Treatment of Hypothyroidism
Levothyroxine sodium is the first-line medication for treating hypothyroidism, administered as a single daily dose on an empty stomach, 30-60 minutes before breakfast. 1, 2
Diagnosis and Evaluation
- Hypothyroidism is diagnosed biochemically with elevated TSH and low free T4 levels, indicating overt primary hypothyroidism 2
- Before initiating treatment, confirm elevated TSH with repeat testing along with free T4 measurement within 2-3 months of initial assessment 3
- Evaluate for signs and symptoms of hypothyroidism, previous thyroid treatment, thyroid enlargement, family history of thyroid disease, and review lipid profiles 3
Treatment Recommendations
Medication Selection
- Levothyroxine monotherapy remains the current standard for management of both primary and central hypothyroidism 4
- Liothyronine (T3) has a rapid onset and dissipation of action compared to levothyroxine, but the wide swings in serum T3 levels and possibility of more pronounced cardiovascular side effects limit its routine use 5
- Combined levothyroxine plus liothyronine treatment has been evaluated in multiple clinical trials, but until clear advantages are demonstrated, levothyroxine alone should remain the treatment of choice 6
Dosing Guidelines
- For adult patients with overt hypothyroidism, the initial dosage should be tailored to patient-specific factors 1, 2
- For mild hypothyroidism, the recommended starting dosage of levothyroxine is 25 mcg daily, which may be increased by up to 25 mcg every 1-2 weeks until maintenance dose of 25-75 mcg daily is reached 1
- For myxedema (severe hypothyroidism), start with 5 mcg daily, increasing by 5-10 mcg daily every 1-2 weeks until reaching 25 mcg daily, then increase by 5-25 mcg every 1-2 weeks until therapeutic response is attained (usual maintenance dose 50-100 mcg daily) 1
Treatment Based on TSH Level
- Levothyroxine therapy is recommended for patients with TSH > 10 mIU/L, even without symptoms 3, 8
- For patients with TSH between 4.5-10 mIU/L with normal free T4, routine levothyroxine treatment is not universally recommended 3
- Consider a trial of levothyroxine for patients with TSH 4.5-10 mIU/L who have symptoms compatible with hypothyroidism, continuing therapy only if clear symptomatic benefit is observed 3
Monitoring and Dose Adjustment
- Monitor TSH 6-8 weeks after initiating levothyroxine treatment or changing the dose 2
- For primary hypothyroidism, target TSH level is 0.5-2.0 mIU/L 4
- Annual TSH monitoring is recommended once the level is at goal to avoid overtreatment or undertreatment 2
- In central hypothyroidism, treatment is tailored according to free or total T4 levels, which should be maintained in the upper half of the normal range for age 4
Special Populations
- Pregnant women or women planning pregnancy should be treated with levothyroxine to restore TSH to reference range regardless of TSH level 3
- Monitor TSH every 6-8 weeks during pregnancy and adjust dose as needed, as levothyroxine requirements often increase during pregnancy 3
- For elderly patients, treatment should be initiated at a low dose to avoid potential cardiovascular complications 4
- Lifelong treatment with levothyroxine should normally only be considered in manifest hypothyroidism, while a wait-and-see strategy is advocated for milder subclinical forms to see if normalization occurs 8
Common Pitfalls and Caveats
- Overtreatment is common in clinical practice and is associated with increased risk of atrial fibrillation and osteoporosis 4
- Thyroid hormones, including levothyroxine, should not be used for obesity treatment or weight loss 1
- In patients with persistently elevated TSH despite an apparently adequate replacement dose, check for poor compliance, malabsorption, and drug interactions 4
- Distinguishing true therapeutic effect from placebo effect in patients with mild subclinical hypothyroidism can be difficult 3
- Administer levothyroxine at least 4 hours before or after drugs known to interfere with absorption 1