What is the appropriate starting dose of levothyroxine (T4) for a 60kg male with elevated Thyroid-Stimulating Hormone (TSH) level of 12?

Levothyroxine Dosing for 60kg Male with TSH 12

For a 60kg male with TSH 12 mIU/L, start levothyroxine at 96 mcg daily (1.6 mcg/kg/day), assuming age <70 years and no cardiac disease. 1, 2, 3

Initial Dose Calculation

• The full replacement dose is 1.6 mcg/kg/day for adults without cardiac disease or advanced age 1, 2, 3
• For this 60kg patient: 60 kg × 1.6 mcg/kg = 96 mcg daily 3
• Round to the nearest available tablet strength: 100 mcg daily is the practical starting dose 3
• TSH >10 mIU/L warrants immediate treatment regardless of symptoms, as this carries approximately 5% annual risk of progression to overt hypothyroidism 1

Age and Cardiac Considerations

If the patient is >70 years old OR has cardiac disease (coronary artery disease, arrhythmias, heart failure):

• Start at 25-50 mcg daily instead 1, 2, 3, 4
• Titrate by 12.5-25 mcg increments every 6-8 weeks 1, 2, 3
• This cautious approach prevents exacerbation of angina, arrhythmias, or heart failure 2, 5

If the patient is <70 years without cardiac disease:

• Use the full replacement dose of 96-100 mcg daily from the start 1, 3, 4
• More aggressive initial dosing is appropriate and safe in this population 1

Monitoring Protocol

• Recheck TSH and free T4 in 6-8 weeks after starting therapy 1, 2, 3
• Target TSH within the reference range (0.5-4.5 mIU/L) 1
• Adjust dose by 12.5-25 mcg increments based on TSH response 1, 2
• Once stable, monitor TSH every 6-12 months 1

Dose Adjustment Guidelines

• If TSH remains >10 mIU/L after 6-8 weeks: increase by 25 mcg 1
• If TSH 4.5-10 mIU/L: increase by 12.5-25 mcg 1
• If TSH <0.5 mIU/L: reduce dose by 12.5-25 mcg to avoid overtreatment complications 1, 2

Critical Pitfalls to Avoid

• Never start levothyroxine before ruling out adrenal insufficiency - this can precipitate adrenal crisis 1, 2
• Avoid overtreatment - suppressed TSH (<0.1 mIU/L) increases risk of atrial fibrillation, osteoporosis, and fractures, especially in elderly patients 1, 2, 5
• Do not adjust doses more frequently than every 6-8 weeks - levothyroxine takes 4-6 weeks to reach steady state 1, 3
• Confirm elevated TSH with repeat testing - 30-60% of elevated TSH levels normalize spontaneously on repeat measurement 1, 5

Special Circumstances

If cardiac disease is present:

• Start at 25-50 mcg daily 2, 3, 4
• Consider repeating TSH within 2 weeks if atrial fibrillation or serious cardiac conditions exist 1
• Use 12.5 mcg increments for titration 1, 2

If multiple comorbidities:

• Use the conservative approach with 25-50 mcg starting dose 1, 2
• Slower titration reduces risk of adverse effects 2