Motherisk update: Managing hypothyroidism during pregnancy

QUESTION: One of my pregnant patients is taking levothyroxine for hypothyroidism. I prescribed her iron because she was anemic, but she continues to be weak and to have high levels of thyroid-stimulating hormone (TSH). Increasing her dose of levothyroxine did not seem to affect her TSH levels. ANSWER: Many women need higher doses of levothyroxine during pregnancy. You should continue to monitor her TSH levels carefully and be aware that iron given during pregnancy might form an insoluble complex with thyroxine in the gestational tract.