Endocrinology

PCP submission

37 yo female diagnosed with Graves disease at age 18 yo. Had radioactive iodine ablation at that time. Was initially treated with Levothyroxine but she continually had hypothyroid symptoms. She was then changed to Armour Thyroid about 15 years ago and felt much better. She was on 150 mg Armour Thyroid until 6 months ago when she lost her insurance. Armour Thyroid is unaffordable for her. I tried changing her back to levothyroxine 200 mcg but she developed the same hypothyroid symptoms as before. She is adamant that she needs Armour thyroid. While on Armour, her last TSH was 0.30 and Total T3 was 208 in Oct 2020. Her other usual labs are within normal range. She has not completed lab work since then due to financial and social constraints. Since stopping Armour, she has gained 15-20 pounds and BMI is now 34. She is having typical hypothyroid symptoms of cold intolerance, fatigue, increased sleep, decreased mood.

This is a trustworthy and reasonable patient. She is convinced that Armour is her only option. I know there are mixed reviews on it’s use and that Levothyroxine is preferred. What advise can you give me to piece together the ingredients to match 150 mg Armour thyroid, or how can I utilize levothyroxine better? Thank you for any help.

PCP submission

Thank you for this consult. Armour is ground up pig thyroid hormone with a ratio of T4 to T3 of 4:1 which is much more T3 than the physiologic ratio of about 13:1 for humans. A dose of 150 mg of Armour is roughly 250 mcg of levothyroxine. A calculated weight based dose of levothyroxine is about 1.7 mcg/kg – does that match up? I agree with your plan to add in synthetic T3 since she seems to need it. I think this is overall a safer approach as well. I would recommend starting with 175 mcg of levothyroxine and 5 mcg twice daily cytomel since the 250 mg of Armour was a bit too much. The cytomel is short acting which is reason for twice daily testing. Recheck TSH, FT4, and FT3 in about 6 weeks. Check it about 3-4 hours after the dose of cytomel in the morning. Now – also ask about pregnancy plans and contraception. Patient should be on levothyroxine ONLY during any pregnancy since T3 can not cross the blood brain barrier and fetus will be at risk if using any T3 preparation in place of adequate LT4. Hope this helps.