I had my thyroid removed, a yr. ago this month.  Since I was diagnosed with hyperthyroidism, 15 yrs. ago, I have constantly lost weight, which I find it very hard to put on the weight because I'm underweight for my height.  My synthroid is the correct dosage, through a lot of trial and error, and my TSH levels are within normal limits.  While I''m thankful to be healthy, I desire to gain at least twenty lbs. back but no matter how much I eat, I just have more BM's.  Please advise.