Levothyroxine Dose Adjustment for 78kg Patient with Increasing TSH
Increase the levothyroxine dose by 12.5-25 mcg daily and recheck TSH in 6-8 weeks. 1, 2, 3
Dose Adjustment Strategy
The recommended increment is 12.5-25 mcg based on the current dose and patient characteristics. 1 For a 78kg patient, this translates to:
- If the patient is under 70 years without cardiac disease: Use 25 mcg increments for more aggressive titration 1
- If the patient is over 70 years or has cardiac disease: Use 12.5 mcg increments to avoid cardiac complications 1, 3
Larger adjustments risk iatrogenic hyperthyroidism, which occurs in 14-21% of treated patients and increases risk for atrial fibrillation, osteoporosis, and cardiac complications. 1
Monitoring Protocol After Adjustment
Recheck TSH and free T4 in 6-8 weeks after the dose change. 1, 2, 3 This interval is critical because levothyroxine requires this time to reach steady state. 1 Adjusting doses more frequently before steady state leads to inappropriate dose changes. 1
Target TSH should be 0.5-4.5 mIU/L with normal free T4 levels. 1, 2 Once the appropriate maintenance dose is established, monitor TSH annually or sooner if symptoms change. 1, 3
Special Considerations Based on TSH Level
The degree of TSH elevation determines urgency:
- TSH >10 mIU/L: Increase dose regardless of symptoms, as this carries ~5% annual risk of progression to overt hypothyroidism 1, 4
- TSH 4.5-10 mIU/L: Dose adjustment is reasonable, particularly when approaching the upper end of this range 2
Critical Pitfalls to Avoid
Never make excessive dose increases. Approximately 25% of patients on levothyroxine are unintentionally maintained on doses sufficient to fully suppress TSH, increasing risks for atrial fibrillation (3-5 fold), osteoporosis, fractures, and cardiovascular mortality. 1, 4
For patients with cardiac disease or atrial fibrillation: Consider repeating testing within 2 weeks rather than 6-8 weeks if there are concerns about cardiac complications. 1
Before increasing the dose: Rule out concurrent adrenal insufficiency in suspected central hypothyroidism, as starting or increasing thyroid hormone before corticosteroids can precipitate life-threatening adrenal crisis. 1