How should I adjust levothyroxine (Synthroid) dose in an elderly woman taking 112 µg daily with elevated thyroid‑stimulating hormone?

Increase Levothyroxine Dose by 12.5–25 µg

In an elderly woman taking 112 µg of levothyroxine daily with a TSH of 9.63 mIU/L and normal T4 (1.23) and T3 (3.3), you should increase the levothyroxine dose by 12.5–25 µg and recheck TSH in 6–8 weeks. 1

Rationale for Dose Adjustment

• TSH >10 mIU/L warrants dose adjustment regardless of symptoms, as this level carries approximately 5% annual risk of progression to overt hypothyroidism and is associated with cardiac dysfunction and adverse lipid profiles 1
• The patient's TSH of 9.63 mIU/L is just below the 10 mIU/L threshold, but for patients already on levothyroxine therapy with TSH in the 4.5–10 mIU/L range, dose adjustment is reasonable to normalize TSH into the reference range (0.5–4.5 mIU/L) 1
• Normal T4 and T3 levels confirm this is subclinical hypothyroidism (elevated TSH with normal thyroid hormones), indicating the current dose is insufficient 1

Specific Dosing Strategy for Elderly Patients

• Use smaller increments (12.5 µg) for elderly patients or those with cardiac disease to avoid potential cardiac complications during titration 1
• Larger adjustments (25 µg) may be appropriate for patients <70 years without cardiac disease, but elderly patients require more conservative titration 1, 2
• The recommended increment for dose adjustment is 12.5–25 µg based on the patient's current dose to normalize thyroid function 1

Monitoring Protocol

• Recheck TSH and free T4 in 6–8 weeks after dose adjustment, as this represents the time needed to reach steady state 1, 3
• Target TSH should be 0.5–4.5 mIU/L with normal free T4 1
• Once adequately treated, repeat testing every 6–12 months or sooner if symptoms change 1

Age-Related Considerations

• Elderly patients require lower levothyroxine doses than younger patients to achieve the same TSH normalization 4, 5
• Studies show that patients over 60 years need approximately one-third less levothyroxine than previously recommended 5
• The current dose of 112 µg may already be approaching the upper limit for some elderly patients, making small incremental adjustments particularly important 2

Critical Safety Precautions

• Before increasing levothyroxine, confirm the patient does not have concurrent adrenal insufficiency, as thyroid hormone can precipitate adrenal crisis 1, 6
• Monitor for signs of overtreatment after dose adjustment, including tachycardia, tremor, or cardiac symptoms 7
• Avoid excessive dose increases that could lead to iatrogenic hyperthyroidism, which increases risk for osteoporosis, fractures, abnormal cardiac output, and ventricular hypertrophy 1

Common Pitfalls to Avoid

• Do not make larger dose adjustments (>25 µg) in elderly patients, as this risks cardiac complications 1, 2
• Do not recheck TSH before 6–8 weeks, as adjusting doses too frequently before reaching steady state can lead to inappropriate dosing 1
• Approximately 25% of patients on levothyroxine are unintentionally maintained on doses sufficient to fully suppress TSH, so careful monitoring after adjustment is essential 1
• Never assume the patient is non-compliant without first confirming adherence, as poor compliance is a common cause of persistent TSH elevation 1

Alternative Considerations

• If the patient has cardiac disease or multiple comorbidities, start with the lower increment (12.5 µg) to minimize cardiovascular risk 1, 2
• For patients with recent acute illness or hospitalization, consider waiting 4–6 weeks after recovery before adjusting the dose, as non-thyroidal illness can transiently affect TSH 1