For an 83‑year‑old patient taking levothyroxine 25 µg each morning on an empty stomach with a TSH of 4.49 µIU/mL (upper normal) and normal free T4, should I continue the current dose and simply monitor?

Continue Current Dose and Monitor

For this 83-year-old patient on levothyroxine 25 µg daily with a TSH of 4.49 µIU/mL (just below the upper limit of normal) and normal free T4, you should continue the current dose and monitor TSH in 6–12 months rather than increase the dose. 1

Rationale for Maintaining Current Therapy

The patient's TSH of 4.49 µIU/mL falls within the normal reference range (0.45–4.5 µIU/mL), indicating adequate thyroid hormone replacement. 1 While this value sits at the upper boundary, it does not meet criteria for dose adjustment because:

• TSH values up to 4.5 µIU/mL are considered physiologically normal in adults, and the geometric mean TSH in disease-free populations is 1.4 mU/L. 1
• The normal TSH reference range shifts upward with advancing age—approximately 12% of persons aged 80+ with no thyroid disease have TSH levels >4.5 mIU/L. 1
• Free T4 is normal (7.9 µg/dL, reference 4.5–12.0), confirming adequate circulating thyroid hormone. 1

Why Not Increase the Dose

Increasing levothyroxine when TSH is already in the normal range would risk iatrogenic subclinical hyperthyroidism, which occurs in 14–21% of treated patients and increases risk for atrial fibrillation (3–5 fold), osteoporosis, fractures, and cardiovascular mortality—particularly dangerous in patients over 60 years. 1

Approximately 25% of patients on levothyroxine are unintentionally maintained on doses sufficient to fully suppress TSH, creating serious cardiovascular and bone complications. 1, 2

Monitoring Strategy

Once a stable levothyroxine dose achieves target TSH (0.5–4.5 µIU/mL), repeat TSH testing every 6–12 months, or sooner if symptoms change. 1, 2

For this 83-year-old patient:

• Recheck TSH in 6–12 months to ensure stability. 1
• If TSH rises above 4.5 µIU/mL on repeat testing, consider a small dose increase of 12.5 µg (given age >70 years). 1, 3
• Monitor for symptoms of hypothyroidism (fatigue, cold intolerance, constipation) or hyperthyroidism (palpitations, tremor, heat intolerance) at each visit. 1

Special Considerations for Elderly Patients

For patients over 70 years or with cardiac disease, smaller dose increments (12.5 µg) are recommended to avoid cardiac complications. 1, 3

Target TSH should remain within the reference range (0.5–4.5 µIU/mL), though slightly higher targets may be acceptable in very elderly patients to avoid overtreatment risks. 1

Common Pitfalls to Avoid

• Never adjust levothyroxine dose based on a single borderline TSH value—TSH secretion is highly variable and sensitive to acute illness, medications, and physiological factors. 1
• Avoid treating TSH values within the normal range, as this creates unnecessary risk of iatrogenic hyperthyroidism with its attendant cardiovascular and bone complications. 1
• Do not recheck TSH more frequently than every 6–8 weeks after dose changes, as levothyroxine requires 4–6 weeks to reach steady state. 1, 3