Levothyroxine Dosing for Adult Hypothyroidism

Initial Dosing Strategy

For older adults (>50 years) or those with cardiac disease, start with 25-50 mcg/day and increase gradually at 6-8 week intervals 1
This cautious approach prevents exacerbation of underlying cardiac conditions, particularly coronary artery disease and arrhythmias 1

Adjust levothyroxine in 12.5-25 mcg increments based on TSH response and clinical status 1
For elderly or cardiac patients, use smaller 12.5 mcg increments to minimize cardiovascular risk 1

Always start corticosteroids several days before initiating thyroid hormone replacement to prevent precipitating adrenal crisis in patients with adrenal insufficiency 2, 1

Overtreatment increases risk for atrial fibrillation, osteoporosis, fractures, and cardiac complications 1
A suppressed TSH (<0.1 mIU/L) with elevated free T4 indicates tissue thyrotoxicosis and requires dose reduction 1
Persistent hypothyroid symptoms, adverse cardiovascular effects, abnormal lipid metabolism, and reduced quality of life result from inadequate dosing 1
TSH persistently >10 mIU/L despite treatment indicates insufficient replacement and requires dose escalation 1

Reduce or discontinue levothyroxine if TSH becomes suppressed, as this may indicate overtreatment or recovery of thyroid function 1