Okay I will. Thanks so much for responding back..
Make sure they test for Free T3 and Free T4, not Total T3 and Total T4. Most serum T3 and T4 is bound to protein and thus not biologically active. Only the small portion of thyroid hormone that is free of protein is biologically active. So, you need to know Free T3 and Free T4.
Okay will do I'll be returning to my endocrinologist soon..
Most likely it is not the medicine itself, but the effect on your thyroid hormone levels. Hyper patients frequently find that their dose is too high and their Free T3 and Free T4 levels drop too low in the range, thus causing hypo symptoms, that can include weight gain. If you will please post your thyroid test results, along with reference ranges we can better assess your status.