What is the complete treatment protocol for patients with hypothyroidism, including recommended medications and dosages?

Treatment Protocol for Hypothyroidism

Levothyroxine is the first-line treatment for hypothyroidism, with dosing based on patient age, weight, and cardiovascular status. 1, 2, 3

Medication Selection

Primary Treatment

• Levothyroxine sodium (T4) is the standard treatment for hypothyroidism
  • Preferred due to consistent absorption and long half-life
  • Once-daily dosing is sufficient due to long half-life

Alternative/Adjunctive Treatments

• Liothyronine (T3) may be considered in specific situations:
  • During radioisotope scanning procedures
  • When impairment of peripheral conversion of T4 to T3 is suspected
  • Not recommended for routine use 4, 5

Dosing Protocol

Initial Dosing for Adults with Primary Hypothyroidism

1. Standard starting dose: 1.6 mcg/kg/day for most adults 1, 2, 6
2. Reduced starting dose for:
   • Elderly patients: 25-50 mcg/day 1, 2
   • Patients with cardiac disease or at risk for atrial fibrillation: 25-50 mcg/day 1, 2
   • Severe/longstanding hypothyroidism: Lower starting dose to prevent precipitating cardiac events

Initial Dosing for Special Populations

• Central hypothyroidism: Start with 1 mcg/kg levothyroxine 7

  • IMPORTANT: In central hypothyroidism, ensure cortisol replacement (hydrocortisone 15 mg AM, 5 mg at 3 PM) is initiated 1 week BEFORE starting thyroid hormone to prevent adrenal crisis 7, 1

• Myxedema: Start with 25-50 mcg/day and increase gradually 2

• Pediatric patients: Age-based dosing 2:

  • 0-3 months: 10-15 mcg/kg/day
  • 3-6 months: 8-10 mcg/kg/day
  • 6-12 months: 6-8 mcg/kg/day
  • 1-5 years: 5-6 mcg/kg/day
  • 6-12 years: 4-5 mcg/kg/day

  • 12 years but growth incomplete: 2-3 mcg/kg/day

  • Growth and puberty complete: 1.6 mcg/kg/day

Dose Titration and Monitoring

Titration Schedule

• Standard titration: Increase by 12.5-25 mcg every 4-6 weeks 1, 2
• Cautious titration (elderly/cardiac patients): Increase by 12.5-25 mcg every 6-8 weeks 1, 2

Monitoring Protocol

1. Initial follow-up: Check TSH and free T4 6-8 weeks after starting therapy or changing dose 1, 3
2. Subsequent monitoring:
   • Every 3 months during the first year
   • Every 6-12 months thereafter once stable 7, 1
   • More frequent monitoring for dose adjustments or clinical changes

Target Laboratory Values

• Primary hypothyroidism:

  • Target TSH: 0.5-2.0 mIU/L for most adults 1
  • Target TSH: 1.0-4.0 mIU/L for elderly patients 1

• Central hypothyroidism:

  • Do NOT use TSH for monitoring
  • Target free T4 in upper half of normal range 7, 2

Administration Guidelines

• Take levothyroxine on an empty stomach, 30-60 minutes before breakfast 2
• Separate from medications that interfere with absorption:
  • Iron supplements (4 hours)
  • Calcium supplements (4 hours)
  • Proton pump inhibitors (4 hours)
  • Antacids (4 hours)

Common Pitfalls and Caveats

1. Overtreatment risks:

   • Atrial fibrillation (3-fold increased risk with TSH ≤0.1 mIU/L in patients ≥60 years) 1
   • Osteoporosis and fractures
   • Increased all-cause mortality (up to 2.2-fold) in elderly with suppressed TSH 1

2. Undertreatment risks:

   • Persistent hypothyroid symptoms
   • Cardiovascular complications including heart failure 3
   • Metabolic issues including insulin resistance 3

3. Central hypothyroidism precautions:

   • CRITICAL: Always start cortisol replacement BEFORE thyroid hormone to prevent adrenal crisis 7, 1
   • Monitor free T4 rather than TSH for dosing adjustments 7, 2

4. Medication interactions:

   • Absorption decreased by food, coffee, calcium, iron, and certain medications
   • Effect altered by estrogens, androgens, and medications affecting hepatic metabolism

By following this protocol, hypothyroidism can be effectively managed with appropriate medication selection, dosing, and monitoring to optimize patient outcomes while minimizing risks.