Conversation: The conversation between human and AI assistant.
[|Human|] I am 22 weeks pregnant, and the doctor wants to start me on PTU due to a low TSH. My T4 is normal and no one seems to be testing my T3. I am under the understanding that the goal of PTU is to regulate the active thyroid hormones, T3 and T4...if my T4 is normal (and provided my T3 is), why do I need the PTU?
[|AI|]  Hi, I have gone through the query and understood your concern. Propyl-thiouracil or PTU, is given to treat hyperthyroidism. The serum TSH levels are an earlier evidence of abnormal function than the value of the hormones T3 and T4 themselves. In fact, the absolute values of T3 and T4 can be done to assess the seriousness of the situation. If your TSH is within normal limits but on the lower side and if your absolute counts are normal, you do not need the medication, especially since it is not completely safe in pregnancy. Propylthoiuracil is preferable during the first trimester, while Methimazole is preferred during the later stages due to the hepatotoxicity of the former. Please get further help from your consultant. Take care.