Initial Management of Hypothyroidism
The initial management for hypothyroidism is levothyroxine (T4) replacement therapy, with a starting dose of 1.6 mcg/kg/day for young, healthy patients and a reduced dose of 25-50 mcg/day for elderly patients or those with cardiovascular disease. 1
Diagnosis and Assessment
Before initiating treatment, confirm the diagnosis with:
- Elevated TSH and low free T4 levels for primary hypothyroidism
- Morning laboratory testing (around 8 am) is recommended for accurate results
- For suspected central hypothyroidism, additional pituitary hormone testing may be needed
Levothyroxine Dosing Algorithm
Initial Dosing
- Young, healthy adults (<70 years without cardiac disease): 1.6 mcg/kg/day 1
- Elderly patients (>70 years): 25-50 mcg/day 1, 2
- Patients with coronary artery disease: Start with low dose (25-50 mcg/day) and gradually titrate 3
Special Populations
- Pregnant women: Promptly treat and adjust dose to maintain trimester-specific TSH reference range 2
- Children: Requires immediate treatment to prevent adverse effects on cognitive development 2
Monitoring and Dose Adjustment
- Check TSH and free T4 levels 6-8 weeks after initiating therapy 1
- Adjust dose to achieve target TSH range:
- After stabilization, monitor every 6-12 months 1
Clinical Pearls and Pitfalls
Common Pitfalls
- Overtreatment: Can increase risk of atrial fibrillation and osteoporosis, particularly in elderly patients 1, 2
- Undertreatment: May result in persistent symptoms and increased cardiovascular risk 4
- Drug interactions: Certain medications can interfere with levothyroxine absorption
Important Considerations
- Take levothyroxine on an empty stomach, 30-60 minutes before breakfast
- Avoid taking with calcium, iron supplements, or certain medications that can impair absorption
- Monitor closely during the first 2 weeks of therapy in infants for cardiac overload and arrhythmias 2
When to Consider Alternative Approaches
- For patients with persistent symptoms despite normalized TSH levels, consider:
- Checking for compliance issues
- Evaluating for malabsorption
- Assessing for drug interactions 5
While some studies have investigated combination therapy with levothyroxine plus liothyronine, levothyroxine monotherapy remains the standard treatment for hypothyroidism until clear advantages of combination therapy are demonstrated 6.