Endocrine Society Guidelines for Managing Hypothyroidism
Levothyroxine is the first-line treatment for hypothyroidism, with dosing based on patient characteristics and TSH monitoring every 6-8 weeks until stabilization, then annually thereafter. 1
Diagnosis and Initial Evaluation
- Hypothyroidism is diagnosed biochemically with elevated TSH and low free T4 levels 2
- Both TSH and FT4 should be measured in symptomatic patients to distinguish between primary hypothyroidism and central (pituitary) hypothyroidism 1
- Common symptoms include fatigue (68-83%), weight gain (24-59%), cognitive issues (45-48%), and menstrual irregularities (23%) 2
Treatment Recommendations by Patient Category
Overt Hypothyroidism
- Start levothyroxine at full replacement dose of 1.6 mcg/kg/day in young, healthy patients without cardiac disease 1, 3
- For elderly patients (>70 years) or those with cardiac disease, start with lower doses (25-50 mcg daily) and titrate gradually 1
- Full starting dose in cardiac asymptomatic patients is safe and may be more cost-effective than low-dose regimens 3
Subclinical Hypothyroidism
- TSH 4.5-10 mIU/L: Routine levothyroxine treatment is not recommended; monitor TSH every 6-12 months 1
- TSH >10 mIU/L: Levothyroxine therapy is reasonable to prevent progression to overt hypothyroidism 1
- Consider a trial of levothyroxine in patients with TSH 4.5-10 mIU/L who have symptoms compatible with hypothyroidism, but continue only if clear symptomatic benefit 1
Special Populations
Pregnancy
- Pregnant women or those planning pregnancy with elevated TSH should receive levothyroxine to restore TSH to reference range 1
- Monitor TSH every 6-8 weeks during pregnancy and adjust dose as needed 1
- Levothyroxine requirements often increase during pregnancy 1
Treated Hypothyroid Patients
- Adjust levothyroxine dose to maintain TSH within reference range 1
- When TSH is in upper half of reference range and symptoms persist, consider increasing dose to bring TSH to lower portion of reference range 1
Monitoring and Dose Adjustment
- Monitor TSH every 6-8 weeks after starting treatment or changing dose until TSH stabilizes within reference range 1, 4
- Once stabilized, check TSH annually or if symptoms change 1, 4
- FT4 can help interpret abnormal TSH levels during treatment, as TSH may take longer to normalize 1, 4
- Low TSH on therapy suggests overtreatment or recovery of thyroid function; reduce dose or discontinue with close follow-up 1, 4
Potential Complications of Untreated Hypothyroidism
- Increased risk of cardiovascular events and heart failure 2
- Insulin resistance and hyperglycemia in diabetic patients 2
- Reproductive health issues including disrupted ovulation, infertility, and increased miscarriage risk 2
- Severe hypothyroidism may progress to myxedema coma (mortality rate up to 30%) 2
Common Pitfalls to Avoid
- Failing to check both TSH and FT4 in symptomatic patients, which may miss central hypothyroidism 1, 4
- Overtreatment leading to iatrogenic hyperthyroidism, which occurs in 14-21% of treated patients 1
- Not adjusting dose in response to physiological changes throughout a patient's lifetime (pregnancy, aging, weight changes) 5
- Not considering drug interactions that affect levothyroxine absorption (iron, calcium supplements, antacids) 6
Administration Guidelines
- Take levothyroxine as a single dose on an empty stomach, 30-60 minutes before breakfast with a full glass of water 6
- Separate levothyroxine intake by at least 4 hours from agents that decrease absorption (iron, calcium supplements, antacids) 6
- Combination therapy with levothyroxine plus liothyronine currently shows no clear advantages over levothyroxine alone 7