What is the recommended approach for ward-based management of hypothyroidism (underactive thyroid), including treatment and monitoring of patients with overt and subclinical hypothyroidism?

Ward-Based Management of Hypothyroidism

Initial Diagnosis and Confirmation

Measure TSH first, followed by free T4 to distinguish between subclinical hypothyroidism (elevated TSH, normal free T4) and overt hypothyroidism (elevated TSH, low free T4). 1

• Repeat abnormal TSH results after 2 weeks to 3 months before initiating treatment, as 30-60% of elevated TSH levels normalize spontaneously 2, 1
• Morning testing is preferred for more accurate results 1
• Measure anti-TPO antibodies to identify autoimmune etiology (Hashimoto's thyroiditis), which predicts 4.3% annual progression to overt hypothyroidism versus 2.6% in antibody-negative patients 2, 1
• Check lipid profile, as hypothyroidism affects cholesterol levels 1

Treatment Initiation Based on TSH Levels

TSH >10 mIU/L with Normal or Low Free T4

Initiate levothyroxine therapy immediately regardless of symptoms, as this threshold carries approximately 5% annual risk of progression to overt hypothyroidism. 2

Dosing for patients <70 years without cardiac disease:

• Start with full replacement dose of 1.6 mcg/kg/day 2, 3
• For new-onset hypothyroidism with TSH ≥10 mIU/L in pregnancy: 1.6 mcg/kg/day 3

Dosing for patients >70 years or with cardiac disease/multiple comorbidities:

• Start with 25-50 mcg/day and titrate gradually 2, 4
• Smaller increments (12.5 mcg) should be used to avoid cardiac complications 2
• Rapid normalization can unmask or worsen cardiac ischemia 2

TSH 4.5-10 mIU/L with Normal Free T4 (Subclinical Hypothyroidism)

Routine levothyroxine treatment is NOT recommended for asymptomatic patients in this range. 5, 2

Consider treatment in specific situations:

• Symptomatic patients with fatigue, weight gain, cold intolerance, or constipation 2
• Pregnant women or those planning pregnancy (target TSH <2.5 mIU/L in first trimester) 2, 3
• Patients with positive anti-TPO antibodies (4.3% annual progression risk) 2
• Patients with goiter or infertility 2

If not treating, monitor TSH every 6-12 months. 2

Critical Safety Considerations Before Starting Levothyroxine

Always rule out concurrent adrenal insufficiency before initiating thyroid hormone replacement, especially in suspected central hypothyroidism. 2, 1

• Starting thyroid hormone before corticosteroids can precipitate life-threatening adrenal crisis 2, 1
• In patients with both conditions, start physiologic dose steroids 1 week prior to thyroid hormone replacement 2

Monitoring and Dose Adjustment

Initial Monitoring Phase

Recheck TSH and free T4 every 6-8 weeks after any dose change until TSH reaches target range of 0.5-4.5 mIU/L. 2, 3, 6

• This 6-8 week interval represents the time needed to reach steady state 2
• Adjust levothyroxine by 12.5-25 mcg increments based on TSH results 2
• Larger adjustments may lead to overtreatment and should be avoided 2

Maintenance Monitoring

Once TSH is stable and within target range, monitor every 6-12 months or when symptoms change. 2, 3

• Free T4 can help interpret ongoing abnormal TSH levels during therapy 2
• Target TSH: 0.5-4.5 mIU/L for primary hypothyroidism 2, 4

Managing Overtreatment (TSH Suppression)

If TSH <0.1 mIU/L: Reduce levothyroxine dose by 25-50 mcg immediately. 2

If TSH 0.1-0.45 mIU/L: Reduce dose by 12.5-25 mcg, particularly in elderly or cardiac patients. 2

Risks of prolonged TSH suppression:

• 3-5 fold increased risk of atrial fibrillation, especially in patients >60 years 2
• Increased risk of osteoporosis and fractures, particularly in postmenopausal women 2
• Potential increased cardiovascular mortality 2
• Approximately 25% of patients on levothyroxine are unintentionally maintained on excessive doses 2

Special Populations

Pregnancy

For pre-existing hypothyroidism:

• Increase levothyroxine dose by 25-50% immediately upon pregnancy confirmation 2, 3
• Monitor TSH every 4 weeks until stable, then at minimum once per trimester 3
• Target TSH within trimester-specific reference range, ideally <2.5 mIU/L in first trimester 2, 3
• Reduce to pre-pregnancy dose immediately after delivery 3

Elderly Patients (>70 years)

• Start with 25-50 mcg/day 2, 4
• Use smaller dose increments (12.5 mcg) every 6-8 weeks 2
• Target TSH may be slightly higher (up to 5-6 mIU/L may be acceptable in very elderly patients to avoid overtreatment risks) 2

Cardiac Disease

• Start with 25-50 mcg/day 2, 4
• Obtain ECG to screen for baseline arrhythmias 2
• Monitor closely for angina, palpitations, or worsening heart failure 2
• Consider more frequent monitoring within 2 weeks for patients with atrial fibrillation or serious cardiac conditions 2

Common Pitfalls to Avoid

Do not treat based on a single elevated TSH value without confirmation testing. 2

Never start thyroid hormone before ruling out adrenal insufficiency in suspected central hypothyroidism. 2, 1

Avoid adjusting doses too frequently before reaching steady state—wait 6-8 weeks between adjustments. 2

Do not overlook transient causes of TSH elevation: acute illness, recent iodine exposure, recovery from thyroiditis, or certain medications 2

Undertreatment risks: persistent hypothyroid symptoms, adverse cardiovascular effects, abnormal lipid metabolism, and decreased quality of life 2

Overtreatment risks: iatrogenic hyperthyroidism occurs in 14-21% of treated patients, increasing risk for atrial fibrillation, osteoporosis, fractures, and cardiac complications 2