Hypothyroidism Management Guidelines
Levothyroxine is the standard first-line treatment for hypothyroidism, with dosing based on patient characteristics and TSH monitoring every 6-8 weeks until stabilized, then annually. 1, 2
Diagnosis and Assessment
- Confirm diagnosis with repeat TSH and free T4 measurements 2-3 weeks after initial assessment 1
- Consider anti-TPO antibody testing to identify patients at higher risk of progression to overt hypothyroidism (4.3% vs 2.6% per year in antibody-negative individuals) 1
- Evaluate for symptoms of hypothyroidism, which may include fatigue (68-83%), weight gain (24-59%), cognitive issues (45-48%), and menstrual irregularities (23%) 3
Treatment Recommendations Based on TSH Level
Overt Hypothyroidism (Elevated TSH with Low Free T4)
Subclinical Hypothyroidism (Elevated TSH with Normal Free T4)
- For TSH >10 mIU/L: Initiate levothyroxine therapy regardless of symptoms 1, 2, 4
- For TSH 4.5-10 mIU/L: Treatment generally not recommended unless specific risk factors are present 1, 2
- Consider treatment in patients with symptoms compatible with hypothyroidism, positive TPO antibodies, or goiter 1, 4
Levothyroxine Dosing Guidelines
Initial Dosing
- For adults <70 years without cardiac disease or multiple comorbidities: Full replacement dose of approximately 1.6 mcg/kg/day 5, 2, 6
- For adults >70 years or with cardiac disease/multiple comorbidities: Start with lower dose of 25-50 mcg/day and titrate gradually 5, 2, 6
- For pregnant women: Measure TSH and free T4 as soon as pregnancy is confirmed and during each trimester; maintain TSH in trimester-specific reference range 6
Dose Titration
- Adjust dosage by 12.5-25 mcg increments every 4-6 weeks until the patient is euthyroid 2, 6
- For patients with cardiac disease, titrate more slowly (every 6-8 weeks) 6
- Target TSH range of 0.5-2.0 mIU/L in primary hypothyroidism 1, 4
- For secondary or tertiary hypothyroidism, use free T4 levels (not TSH) to guide therapy, targeting the upper half of normal range 6
Monitoring Protocol
- Check TSH 6-8 weeks after initiating treatment or changing dose 2, 3
- Once stabilized, monitor TSH annually or if symptoms change 2, 3
- For patients on stable doses, monitor TSH every 6-12 months 1
Special Populations
Pregnant Women
- Treat subclinical hypothyroidism regardless of TSH level 1
- Target TSH in the lower half of the reference range 1
- Monitor TSH every 6-8 weeks during pregnancy and adjust dose as needed 1, 6
- Inadequate treatment during pregnancy is associated with increased risk of preeclampsia and low birth weight 2
Elderly Patients
- Use lower starting doses and titrate more gradually 6
- Treatment of subclinical hypothyroidism should probably be avoided in those aged >85 years with TSH up to 10 mIU/L 4
Common Pitfalls and Considerations
- Overtreatment: Can lead to subclinical hyperthyroidism in 14-21% of treated individuals, increasing risk of atrial fibrillation and osteoporosis 1, 4
- Undertreatment: Risks persistent hypothyroid symptoms, adverse effects on cardiovascular function, lipid metabolism, and quality of life 2
- Medication Interactions: Administer levothyroxine at least 4 hours before or after drugs known to interfere with absorption 6
- Food Interactions: Take on an empty stomach, as certain foods can affect absorption 6
- Elevated TSH despite adequate replacement: Consider poor compliance, malabsorption, or drug interactions 6, 4
- Development of low TSH on therapy: Suggests overtreatment or recovery of thyroid function; dose should be reduced or discontinued with close follow-up 5
Alternative Treatment Considerations
- Some patients (10-15%) on levothyroxine monotherapy report persistent symptoms despite normalized TSH 7, 8
- Combination therapy with levothyroxine plus liothyronine (T3) has been studied but clinical trials have not consistently demonstrated superiority over levothyroxine monotherapy 7, 9, 8
- Until clear advantages of combination therapy are demonstrated, levothyroxine alone should remain the treatment of choice 9