What is the treatment for subclinical hypothyroidism (SCH)?

Treatment of Subclinical Hypothyroidism

Levothyroxine therapy is not recommended for most patients with subclinical hypothyroidism who have TSH levels between 4.5 and 10 mIU/L, but is reasonable for those with TSH >10 mIU/L. 1

Diagnostic Approach

When subclinical hypothyroidism is suspected:

1. Confirm the diagnosis with repeat TSH and add FT4 measurement after 2-3 months
2. Evaluate for:
   • Signs and symptoms of hypothyroidism
   • Previous treatment for hyperthyroidism
   • Thyroid gland enlargement
   • Family history of thyroid disease
   • Review lipid profiles

Treatment Algorithm Based on TSH Level

TSH 4.5-10 mIU/L

• Standard recommendation: Monitor without treatment
  • Repeat thyroid function tests every 6-12 months
  • Only 2-5% progress to overt hypothyroidism annually 2
• Exceptions where treatment should be considered:
  • Pregnant women or those planning pregnancy
  • Symptomatic patients (trial of therapy)
  • Patients with positive TPO antibodies (higher risk of progression)
  • Patients with goiter

TSH >10 mIU/L

• Recommendation: Levothyroxine therapy is reasonable
• Rationale: Higher rate of progression to overt hypothyroidism (5%)
• Goal: Prevent manifestations and consequences of hypothyroidism

Special Populations

Pregnant Women

• Strong recommendation: Treat all pregnant women with subclinical hypothyroidism
• Rationale: Potential association with fetal wastage and neuropsychological complications 1
• Monitoring: Check TSH every 6-8 weeks during pregnancy
• Dosing: Requirement often increases during pregnancy 3

Elderly Patients (>80-85 years)

• Recommendation: Generally avoid treatment in oldest patients with TSH ≤10 mIU/L 4
• Rationale: Treatment may be harmful in elderly patients 5
• Approach: Use age-specific reference ranges (upper limit may be 7.5 mIU/L for patients >80 years) 5
• Caution: Start at lower doses (12.5-50 mcg/day) if treatment is necessary 6

Patients with Treated Overt Hypothyroidism

• Recommendation: Adjust levothyroxine dose to bring TSH into reference range
• Goal: TSH in lower half of reference range (0.4-2.5 mIU/L) for most adults 4

Treatment Implementation

Levothyroxine Dosing

• Standard starting dose: 1.5-1.8 mcg/kg/day for young adults 6
• Reduced starting dose: 12.5-50 mcg/day for:
  • Patients >60 years
  • Patients with coronary artery disease
  • Patients with long-standing severe hypothyroidism 2

Monitoring

• Recheck TSH 2 months after starting therapy 4
• Adjust dose to maintain TSH in lower half of reference range (0.4-2.5 mIU/L)
• Once stable, monitor TSH at least annually 4

Trial of Therapy for Symptomatic Patients

For patients with TSH 4.5-10 mIU/L and symptoms:

• Consider a several-month trial of levothyroxine
• Monitor for improvement in hypothyroid symptoms
• Important: Continue therapy only if clear symptomatic benefit
• Caveat: Difficult to distinguish true therapeutic effect from placebo effect 1

Common Pitfalls to Avoid

1. Overtreatment: Common in practice and associated with increased risk of atrial fibrillation and osteoporosis 2
2. Unnecessary treatment: 62% of elevated TSH levels may revert to normal spontaneously 5
3. Drug interactions: Iron and calcium reduce absorption; enzyme inducers reduce efficacy 7
4. Attributing non-specific symptoms to subclinical hypothyroidism: Treatment rarely helps symptoms in patients with minimal hypothyroidism 5
5. Failure to adjust for age: Using standard reference ranges for elderly patients may lead to overdiagnosis and overtreatment

Remember that the evidence does not support routine treatment of subclinical hypothyroidism with TSH <10 mIU/L in non-pregnant adults, as randomized controlled trials have not shown improvement in symptoms or cognitive function with treatment in this group 5.