A woman with thyrotoxicosis and plans for pregnancy is most likely to be treated with what?

For a woman with thyrotoxicosis who is planning for pregnancy, the preferred treatment is propylthiouracil. This choice is based on its safety profile during the first trimester of pregnancy, as it has a lower risk of teratogenic effects compared to carbimazole. Propylthiouracil effectively reduces the production of thyroid hormones while posing a lesser risk to fetal development in early pregnancy.

During the first trimester, it is crucial to minimize any potential risks to the developing fetus, and propylthiouracil is recommended as it does not cross the placenta in significant amounts. As the pregnancy progresses, the treatment may shift to methimazole (which is similar to carbimazole) after the first trimester, but propylthiouracil remains the first-line treatment during early pregnancy.

Radioactive iodine is contraindicated in pregnancy due to its potential to harm the fetal thyroid gland, and the combination of carbimazole and thyroxine is not typically used in this situation since the primary goal is to manage thyrotoxicosis, not to provide thyroid hormone replacement. Therefore, propylthiouracil is the most suitable and safe option for managing hyperthyroidism in women who are planning to conceive.