How to treat a patient with severe hypothyroidism (elevated Thyroid-Stimulating Hormone (TSH))?

Treatment of Severe Hypothyroidism with TSH of 45

Levothyroxine replacement therapy is the standard treatment for severe hypothyroidism with a TSH of 45, and should be initiated promptly to normalize thyroid function and improve clinical outcomes. 1, 2

Initial Assessment and Diagnosis

• A TSH of 45 mIU/L indicates severe primary hypothyroidism, which requires immediate treatment 1
• Confirm the diagnosis by measuring Free T4 levels, which will be low in overt hypothyroidism 2
• The most common cause of primary hypothyroidism is chronic autoimmune (Hashimoto's) thyroiditis 1
• Risk factors include female sex, advancing age, white race, type 1 diabetes, Down syndrome, family history of thyroid disease, and previous radiation therapy 1

Treatment Approach

Dosing Guidelines

• For young, healthy patients without cardiac disease:

  • Start with full replacement dose calculated at approximately 1.6 mcg/kg/day based on ideal body weight 2, 3
  • For example, a 70 kg patient would start with approximately 112 mcg daily 3

• For elderly patients (>70 years) or those with cardiovascular disease:

  • Begin with a lower dose of 25-50 mcg daily 2, 3
  • Gradually increase by 12.5-25 mcg every 4-6 weeks until reaching maintenance dose 3
  • This cautious approach reduces risk of precipitating cardiac events 3, 4

Administration Instructions

• Take levothyroxine as a single daily dose 5
• Administer on an empty stomach, 30-60 minutes before breakfast with a full glass of water 5
• Avoid taking with medications that can interfere with absorption, such as:
  • Iron supplements
  • Calcium supplements
  • Antacids
  • These should be separated by at least 4 hours from levothyroxine 5

Monitoring and Follow-up

• Check TSH and Free T4 levels 6-8 weeks after initiating therapy or changing dose 2, 3
• Target TSH level should be within the reference range (0.5-2.0 mIU/L) 3
• Free T4 can help interpret ongoing abnormal TSH levels during therapy, as TSH may take longer to normalize 2
• Once stable, monitor every 6-12 months 2, 6
• For persistent TSH elevation despite adequate replacement dose, consider:
  • Poor medication compliance
  • Malabsorption issues
  • Drug interactions 3, 7

Special Considerations

• Pregnancy: Women who are pregnant or planning pregnancy require close monitoring and often need increased levothyroxine dosing 5
• Elderly patients: Higher TSH targets may be appropriate (age-dependent upper limits can range up to 7.5 mIU/L for patients over 80) 8
• Coronary artery disease: Particularly careful dose titration is needed to avoid precipitating cardiac events 3

Potential Adverse Effects

• Overtreatment can lead to iatrogenic hyperthyroidism with symptoms such as:
  • Rapid or irregular heartbeat
  • Chest pain
  • Nervousness
  • Insomnia
  • Weight loss 5
• Long-term overtreatment increases risk of atrial fibrillation and osteoporosis 3
• Temporary hair loss may occur during the first few months of therapy 5

Patient Education

• Inform patients that levothyroxine replacement is typically lifelong 5
• Improvement in symptoms may take several weeks to notice 5
• Consistent daily administration is crucial for optimal results 5
• Patients should notify their healthcare provider about all medications they are taking, as dose adjustments may be necessary 5

With proper treatment and monitoring, most patients with severe hypothyroidism can achieve normal thyroid function and resolution of symptoms, significantly improving their quality of life and preventing long-term complications.