Levothyroxine Dose Increase to 112 mcg with 8-Week Follow-Up
Your approach of increasing levothyroxine to 112 mcg and scheduling follow-up in 8 weeks is appropriate and aligns with standard management guidelines for primary hypothyroidism with elevated TSH. 1, 2, 3
Rationale for the 112 mcg Dose Increase
The 12.5-25 mcg increment is the recommended standard for dose adjustments in patients with elevated TSH on levothyroxine therapy, which prevents overtreatment while effectively normalizing thyroid function. 1, 2
For patients with TSH >10 mIU/L (or persistently elevated TSH despite previous dose increases), a 25 mcg increment is reasonable, particularly in younger patients without cardiac disease. 1, 2
Larger dose jumps risk iatrogenic hyperthyroidism, which occurs in 14-21% of treated patients and increases risk for atrial fibrillation, osteoporosis, and cardiac complications. 1
The 8-Week Follow-Up Timing is Correct
Recheck TSH and free T4 in 6-8 weeks after any levothyroxine dose adjustment, as this represents the time needed to reach steady state given levothyroxine's long half-life. 1, 2, 3
Testing earlier than 6 weeks may show misleading results because steady state has not been achieved, leading to inappropriate further dose adjustments. 1, 3
The FDA label specifically recommends 6-8 week intervals for monitoring during dose titration in adults. 3
Target TSH Range
Aim for TSH within the reference range of 0.5-4.5 mIU/L with normal free T4 levels for primary hypothyroidism without thyroid cancer. 1, 2
Persistent TSH elevation above 4.5 mIU/L despite treatment indicates inadequate replacement and warrants further dose increases. 1, 2
Avoid over-replacement: approximately 25% of patients on levothyroxine are unintentionally maintained on doses high enough to suppress TSH completely, increasing serious complication risks. 1
Special Considerations That May Modify This Approach
For elderly patients (>70 years) or those with cardiac disease, use smaller 12.5 mcg increments and consider more frequent monitoring (within 2 weeks if cardiac disease or atrial fibrillation present). 1, 2, 3
For pregnant patients, increase by 12.5-25 mcg and monitor TSH every 4 weeks until stable, targeting TSH in the lower half of the reference range. 1, 3
If the patient has thyroid cancer, TSH targets differ based on risk stratification (0.1-0.5 mIU/L for intermediate-risk, <0.1 mIU/L for high-risk), requiring endocrinology consultation. 1, 2
Common Pitfalls to Avoid
Do not adjust the dose again before the 6-8 week mark, as adjusting too frequently before steady state leads to overcorrection and iatrogenic hyperthyroidism. 1, 3
If TSH remains elevated at 8 weeks despite good compliance, investigate malabsorption (celiac disease, H. pylori, gastritis), drug interactions (iron, calcium, PPIs), or consider switching to liquid levothyroxine formulation. 4, 5
Confirm medication adherence before increasing the dose further—poor compliance is a common cause of persistently elevated TSH. 6, 4
Rule out adrenal insufficiency in patients with autoimmune hypothyroidism before increasing levothyroxine, as thyroid hormone can precipitate adrenal crisis if cortisol deficiency exists. 1