3 months before initiating treatment 2
• Include free T4 measurement with repeat TSH to distinguish between subclinical (normal free T4) and overt hypothyroidism (low free T4) 1
• Check thyroid peroxidase antibodies to help predict risk of progression 2

Treatment Algorithm

Definite Treatment Indications:

1. TSH >10 mIU/L (with normal or low free T4) 1, 2
2. Pregnant women or women planning pregnancy with any TSH elevation 1
3. Symptomatic patients with overt hypothyroidism (elevated TSH with low free T4) 1

Selective Treatment (TSH 4.5-10 mIU/L):

• Age <65-70 years with:

  • Symptoms suggestive of hypothyroidism
  • Positive TPO antibodies
  • Goiter
  • History of Graves' disease
  • Infertility 1, 2

• Age >65-70 years:

  • Generally avoid treatment if TSH ≤10 mIU/L, especially in those >80-85 years 2
  • Consider treatment only if clear symptoms or cardiovascular risk factors 3

Treatment Approach

• Starting dose of levothyroxine:

  • Young adults: 1.5 μg/kg/day (typically 75-100 μg) 4
  • Elderly or patients with coronary artery disease: 12.5-50 μg/day 4, 5
  • Take on empty stomach, 30-60 minutes before breakfast 6

• Monitoring:

  • Check TSH 6-8 weeks after initiating therapy 6
  • Target TSH: 0.5-2.5 mIU/L for most adults 1, 2
  • For elderly patients, consider age-specific reference ranges 2, 3
  • Once stable, monitor TSH annually 2

Special Considerations

• Trial of therapy: For symptomatic patients with TSH <10 mIU/L, consider a 3-4 month trial; discontinue if no symptom improvement 2

• Transient hypothyroidism: Consider possibility of transient elevation in TSH (30-60% of elevated TSH levels normalize spontaneously) 5, 3

• Elderly patients: Upper limit of normal TSH increases with age (up to 7.5 mIU/L for those >80 years); avoid overtreatment 3

• Risks of overtreatment: Atrial fibrillation, osteoporotic fractures, especially in elderly 5

Common Pitfalls

• Treating based on single TSH measurement: Always confirm with repeat testing after 2-3 months 2, 3

• Attributing non-specific symptoms to mild TSH elevation: Treatment of subclinical hypothyroidism (TSH <10 mIU/L) often doesn't improve symptoms 5, 3

• Ignoring age-specific TSH reference ranges: Normal TSH increases with age; using standard ranges may lead to overdiagnosis in elderly 2, 3

• Overtreatment: Maintaining TSH below normal range increases risk of cardiac arrhythmias and bone loss 5