Just got back from my sixth month post op. I have been feeling horrible and didn't lose much weight. I have been taking thyroid medicine for 5 years and have been stable. However the labs show it is now worse than before and probably the reason I am shrinking but not losing pounds. They said it is rare for the thyroid to change after surgery, but it obviously can happen and derail all this hard work. Get a good aggressive doctor that will watch you closely. I should have been tested earlier but my symptoms were attributed to sides affects of gastric bypass not hypothyroidism. Hopefully on the right path now.