Ms. Rodrigues, a 35 year-old woman, was recently given radioactive iodine for Graves’ disease, one month ago. She is now complaining of extreme fatigue, needing an extra sweater in the middle of summer, and constipation. She weighs 60 kg, with HR 54, BP 120/95, hoarse voice, and delayed biceps reflex relaxation. sTSH>100.
Write a prescription for her, and counsel her on taking the new medication.
Weight (kg) * 1.6
= 60 * 1.6 = 96 mcg
Therefore, take Levothyroxine 0.1 mg po daily.
Take with water on an empty stomach, no food for 30-60 minutes afterwards, take vitamins/iron/calcium at another meal.
How would you determine if this was a correct dose?
Check her sTSH 6 weeks later (half-life of T4 is 1 week, this will be just over 5.5 half-lives, at steady state).
What would you prescribe for her if she were 70 years old, or had angina?
Levo-thyroxine 0.025 mg po daily (increased by 0.025 mg daily every 4-6 weeks until sTSH is normal)