I have hypothyroid problem. I took lithium for a little while and it made it worse. Interesting thing though, BEFORE, I started lithium, my dr. looked at my blood work and said my thyroid numbers were already on their way to being in trouble and that I should be prepared for lithium to bring out the problem, to make it worse. It did. So now I'm on Synthroid forever. Even though I no longer take lithium.