Initial Treatment for Elevated TSH
Levothyroxine therapy is the initial treatment for patients with elevated TSH levels, with dosing based on the degree of TSH elevation, patient age, and comorbidities.
Assessment and Diagnosis
- Before initiating treatment, confirm elevated TSH with repeat testing after 3-6 weeks, as 30-60% of high TSH levels normalize on repeat testing 1
- Measure both TSH and free T4 to distinguish between subclinical hypothyroidism (normal free T4) and overt hypothyroidism (low free T4) 1
- The presence of anti-TPO antibodies indicates autoimmune etiology and predicts a higher risk of progression to overt hypothyroidism (4.3% vs 2.6% per year in antibody-negative individuals) 1
Treatment Algorithm Based on TSH Levels
- Initiate levothyroxine therapy regardless of symptoms for patients with TSH >10 mIU/L, as this level of elevation carries a higher risk of progression to overt hypothyroidism (approximately 5% per year) 1, 2
- For patients with TSH between 4.5-10 mIU/L and normal free T4, treatment decisions should be individualized based on symptoms, presence of anti-TPO antibodies, and other factors 1, 2
- Consider treatment for symptomatic patients with TSH between 4.5-10 mIU/L, as they may benefit from a trial of therapy 1, 3
Levothyroxine Dosing Guidelines
- For patients <70 years without cardiac disease or multiple comorbidities, start with full replacement dose of approximately 1.6 mcg/kg/day 4, 1
- For patients >70 years or with cardiac disease/multiple comorbidities, start with a lower dose of 25-50 mcg/day and titrate gradually 4, 1
- Elevated TSH can be seen in the recovery phase of thyroiditis; in asymptomatic patients with normal free T4, consider monitoring for 3-4 weeks before treating 4
Dose Adjustments and Monitoring
- Monitor TSH every 6-8 weeks while titrating hormone replacement 1
- Once adequately treated, repeat testing every 6-12 months or if symptoms change 1
- Development of low TSH on therapy suggests overtreatment or recovery of thyroid function; dose should be reduced or discontinued with close follow-up 4, 1
Special Considerations
- For women planning pregnancy, more aggressive normalization of TSH is warranted, as subclinical hypothyroidism during pregnancy is associated with adverse outcomes 1, 2
- In patients with both adrenal insufficiency and hypothyroidism, steroids should always be started prior to thyroid hormone to avoid an adrenal crisis 1
- Levothyroxine increases the response to oral anticoagulant therapy, so anticoagulant dosage may need to be reduced 5
- Addition of levothyroxine in patients with diabetes may worsen glycemic control and require adjustment of antidiabetic medications 5
Common Pitfalls and Considerations
- Overtreatment with levothyroxine risks development of subclinical hyperthyroidism in 14-21% of treated patients, increasing risk for osteoporosis, fractures, abnormal cardiac output, and atrial fibrillation 1, 3, 2
- Many drugs can affect levothyroxine absorption, including calcium supplements, iron supplements, proton pump inhibitors, and bile acid sequestrants; administer levothyroxine at least 4 hours apart from these agents 5
- Adjusting doses too frequently before reaching steady state (should wait 6-8 weeks between adjustments) is a common pitfall to avoid 1, 6
- About 25% of patients on levothyroxine are unintentionally maintained on doses sufficient to fully suppress TSH, highlighting the importance of regular monitoring 1