What is DOC for treating thyrotoxicosis in a pregnant patient? and explain in detail?
Hyperthyroidism in pregnancy should be aggressively evaluated and treated. 
It is most commonly caused by Graves disease , but autonomously functioning nodules, gestational trophoblastic disease, thyroiditis, and hyperemesis gravidarum should also be considered. 
Hyperthyroidism is most difficult to control in the first trimester of pregnancy and easiest to control in the third trimester.
Methimazole crosses the placenta to a greater degree than propylthiouracil and has been associated with fetal aplasia cutis . 
Treatment of choice is propylthiouracil.
Radioiodine should not be used during pregnancy, either for scanning or treatment, because of effects on the fetal thyroid.