Initial Treatment for Hypothyroidism
The initial treatment for hypothyroidism is levothyroxine (T4) at a dose of 1.6 mcg/kg/day for patients under 70 years without cardiac disease, while elderly patients or those with cardiac conditions should start at a lower dose of 25-50 mcg/day. 1
Dosing Guidelines
The American College of Clinical Endocrinology recommends the following initial levothyroxine dosing:
- Standard adult dosing (under 70 years, no cardiac disease): 1.6 mcg/kg/day
- Elderly patients (>70 years) or with cardiac conditions: 25-50 mcg/day
- Target TSH range: 0.5-2.0 mIU/L for most adults 1
Pre-Treatment Considerations
Before initiating levothyroxine therapy:
- Rule out adrenal insufficiency, especially in cases of suspected hypophysitis
- Check ACTH and morning cortisol levels before starting thyroid replacement 1
- If multiple pituitary hormone deficiencies are present, obtain brain MRI with pituitary/sellar cuts 1
Medication Administration
- Take levothyroxine on an empty stomach, preferably 30-60 minutes before breakfast
- Avoid taking with calcium, iron supplements, or antacids as these can reduce absorption 1
- Several medications can affect levothyroxine absorption:
- Phosphate binders, bile acid sequestrants, ion exchange resins (administer levothyroxine at least 4 hours apart)
- Proton pump inhibitors, sucralfate, antacids (may reduce absorption)
- Orlistat (monitor thyroid function) 2
Monitoring and Dose Adjustment
- Repeat thyroid function testing 6-8 weeks after initiation of therapy 3
- Adjust dose in increments of 12.5-25 mcg based on TSH levels 1
- If TSH remains above reference range, increase thyroid hormone dose by 12.5-25 mcg 3
- Once stable, monitor every 6-12 months 1
Special Populations
Elderly Patients
- Start with lower doses (25-50 mcg/day)
- Increase gradually to avoid cardiac complications
- Target TSH may be higher (1.0-4.0 mIU/L) 1
Patients with Cardiac Disease
- Start with lower doses (25-50 mcg/day)
- Monitor closely for cardiac symptoms
- Increase dose gradually 1, 4
Pregnant Women
- Increase weekly dosage by approximately 30% (take one extra dose twice per week)
- Monitor monthly and adjust as needed
- Target TSH: 0.5-2.0 mIU/L 1, 4
Patients with Diabetes
- Monitor glycemic control closely when starting or adjusting levothyroxine
- Antidiabetic agent or insulin requirements may increase 2
Common Pitfalls and Considerations
- Overtreatment: Can lead to symptoms of hyperthyroidism, increased risk of atrial fibrillation, and osteoporosis 1
- Drug interactions: Many medications affect thyroid hormone pharmacokinetics; adjust timing of administration accordingly 2
- Persistent symptoms: Despite normalized TSH, some patients may continue to experience hypothyroid-like symptoms 5, 6
- Subclinical hypothyroidism: Generally, treatment is not necessary unless TSH exceeds 7.0-10 mIU/L 7
When to Consider Hospitalization
- Severe symptoms affecting activities of daily living
- Signs of myxedema
- Multiple pituitary hormone deficiencies 1
Levothyroxine monotherapy with appropriate dosing and monitoring remains the standard of care for hypothyroidism, with treatment goals focused on normalizing TSH levels and relieving symptoms 4, 6.