11 weeks pregnant with low tsh levels

You need to become an empowered patient and in order to do this, you need to always get a paper copy of your lab tests, learn what the tests mean and keep your own file on them.  Your doctor should have done a thorough investigation for the cause of your hyperthyroidism.  It most often is caused by autoimmune diseases like Graves disease or Hashimoto's thyroiditis or a combination of both diseases as well as it could be caused just by a thyroiditis caused by a virus in which case it would be short-lived and will pass.  This can also be caused by thyroid nodules.  He should have tested you for Graves antibodies TSI and TRAb or in some cases TBII is done instead of the TRAb, as well as anti-TPO and TGAb for Hashimoto's.  Graves disease is an autoimmune disease where the antibodies attack the TSH receptor and Hashimoto's is an autoimmune disease where the antibodies attack the thyroid directly.  Also the usual lab tests to follow progress of treatment are TSH, Free T3 and Free T4.  I know many doctors do not do this but they should and this is what they do in Canada where I live.  If you have Graves disease, medication should not be discontinued until your antibody levels normalize, not just your thyroid lab tests.  In my case, I have been on antithyroid meds since 2007 decreasing levels as my labs improved and maintained on a low dose of meds.  The reaction you have to meds is common, especially if the dose given is too high.  The Propothiouracil drug you were currently given is the one approved for use in the first three months of pregnancy.  I believe after 3 months, they can switch to Carbimazole.  I found a combination of low dose of antithyroid meds plus added supplements helped me to go into remission.  Research studies have found that hyperthyroid patients often are low in carnitine levels (carnitine is an amino acid found in the body that helps with metabolism and levels are often low when patients are running hyper as they lose this from their muscles thru urination).  As well, vitamin D is extremely important as is Magnesium.  You can take suggested doses of these supplements to start. I asked my doc to test my levels in Total and Free Carntine, Vitamin D and Magnesium and I was deficient in all of these and used supplements.  The research study done on L-Carnitine and thyroid patients suggested a dose of 3,000 to 4,000 mg a day but I started at a low dose of 500 mg and raised it when I noted no ill effects from taking it.  If  you have Hashimoto's, you will control your levels best with the L-Carnitine and will only need a very minimal dose of antithyroid meds if at all.  One lady who posted to this Board was finally able to get control of her Hashimoto's disease with mostly the L-Carntiine alone.  If you have Graves, however, you will require at least a low dose of meds.